The Flash

Barry Allen, a forensic crime scene assistant for Central City Police Department, is struck by lightning during a storm that is created after a particle accelerator from S.T.A.R. Labs explodes. In a coma for nine months, Barry awakens in S.T.A.R. Labs, having been placed in the care of S.T.A.R. Labs founder Harrison Wells and his assistants Dr. Caitlin Snow and Cisco Ramon. Barry learns that he can move at extraordinary speeds, and that there were other "metahumans" created from the explosion. One of them, Clyde Mardon, is robbing banks with his ability to control the weather. In order to stop Mardon, Barry is outfitted with a suit, designed by Cisco, that can withstand his high speed. He tracks down Mardon and with Detective Joe West, who learns of Barry's abilities, Barry is able to stop Mardon, who is killed by Joe. With his new powers, Barry vows to exonerate his father, Henry, who is incarcerated for the accusation of murdering his wife, Nora, whom Barry witnessed being killed by another metahuman. He chooses the alias "Flash" for his alter ego. Wells, secretly revealed to be neither paraplegic nor needing glasses, reads a newspaper from 2024 stating the missing status of the Flash.

In flashbacks, it is revealed that Joe became Barry's legal guardian but did not let him visit Henry in prison at the latter's request. Barry begins using his abilities to stop minor crimes and help citizens across the city while starting to develop debilitating side effects. While guiding Iris West, who seeks his help to do her school assignment, Barry witnesses a robbery by a crew of men, but passes out while trying to stop them. The S.T.A.R. Labs team determines that Barry becomes hypoglycemic from the use of his abilities due to a sped-up metabolism and needs to ingest more calories to maintain his energy level. The team eventually learns that there is actually one robber, Danton Black, who has the ability to create clones of himself. Black intends to kill his former employer Simon Stagg, who stole Black's cloning research. With encouragement from Joe, Barry goes after Black and successfully stops him. However, Black commits suicide. Afterward, Barry accepts Joe's help in the investigation of Nora's murder. Later, Wells visits Stagg, who has already become obsessed with the Flash and plans to exploit them as he did to Black. Wells then kills Stagg.

As the police investigate the murder of one of the city's crime families, Barry suspects that the killer may be a metahuman who can control poison gases. As Barry and Joe work to discover the killer's identity, Wells and his team work to retrofit the particle accelerator into a prison for metahumans where they can begin to find a way of reversing their mutations. This brings up difficult feelings and memories for Snow, whose fiancé, Ronnie Raymond, was killed by the explosion. The team identifies the killer as Kyle Nimbus, discovering that Nimbus does not control gases, but transforms his body into them. The team learns that Joe, the lead detective in the original case, is Nimbus' next target. Barry races to Iron Heights Prison to save Joe's life, forcing Nimbus to overexert himself so that he can apprehend him. The team locks Nimbus into a cell they have made. In a flashback to when the accelerator explodes, Wells is seen going into his hidden room and viewing a surveillance video of Barry getting struck by lightning in his lab.

Wells begins testing Barry's powers by having him perform multiple tasks at superspeed. In the middle of the tests, a group of men attempt to hijack an armored truck carrying a diamond. Barry races over and stops the crime, as well as identifying Leonard Snart from a set of police mugshots. Felicity Smoak arrives to check on Barry, after learning that he woke from his coma. Barry introduces her to his friends at S.T.A.R. Labs. To combat the Flash, also known as the "Streak", Snart acquires stolen tech from S.T.A.R. Labs, which includes a cryonic gun. Cisco reveals to Barry that he created the gun as a fail-safe against Barry should he become a villain like the other metahumans they have encountered. Felicity helps the team locate Snart, who sets a trap for Barry. Cisco, Caitlin, and Felicity arrive in time to save Barry, and Snart is able to escape. Joe finally accepts Iris's relationship with Eddie Thawne, his partner. Wells demands Cisco not to build another fail-safe against Barry again. Barry kisses Felicity goodbye. Later, Snart tracks down his former partner, who has an affinity for fire, and offers him a place by Snart's side taking back Central City from the Flash.

Bette Sans Souci, a metahuman with the ability to turn anything she touches into an explosive, appears in Central City. She is being hunted by General Wade Eiling, and is a former military explosives expert. Barry brings her to S.T.A.R. Labs where the team explains to her that she was changed by the particle accelerator, which bonded bomb shrapnel to her body on a cellular level; and they cannot reverse the process. Secretly, Wells convinces Bette to kill Eiling. Barry races to stop her, and Eiling shoots her, who dies after mentioning Wells' name. Her body turns into a bomb. Barry speeds off with the body and drops it in the river to save the city from the massive explosion. Eiling visits Wells, demanding that they work together once again, this time to collect metahumans. Wells refuses and warns Eiling to never return to S.T.A.R. Labs. Meanwhile, Barry ends his friendship with Iris after she refuses his advice not to write about the "Streak". In a flashback set five years previously, Wells tells Eiling he is ending their experiments. After Eiling leaves, Wells walks to a cage and tells Gorilla Grodd that he has plans for him.

Barry speeds off to stop a car thief; but the thief's skin turns to steel and Barry breaks his hand while punching. He runs back to the lab before he can be hurt further. The thief is identified as Tony Woodward, Barry's childhood bully. Back at the lab, Cisco determines that if Barry can hit Woodward with a specific velocity at right angle, then he can create enough force to compromise Woodward's metal structure. Woodward kidnaps Iris and demands that she write about him. Barry arrives and manages to temporarily disable Woodward's abilities. Afterward, Woodward is locked away at S.T.A.R. Labs and finds out that Barry is the Flash, the name Iris also uses in her blog on the advice of Barry, who reconciles with her. Meanwhile, Joe continues investigating Nora's murder and gets suspicious of Wells, who opened S.T.A.R. Labs one month after Nora's murder; but Wells states that he came to Central City because of his wife's death. Joe, convinced that Wells is not involved, is visited by the metahuman that killed Nora, stealing the case file and threatening Iris's life if Joe does not drop his investigation.

Wells returns to his secret room, where it is revealed that he has been documenting Barry's abilities, and using his artificial intelligence, Gideon, to look at events in the future. Barry arrives at a crime scene where the victim was murdered via electrocution, and charred beyond recognition, suggesting a metahuman was involved. While investigating the victim's identity, the team identifies a power drain in the city. When Barry arrives, he is attacked by Farooq Gibran, a man who has the ability to siphon electrical energy. The attack drains Barry of his speed, and Gideon reveals to Wells that there are currently no references to the Flash in the future. Wells realizes that Barry's problem is psychological. Gibran attacks S.T.A.R. Labs , kills Woodward and Wells' life gets in danger, forcing Barry to overcome his fear, connect to his speed and kill Gibran. Meanwhile, Tockman starts a hostage crisis at a police station and critically shoots Eddie; but Iris manages to stop him and he is rearrested. Later, Wells sees that the timeline is safe, and takes a sample of Gibran's blood to determine how he was able to drain Barry's abilities.

Eddie proposes a task force to hunt down the Flash. A new metahuman, Roy Bivolo, shows up with the ability to send people into an uncontrollable rage, and uses his ability to rob a bank. Oliver Queen informs Barry that he and his team are tracking a killer who uses lethal boomerangs. Barry and Oliver agree to team-up and catch each other's targets. Barry decides to go after Bivolo by himself. Bivolo uses his abilities on Barry; but because of Barry's powers it makes the effects last longer. Oliver tries to stop Barry, and the two engage in a fight until Wells and Joe use colored strobe light to reset Barry's emotional state. Afterward, Barry and Oliver capture Bivolo and place him in the prison at S.T.A.R. Labs. Eddie's task force is established after he was beaten by an enraged Flash. Barry confirms Oliver's belief that he has a lot to learn. Oliver advises him to stay away from Iris, whom Barry is in love with. Iris decides to end her support of the Flash. Oliver asks Barry's team to keep his alter ego a secret. A new metahuman able to manipulate fire appears in Central City. This episode begins a crossover event that concludes on Arrow season 3 episode 8.

The yellow-suited speedster who killed Nora Allen returns, in search of Mercury Lab's tachyon particle technology. Barry encounters the "Reverse-Flash" and engages him but is swiftly defeated, with the villain insinuating that he and Barry have been lifelong enemies. Ronnie is revealed as the flame-controlling metahuman, suffering from memory-loss after having survived the explosion. Per Henry's advice, Barry confesses his love for Iris before the tachyon particle technology is used as bait to lure the Reverse-Flash into a trap. The villain manages to escape, however, and proceeds to attack Wells and the police, mysteriously sparing Eddie before engaging in Barry again. Ronnie appears and fends off the Reverse-Flash before they both flee the scene. Joe tells Eddie about metahumans and asks him to keep it a secret. Cisco realizes that there were two speedsters in Barry's house the night Nora died. Later, Wells enters his secret room and reveals the Reverse-Flash suit in a hidden chamber. Wells places the stolen tachyon device on it, and speaks in the villainous speedster's distorted voice, revealing himself to be the Reverse-Flash.

As Barry works on improving his speed through various training exercises, Leonard Snart returns to Central City with the cold gun and a new partner, Mick Rory, to set a trap for the Flash. Barry discovers his plan, and agrees with Wells not to engage Snart in the hope that he goes away and no one gets hurt like the last time. Snart and Rory, who now has a gun that can emit absolute hot temperatures, kidnap Caitlin to force Barry out of hiding. Cisco and Barry find a way to defeat Snart and Rory. The Flash faces the duo in the city for a showdown, exposing himself to the public. Barry eventually gets them to cross their streams with Eddie's help, successfully damaging the weapons and disabling the pair, who are arrested and the guns delivered to S.T.A.R. Labs. While in transport to Iron Heights, Snart and Rory are broken out by Snart's sister. Meanwhile, Caitlin investigates the cause of Ronnie's transformation and finds out that the Army is covering up the incident. After Iris moves in with Eddie, Barry decides to move back in with Joe.

While home, Wells receives a threatening call from an unidentified person before using his super speed to save his life from an attempt. Wells informs Barry and the team that the caller was Hartley Rathaway, a former protégé. Rathaway begins attacking his family's business with sonic blasts, and after Barry stops him, Rathaway reveals that he knows a secret of Wells', who states that Rathaway warned him that the particle accelerator could explode, but Wells chose to risk it for the rewards. Cisco discovers that Rathaway intentionally got caught so he could steal information from S.T.A.R. Labs that would allow him to identify the frequency of Barry's molecules so he can kill him. A trap set by Rathaway starts shredding Barry's organs. Wells manages to disable Rathaway's weapons. Later, Joe has Eddie start an investigation into Wells. Rathaway, imprisoned back in the particle accelerator, reveals to Cisco that he knows where Ronnie is and how to save him. In his secret room, Wells uses the tachyon technology to temporarily recharge his speed force energy. Meanwhile, Iris starts working as a journalist and realizes that she is hired to write about the Flash.

A woman with the ability to teleport to any location she can see breaks into Iron Heights and frees her boyfriend, Clay Parker. The S.T.A.R. Labs team identifies the woman as Shawna Baez. To help Barry, Henry tracks down leads in Iron Heights and finds out that Parker owed money to a local crime boss and is planning a heist to pay it back. Barry learns the location of the heist, finding Baez and Parker and is able to capture her after removing all the lights in a tunnel, effectively making her unable to teleport without being able to see. Parker manages to escape. Meanwhile, Cisco brings Rathaway out of his cell so that the latter can show the truth about Ronnie; Rathaway reveals that Doctor Martin Stein, who developed research into a F.I.R.E.S.T.O.R.M. project focused on transmuting elements, was at S.T.A.R. Labs the day of the explosion. Rathaway reveals that during the explosion Ronnie and Stein merged, before he escapes Cisco's custody. Barry starts dating Iris's colleague, Linda Park. Henry insinuates to Barry that he knows Barry's alter ego. Elsewhere, two city workers are attacked by Grodd.

The team attempts to track Stein's whereabouts after he attacks a scientist. They convince Stein into coming back to S.T.A.R. Labs for testing. Wells discovers that Ronnie and Stein's atoms are in conflict, and if it continues they will become nuclear. Stein leaves for a secluded location to safely explode without casualties. Barry and Caitlin arrive and use a device Wells made from the tachyon to separate the bodies, but it apparently does not work, and the duo escapes the explosion, which alerts Eiling, who orders a team to recover "Firestorm". Meanwhile, Joe enlists Cisco's help to identify Nora's murderer. The duo searches the house and finds blood from two people behind some new wallpaper. Joe asks Cisco to compare the blood to Wells'. Cisco runs the blood and informs Joe that while neither is from Wells, one is from an adult Barry. In the meantime Linda believes Barry to be still in love with Iris, but he proves to Linda that he now loves her not Iris.

Barry and Caitlin find Ronnie and Stein alive and separated, which Eiling also finds out. Joe reveals his findings to Barry. Ronnie and Stein realize that their minds are partially connected. Wells visits Eiling, who reveals that he knows Barry's alter ego and demands the F.I.R.E.S.T.O.R.M. project. Wells gives up Stein, who is tortured by Eiling until Barry and Ronnie save him. Ronnie and Stein reunite by the tachyon piece to survive the military onslaught. The duo gains enough control to be able to merge and separate on command. They decide to leave Central City to stay ahead of Eiling and learn more about their new powers. As the Reverse-Flash, Wells kidnaps Eiling and brings him to the sewers. He reveals himself to Eiling, and allows Grodd, who is displaying psychic abilities, to drag Eiling deeper into the sewer. Meanwhile, Iris's colleague, Mason Bridge tells her his belief that Wells deliberately caused the S.T.A.R. Labs explosion. Iris suspects Caitlin's activities and decides to help Mason with his investigation. Barry tells Joe that he will travel back in time again to save Nora, but intends to succeed by learning the mistakes in his previous attempt.

Mark Mardon, Clyde's brother, returns to Central City to avenge Clyde's death. Eddie and Linda get jealous of the intimacy between Barry and Iris. Mason shares his knowledge that Wells killed Stagg with Iris and Barry, who tells Caitlin and Cisco, who begins to believe Joe was right about Wells, so he rechecks the containment field that failed to hold the Reverse-Flash. Wells arrives and reveals himself to be Eobard Thawne, a relative of Eddie's and a man from the future who came back in time to kill Barry, and has since been stranded in the present day. Thawne also explains that he is pushing Barry to get stronger so that he can use Barry's powers to return to his time, and he murders Cisco to protect his secret. Mardon kidnaps Joe and forces him to watch as Mardon creates a tsunami in order to kill Iris. Barry reveals his secret identity to Iris, just after they admit to romantic feelings for each other, in order to save the city. Barry runs back and forth across the coastline to create a barrier against the tsunami, but he runs so fast that he travels back in time to the day before.

Thawne warns Barry not to change any event for fear that he will create a bigger problem. Barry does not listen and instead captures Mardon and puts him in the particle accelerator. Snart and Rory return to Central City. Snart sends his sister, Lisa after Cisco, whom they force to rebuild the cold and heat guns, and a third gun shooting gold for Lisa, by threatening to kill Cisco's brother. Iris rejects Barry's romantic approach and later Eddie punches him. Barry realizes that Thawne was right about not to manipulate the timeline. Cisco returns and reveals that Snart forced him to reveal the Flash's true identity. Barry goes after Snart, and the two come to a truce: Snart will not reveal Barry's identity, will no longer kill innocent people, and stay away from Barry's loved ones in exchange for Barry not locking him away in the particle accelerator. Caitlin tells Eddie and Iris that Barry is suffering from psychosis as a result of the lightning, making the duo reconcile with him and settling the tension. The Reverse-Flash kills Mason and destroys the evidence linking Thawne to Stagg's death. Mason's vanishing causes Barry to accept Joe was right about "Wells".

Barry and Joe go after terrorist Axel Walker, under the alias Trickster. Walker sets a diversion for the Flash and breaks James Jesse, the original Trickster from 20 years prior, out of prison. Jesse and Walker attempt to extort patrons of fundraiser by poisoning them and ransoming the antidote. When the Flash arrives, Jesse and Walker fit him with a bomb that will detonate if he stops moving. Thawne coaches Barry on how to vibrate his molecules so that he can phase through objects, which removes the bomb. Afterward, Barry provides an antidote to all the patrons before capturing Jasse and Walker. The Flash reveals his identity to Eddie and convinces him to keep Iris from investigating Mason's disappearance. Barry tells Eddie and Joe that "Wells" is the Reverse-Flash. In flashbacks, after failing to kill Barry, the Reverse-Flash escapes only to lose his speed. Gideon informs him that traveling through time has drained his powers. Thawne kills Harrison Wells and steals his appearance and identity so he can develop the particle accelerator sooner and return to his timeline.

As Barry works in conjunction with Joe and Eddie to stop crimes across the city, an engineering professor is killed by a swarm of bees at a university. While the team searches for a metahuman that can control bees, Felicity arrives with Ray Palmer, looking for assistance to improve his A.T.O.M. suit. The team tracks another bee attack, but Barry is too late and is attacked by the swarm. The team captures one of the bees, which turns out to be a robot and their suspect just a scientist from Mercury Labs named Brie Larvan, who is targeting other former employees. During the next bee attack, Barry goes after Larvan while Ray attempts to stop the bees from killing Dr. Tina McGee. Felicity disables the robots, and Barry captures Larvan. Tina tells Barry that "Wells" personality changed after his wife's demise. Iris threatens Eddie to break up if he does not share his secret. Barry informs Caitlin and Cisco about "Wells". She does not want believe it, but Cisco does, revealing that he has been having "dreams", which show his final moments with Thawne in the alternate timeline.

Barry and Eddie track a metahuman named Hannibal Bates, who can shape-shift into anyone he touches. Bates takes Eddie's shape and frames him for murder. Later, Bates knocks Barry unconscious and assumes his form, but Thawne realizes the truth and prevents Bates from killing Caitlin and Iris. Bates manages to escape. Caitlin develops a serum to suppress Bates' power, allowing Barry to defeat him and clear Eddie's name. Iris reconciles with Eddie, who reveals his cooperation with the Flash. Bates is locked in the particle accelerator. Meanwhile, Joe and Cisco decide to investigate the car accident scene in Starling City where Wells' wife died. With the help of Captain Quentin Lance, Cisco and Joe locate a buried corpse near the crash site. Cisco also modifies a sonic device for Laurel. Joe advises Quentin to reconcile with her. After a series of tests confirm the corpse is the real Wells, Barry, Caitlin and Cisco locate Thawne's secret room at S.T.A.R. Labs. They find both the Reverse-Flash's costume and the newspaper article from 2024.

Barry talks to Gideon and learns about his battle with the Reverse-Flash in the future, as well as key moments in his life that include marrying Iris, a promotion at the CCPD, and that he created Gideon in the future. With high-tech goggles, the team reawakens Cisco's memories of his alternate-timeline death and the secrets Wells confessed. The team regroups at Joe's house, where Barry reveals his recent time travel and explains his plan to lure Thawne to confess to killing Nora. To trap Thawne, Cisco reverses the polarity of his containment field to protect himself from Thawne, while Caitlin films the interaction to capture Thawne's confession. The trap fails, but Joe shoots Thawne before he can kill Cisco. As Thawne dies, his body transforms, revealing himself to be Bates. Thawne himself calls the team, revealing that he was always aware of their actions because he had them under surveillance. Reverse-Flash goes after Iris and Eddie, but Barry arrives, forcing Thawne to kidnap Eddie instead. Iris finds out about the Flash's identity. Thawne reveals his relation to Eddie. Flashbacks reveal the aftermath of Barry being struck by lightning, and Thawne convincing Joe to let him save Barry's life, and promising to a comatose Barry that he will die.

While looking for Eddie and Eobard, Barry heads to stop a robbery at the gold reserve. When Barry confronts the would-be thief, they are both disoriented by an unknown psychological attack. Back at S.T.A.R. Labs, Iris confronts Barry about being the Flash. He is able to stop the thief, who turns out to be Eiling, whose mind is revealed to be controlled by Grodd. With a lead from Iris, Barry, Joe and Cisco head into the sewers to look for Grodd. The trio realize that Grodd is getting smarter and larger, and during an attack, Joe is kidnapped by Grodd. Cisco and Caitlin build Barry a device that will prevent Grodd's effect. It works, but the device gets damaged in a fight. Barry is able to fight off Grodd's psychic attack and trick him into jumping in front of an on-coming train. Eiling is freed. Iris reveals her feelings for Barry, but states her choice to be with Eddie. Grodd is revealed to be safe and roaming the streets. Meanwhile, Thawne works on a device that will allow him to return to his own time. He reveals to Eddie, Iris and Barry's marriage in the future. Later Thawne completes the device and is revealed to be hiding in a secret chamber inside S.T.A.R. Labs.

Cisco discovers that Eobard has been supercharging his speed through his wheelchair, which is why he is so much faster than Barry. The particle accelerator is activated by Eobard, who has managed to repair it. The team is able to find and rescue Eddie, who ends his relationship with Iris. Worried that the metahumans imprisoned inside the particle accelerator will be killed when it reaches full power, the team plans to relocate them to Oliver's prison on Lian Yu. In order to set up a safe transport, Barry requests Leonard's help. Leonard agrees but only after Barry erases all of Leonard's criminal record. Leonard and Lisa sabotage the transport and allow the metahumans to escape, killing Simmons however. Eobard arrives back at the lab just as the accelerator fully charges. Barry, Firestorm and Oliver all meet outside to fight Reverse-Flash. They coordinate their efforts; Oliver stops him with a nanite injection that disables Eobard's speed and knocks him out. Oliver leaves after informing Barry of an upcoming help request.

Barry visits Thawne in the particle accelerator prison, where Thawne reveals he killed Nora because of hating the Flash, whose future self saved him. Eobard requests Barry to help create a wormhole where Thawne can return to his time, while also allowing Barry to save Nora. Caitlin and Ronnie get married. Eobard tells Cisco that the latter's ability to recall events of alternate timelines was acquired from the particle accelerator explosion. Barry decides to go through with Thawne's offer. The latter states that Barry will have only a short time, or else the wormhole will become a black hole. Barry travels back in time, but his future self signals him not to save Nora. The present Barry returns and stops Thawne from returning to his time. The two fight, while the team shuts down the wormhole. Thawne eventually prevails, but before he can kill Barry, Eddie shoots himself, causing Thawne's existence to cease. The wormhole reappears, and the team is unable to prevent it from becoming a black hole. As the black hole begins to tear the city apart, pulling Eddie inside, Barry speeds into it in an effort to stop it.

This episode aired on October 6, 2015  . Directed by Ralph Hemecker . Recorded 3.58 million views.

Ronnie and Stein turn into Firestorm and destroy the singularity, but at the cost of Ronnie's life. Six months later, while using his speed to repair Central City, Barry operates alone, being the hero and savior of the public and the local government; Cisco works in the police department alongside Joe, and Caitlin works at Mercury Labs. Barry evaluates a crime scene with a victim named Al Rothstein. At a ceremony, the Flash is attacked by Atom-Smasher, whose strength and size manipulation prove too much for Barry, but manages to force his mask off. Underneath the mask Atom-Smasher is revealed to look exactly like Rothstein. Barry is convinced by Joe and the others that he needs help in taking down certain metahumans and Rothstein is defeated by over absorbing radiation. As he dies, Rothstein tells Barry that he was sent to kill him by a person called Zoom. Barry receives a flash memory from Thawne's lawyer containing Thawne's confession to killing Nora. Henry is exonerated and released from prison, and leaves Central City so that Barry can focus on being the Flash. A man arrives at S.T.A.R. Labs and, introducing himself as Jay Garrick, tells the team their world is in danger.

This episode aired on October 13, 2015  . Directed by Jesse Warn . Recorded 3.49 million views.

Jay explains to everyone that he is the Flash on a parallel Earth and that he was in a battle with a demonic speedster named Zoom when the singularity brought him to this Earth without his powers. Stein confirms the claim, describing their world as "Earth-1" and Jay's as "Earth-2". Zoom brings another metahuman from Earth-2 called Sand Demon, later identified as Eddie Slick, to kill the Flash. Cisco analyzes the "sand" left behind and has a vision of the previous fight, frightening him. After Slick kidnaps Officer Patty Spivot, Jay teaches Barry how to hurl lightning. Cisco uses his power to find Patty's location. Barry uses the lightning blast to turn Sand Demon's particles to glass, killing him. Patty reveals to Joe that Mark Mardon killed her father. She joins Joe's metahuman task force. Cisco divulges his ability to Stein, and convinces him not to tell anyone. Stein and Cisco are able to locate 52 breaches with the Earth-2, with the largest one being within S.T.A.R. Labs itself. Joe's estranged wife, Francine, pays him a visit. Stein collapses while talking. On Earth-2 it's revealed that the Harrison Wells of that world is alive and in charge of S.T.A.R. Labs.

This episode aired on October 20, 2015  . Directed by John F. Showalter . Recorded 3.47 million views.

Jay creates a device that stabilizes the singularity and will allow him to return home, but he opts to stay to help Barry stop Zoom. Meanwhile, Lisa Snart shows up asking for Flash's help in rescuing Snart, whom she believes was kidnapped. Barry tracks down Snart, who is revealed not to be kidnapped but is working with his father, Lewis. Lisa states that Snart would never work with Lewis willingly, because the latter was abusive toward her when she was a child. Eventually, the team determines that Lewis placed a bomb inside of Lisa and threatened to kill her if Snart did not help him with his theft. Barry infiltrates Lewis' crew with assistance from Snart. Cisco successfully removes the bomb from Lisa, so Snart uses his cold gun to kill his father in retaliation. Snart is incarcerated in Iron Heights and Lisa leaves. Joe reveals to Iris that Francine is alive and a former addict. Stein turns into Firestorm, but with blue flames. Earth-2's Wells arrives at the lab through the breach.

This episode aired on October 27, 2015  . Directed by Stefan Pleszczynski . Recorded 3.43 million views.

The team is able to temporarily stabilize Stein. Caitlin states that he needs to merge with a new person in order to survive. She identifies two potential candidates: a scientist named Henry Hewitt and a former high school football star named Jefferson Jackson. Hewitt is excited to merge with Stein, but the attempt fails and Hewitt leaves angrily, not knowing that his own metahuman powers have been activated. Jefferson initially refuses, but agrees when Hewitt goes on rampage. After the successful merger, the new Firestorm joins Barry in helping to take down Hewitt, who is incarcerated. Before departing with Jefferson, Stein encourages Cisco to tell the others about his powers. Meanwhile, Francine reveals that she is suffering from a terminal illness and only has months to live. Iris later confronts her for hiding the existence of the former's brother. In the meantime, Wells breaks into Mercury Labs and steals an unknown device. Later, Barry is attacked by a humanoid shark monster sent by Zoom, but is saved by Wells.

This episode aired on November 3, 2015  . Directed by Steve Shill . Recorded 3.87 million views.

Wells, who Cisco nicknames "Harry" to distinguish him from Thawne, reveals that he is responsible for the creation of the metahumans and Zoom on Earth-2. He states that he plans to help Barry's team stop Zoom and other metahumans. At the same time, a metahuman from Earth-2 called Doctor Light arrives and starts robbing banks. Barry recognizes her as the Earth-2 version of Linda. Later, Light attempts to kill Linda and take over her identity, but accidentally kills Linda's boss and is stopped by Barry's team in the process. Harry reveals Cisco's powers to the team, which Cisco uses to locate Light. Barry defeats her with the help of Harry. After locking Light up, they plan to use her to lure Zoom out and defeat him for good. Jay, who dislikes Harry and vice versa, thinks it is too dangerous and leaves the team. Meanwhile, Barry starts dating Patty while Cisco starts a date with a barista named Kendra Saunders. Cisco picks the nickname "Vibe" for himself. Back on Earth-2, it is revealed that Zoom has Harry's daughter captive.

This episode aired on November 10, 2015  . Directed by JJ Makaro . Recorded 3.63 million views.

As the team works to find a way to stop Zoom, Doctor Light escapes from her containment cell. Instead, the Earth-1 Linda agrees to help the team by impersonating Doctor Light. Barry reveals his alter ego to Linda. Harry creates a speed dampening serum and the team stages a fight at one of the breaches in order to trick Zoom through. The attempt fails, as Zoom knew the plan. Instead, he goes after Linda, before fighting Barry. Zoom is much faster and easily overpowers Barry, showing him defeated with his unconscious body to the local news and the police station before ultimately returning to S.T.A.R. Labs. Zoom stabs Barry with his hand, but Cisco shoots him with the serum, which hurts Zoom, but still leaves him with enough speed to escape. Later, Harry reveals that Zoom has his daughter, Jesse, and that he came to Earth-1 to stop Zoom. Barry wakes from his injuries and discovers that he can no longer feel his legs.

This episode aired on November 17, 2015  . Directed by Dermott Downs . Recorded 3.46 million views.

Barry manages to recover from the paralysis, but is unable to use his powers due to the psychological trauma of Zoom exposing Barry's defeat to the city. Iris reaches out to Henry, who returns to help Barry overcome his fears. Wells formulates a plan to close all of the breaches, except one, through which Zoom can enter into the trap set for him. Cisco touches Kendra, but leaves after seeing a winged person in a vibe. Grodd returns, using scientists to steal various chemicals in the hopes of creating more gorillas with his level of intelligence. He later kidnaps Caitlin to help him with his plan. Harry dresses up as the Reverse-Flash in order to trick Grodd into thinking that his "father" is still alive. The plan works long enough for Harry to rescue Caitlin before they both escape. After Barry is fully recovered, they lure Grodd to one of the dimensional breaches and send him to a jungle sanctuary for gorillas that have been experimented on in Earth-2. Later, Cisco meets Kendra again, this time vibing and seeing her as the winged figure.

This episode aired on December 1, 2015  . Directed by Ralph Hemecker . Recorded 3.94 million views.

Vandal Savage arrives in Central City, seeking to kill Kendra. Barry goes to Star City and enlists the help of Oliver and his team to protect her. The team is visited by Malcolm who informs them that Savage is an immortal. Later, Kendra is kidnapped by Hawkman, but Barry and Oliver rescue her and capture Hawkman, who introducing himself as Carter Hall, tells them he and Kendra are soulmates who have been connected for millennia. The pair are destined to die, be reborn, and find each other in each lifetime. Carter also reveals that Savage has killed the pair several times, each time growing stronger. Savage acquires the Staff of Horus, a deadly weapon. Kendra unlocks her abilities and the team decides to regroup in Central City, where Oliver witnesses Samantha Clayton with her son, who is also his. Meanwhile, Caitlin and Harry create a serum that will temporarily increase Barry's speed so that he can defeat Zoom. Jay initially refuses to test the serum, but changes his mind to save Harry when the latter is shot by an unaware Patty, whom Joe later informs about the truth. However, Jay advises against using the serum on Barry. This episode begins a crossover event that concludes on Arrow season 4 episode 8. The two episodes also set up Legends of Tomorrow.

This episode aired on December 8, 2015  . Directed by Kevin Tancharoen . Recorded 3.55 million views.

Mardon breaks James Jesse and Snart out of Iron Heights in an effort to team up to kill the Flash. Snart declines and alerts Barry. Jesse and Mardon place bombs hidden in Christmas gifts throughout the city, threatening to set them off in family homes if Barry does not sacrifice himself. Wells, Cisco, and Jay find one of the bombs and alter its magnetic polarity; they send it into one of the dimensional breaches, which causes it to attract the remaining bombs, removing them from the city. With them gone, Barry subdues Mardon and Jesse, dissuading Patty from killing Mardon. Meanwhile, Iris and Barry tell Joe about the latter's son named Wally, who later shows up at Joe's. Caitlin and Jay start a romantic relationship. Elsewhere, Zoom is revealed to be sending metahumans in order to help Barry get faster so that Zoom can take the latter's speed force, which Harry reluctantly agrees to help Zoom with because of his daughter, Jesse.

This episode aired on January 19, 2016  . Directed by Rob Hardy . Recorded 3.41 million views.

Cisco presents a new idea to slow Zoom down, telling the team about a metahuman, whom he has dubbed the "Turtle", who has the ability to stop the kinetic energy around him and slow everyone to a halt. After Barry fails to stop the Turtle, identified as Russell Glosson, at a diamond unveiling, the team sets a trap at an art exhibit. Barry invites Patty with the intention of telling her his secret, but Glosson is aware of the trap and almost kills Patty before escaping. Later, Glosson kidnaps Patty. The team tracks him down and Barry is able to generate enough speed to move through the kinetic waves to knock him unconscious and save Patty. Patty tells Barry that she is leaving Central City and Harry kills Glosson by extracting a portion of his brain matter. Meanwhile, Joe struggles to develop a relationship with Wally, who has been street racing in an attempt to earn enough money for Francine's medical bills. Caitlin discovers that Jay is dying of an illness caused by Zoom stealing his speed. They vow to stop Zoom to get Jay's speed back in order to cure Jay.

This episode aired on January 26, 2016  . Directed by Michael A. Allowitz . Recorded 3.71 million views.

The team discovers Turtle's death and Jay suspects Harry. Cisco asks Harry for help in controlling his vibing abilities. The latter determines they are connected to Cisco's fear response and triggers a vibe which alerts the team that Eobard Thawne is back. Harry surmises that this version of Thawne is from a point in the future before he went back in time to kill Nora and was protected from being erased. Cisco has a vibe of the future, and the team learns that Thawne is planning to use tachyons to return to his time. Barry arrives and destroys the machine. After a race around the city, Barry stops Thawne and imprisons him at the particle accelerator. However, his capture causes a rupture in the timeline that threatens to kill Cisco, so Barry sends Thawne back to the future to save his friend. Meanwhile, Patty discovers Barry is the Flash but, when he refuses to acknowledge it, she chooses to leave the city. Iris learns that Francine's death is imminent and reconciles with her. Wally takes her advice to do the same.

This episode aired on February 2, 2016  . Directed by Rachel Talalay . Recorded 3.66 million views.

Right before the particle accelerator explosion, Joey Monteleone was thrown into a tar pit and left for dead. Sealed away, he is freed two years later with the ability to turn his body into molten tar. He sets out to get revenge on those who attempted to kill him. Harry creates a device to siphon Barry's speed energy and attaches it to his suit. It steals a portion of Barry's speed. Wells gives the energy to Zoom, who demands the rest. Meanwhile, Wells and Barry also successfully find a way to close the breaches. While going after Joey, Iris is injured when Barry is too slow to save her. Wells tells the team about the device, asking to be returned to Earth-2 and have Barry seal the breaches so Zoom cannot re-enter. After stopping Joey, Barry informs Wells that the team will help the latter to save Jesse. In the meantime, Wally continues racing even after Francine's death.

This episode aired on February 9, 2016  . Directed by Millicent Shelton . Recorded 3.96 million views.

Before heading to Earth-2, Barry closes all but one of the breaches, which is at S.T.A.R. Labs. Using the last breach, Barry, Cisco, and Harry travel to Earth-2, but an energy surge destabilizes the breach and the trio get stuck on Earth-2. Barry decides to impersonate his doppelgänger to get more information on Zoom. He later meets the Iris and Joe of Earth-2 and learns that Iris, who is his doppelgänger's wife, works for the CCPD while Joe is a singer. Barry is attacked by Earth-2's Caitlin and Ronnie, known as Killer Frost and Deathstorm respectively. Joe is killed in the attack. Cisco attempts to help the police stop the pair, but is confronted by his own evil doppelgänger, known as "Reverb" and revealed to have greater powers, including control over nervous systems and manipulation of vibrations. Barry arrives and is stopped by Reverb and Deathstorm. Zoom arrives, kills Reverb and Deathstorm for harming the Flash, and then imprisons Barry. Meanwhile, a new metahuman named Adam Fells appears in Earth-1 Central City. Jay tells Caitlin that he invented Velocity-6, which is the real reason why he lost his speed. Caitlin develops Velocity-7, which Jay uses to engage Fells, who escapes.

This episode aired on February 16, 2016  . Directed by JJ Makaro . Recorded 3.90 million views.

On Earth-2, Zoom issues a demand to Central City to turn in Wells and attacks S.T.A.R. Labs to find Wells and Cisco; but the two escape with Barry-2. The trio updates Iris-2 on what happened with Barry-1. They decide to convince Caitlin-2 to help. After a fight, Caitlin-2 agrees to take the team to Zoom. They arrive and rescue Barry-1 and Jesse, but Zoom shows up too. They are able to escape by the help of Caitlin-2, who keeps Zoom frozen and unable to move, but a third unidentified prisoner, who tries to reveal something about Jay, is left behind. Barry-2 and Iris-2 leave Central City to hide from Zoom. Meanwhile on Earth-1, Caitlin-1 creates "Velocity 9", which Jay uses to stop Adam, who gets incarcerated in Iron Heights. Caitlin-1 discovers that Velocity 9 can cure Jay. The latter, Caitlin, Iris and Joe stabilize the breach and allow Barry-1, Cisco, Harry, and Jesse to return, but Zoom stabs his arm through Jay and pulls him back through the closing breach to Earth-2.

This episode aired on February 23, 2016  . Directed by Hanelle Culpepper . Recorded 3.80 million views.

While everyone tries to move on, the humanoid shark-monster that Harry stopped, known as "King Shark," escapes A.R.G.U.S. custody and heads for Central City to kill the Flash. John Diggle and Lyla Michaels, the new director, arrive to warn Barry. King Shark, later identified as Shay Lamden, shows up at Barry's home looking for the Flash, tracking Barry's electrical field. A.R.G.U.S. arrives and forces Shay to retreat. Later, Barry forces King Shark to chase him out on the water, where Barry creates an electrified underwater cyclone that subdues the latter, and allows A.R.G.U.S. to imprison him again, with Lyla planning to find a cure. Barry vows to open a breach back to Earth-2 to stop Zoom. Meanwhile, Barry and Wally find it hard to develop a relationship. After Caitlin becomes cold due to Jay's death, Cisco becomes scared that she will become Killer Frost; but she assures him that she is only dealing with her grief. Back on Earth-2, it is revealed that, underneath his mask, Zoom looks exactly like Jay.

This episode aired on March 22, 2016  . Directed by Glen Winter . Recorded 3.00 million views.

Barry starts training to get faster so that he can stop Zoom. While out with friends at a club for downtime, Barry and the other club patrons are robbed by an unknown speedster, who then escapes. The speedster turns out to be Eliza Harmon, a Mercury Labs employee who developed Velocity-9 from samples Caitlin gave her to help with Jay's illness. Operating under the alias "Trajectory", Harmon invades S.T.A.R. Labs, imprisons Barry, and demands more V-9. After she threatens Jesse's life, Wells and Caitlin make more of the drug for Harmon, who then speeds off to wreak havoc on the city. Barry manages to stop her before she injects more V-9 into her system. Barry watches as Harmon's speed becomes so intense that her lightning turns blue and she disintegrates. Jesse decides to leave the city to experience the world on her own and stop Wells from doing harmful things just to protect her. Based on what Barry saw from the overuse of V-9, the similarities between Zoom's speed and Jay's sickness, and Cisco's "vibe", the team concludes that Jay is Zoom.

This episode aired on March 29, 2016  . Directed by Alice Troughton . Recorded 3.39 million views.

Barry travels back in time to when Hartley Rathaway attacked the team, and switches places with his past self, in order to have Thawne help him solve the speed force equation. However, after a Time Wraith follows Barry to the past, Thawne deduces Barry's deception. Barry is able to convince Eobard to help him become faster. The wraith comes to the lab, where Caitlin and Cisco are forced to accept help from Hartley to deter the wraith. Afterward, the Barry from the current time arrives, forcing an explanation of the time travel event. Thawne provides the future Barry with the information about the tachyon technology, so that he can return to his time. As Barry prepares to make the jump through time, the Wraith arrives, forcing the past timeline's Barry to intervene, so that his future self can return. Back in his time, Barry is confronted by the Wraith, but a reformed Hartley arrives with his sonic gauntlets and defeats the wraith. Barry gives Iris a footage of Eddie recorded in the alternate timeline, advising her to move on with her life.

This episode aired on April 19, 2016  . Directed by Stefan Pleszczynski . Recorded 3.03 million views.

Years earlier on Earth-2, a young Hunter Zolomon watches as his father murders his mother and is subsequently sent to an orphanage. In the present day, Barry tests the tachyon accelerator (during which he enters and exits a breach to Earth-38 where he meets and befriends one of the heroes of that Earth, Supergirl (as seen in "Worlds Finest"), and is able to enhance his speed four times greater than normal. Barry decides to re-open a breach back to Earth-2, and he believes that Cisco's powers are the key to opening the portals. Meanwhile Caitlin reveals that Jay's Earth-1 doppelgänger is Zolomon and Wells, shocked to hear this, reveals that Earth-2 Zolomon was a convicted serial killer. Zolomon was receiving electroconvulsive therapy during the explosion, and was one of the many affected. With this revelation, the team confirms that "Jay" is Hunter. Cisco opens a breach, and Zoom immediately appears, chasing Barry back to S.T.A.R. Labs. There, Barry uses images of Zolomon's parents as a distraction to trap him, but Hunter escapes, claiming to be "the darkness". Zolomon kidnaps Wally and demands Barry's speed in exchange for Wally's life. Barry agrees, so Wells siphons all of his speed force, leaving Barry powerless. Zolomon injects the speed force into himself, and he kidnaps Caitlin with his enhanced speed before escaping.

This episode aired on April 26, 2016  . Directed by John F. Showalter . Recorded 3.39 million views.

As Barry adjusts to life without his powers, Wells decides to leave the lab to look for Jesse. Shortly after speaking with her, Wells is attacked and kidnapped by Griffin Grey, believing him to be Thawne, who demands that Wells find a cure for his metahuman abilities. Grey has superhuman strength, but is also aging rapidly. Barry discovers that, when Grey uses his super strength, he accelerates the aging process. Barry, Joe, Cisco and Jesse manipulate Grey into exerting his powers until he ages and dies as a weak, old man; his body then reverts back to its 18-year-old self. To fight Zoom, Wells offers to recreate the circumstances that gave Barry his speed. Meanwhile on Earth-2, Zolomon tells Caitlin that he kidnapped her because he is in love with her. Caitlin encounters her doppelgänger, Killer Frost, who was captured by Zolomon as a reminder of Caitlin. Killer Frost convinces Caitlin to help her escape, but then attempts to kill her. Zoom arrives and kills Killer Frost, then warns Caitlin not to free the man in the iron mask. Later, Hunter decides to conquer the other Earths in the multiverse and takes Caitlin with him back to Earth-1.

This episode aired on May 3, 2016  . Directed by Armen V. Kevorkian . Recorded 3.34 million views.

While Barry keeps declining Harrison's offer, the team rigs a hologram of the Flash to stop crime around the city so that no one will know the truth. Henry returns to Central City and joins the team. He argues with Wells on the safety of another explosion. Hunter and Caitlin arrive back on Earth-1 with Hunter declaring the city under his control. Iris confesses her feelings to Barry. The Earth-2 version of Dante Ramon, called "Rupture", arrives on Earth-1 looking to kill Cisco, believing that Cisco killed his Earth-2 brother. Zolomon sends Rupture after the police to send the city a message. Barry and the police stop Rupture, but Zolomon arrives and kills the officers himself, as well as Rupture for failing. He then publicly announces the Flash's disappearance. Cisco and Dante-1 become closer. Barry finally agrees to Harrison's plan. During the process, Barry is seemingly vaporized, while Jesse and Wally are caught in the blast.

This episode aired on May 10, 2016  . Directed by Kevin Smith . Recorded 3.52 million views.

Wally regains consciousness, but Jesse remains in a coma. Cisco has a vibe of Barry and realizes that he is still alive and in the speed force. Barry meets physical manifestations of the speed force in the form of faces familiar to him. The speed force informs Barry that he cannot leave unless he catches a mysterious moving figure, thus gaining his speed back. Cisco and Wells create a path into the speed force so Barry can escape, but the latter chooses to remain so he can earn his powers back. The speed force tells Barry that he cannot become the Flash again until he finally accepts Nora's death. Barry shares a moment with the physical manifestation of Nora, which allows him to finally catch the moving figure himself. With his powers restored and help from Cisco and Iris, Barry returns to S.T.A.R. Labs in time to save the team from the reanimated corpse of Tony Woodward. Afterwards, Barry uses a bit of speed force energy to bring Jesse out of her coma. Across town, Zolomon has assembled an army of metahumans from Earth-2, planning to unleash them on Central City.

This episode aired on May 17, 2016  . Directed by Jesse Warn . Recorded 3.37 million views.

Caitlin returns to the team, but not without emotional trauma from being kidnapped. Zoom's army wreaks havoc across the city. Barry puts out several fires and takes out some of the metahumans to help the police. Back at S.T.A.R. Labs, Barry displays a level of confidence in stopping Zoom that concerns the team and each of them attempts to convince him to be more cautious. Among the attackers is Laurel Lance's doppelgänger, "Black Siren", who attacks various buildings around Central City using sonic blasts. Wally begins taking on metahumans trying to repay the Flash for saving him. The team creates a sonic amplifier tuned to the frequency of Earth-2. They discharge it and render all Earth-2 natives unconscious, allowing Barry to apprehend them all at once, although Zoom survives by escaping to Earth-2. Meanwhile, Cisco begins having vibes of a future Earth-2 being destroyed. Barry convinces Joe to let Wally be a hero. Later, Zoom returns and kidnaps Henry in front of the team. Barry races after them, revealing his identity to Wally, and is forced to watch Zoom kill Henry.

This episode aired on May 24, 2016  . Directed by Antonio Negret . Recorded 3.35 million views.

Zolomon manages to escape Barry by creating a time remnant. After Henry's funeral, Hunter challenges Barry to a race to determine who is faster, threatening to kill everyone Barry loves if he refuses. Harrison discovers Hunter is in possession of a magnetar, a device that will destroy every planet in the Multiverse except Earth-1 which requires both their speeds to power. When an enraged and vengeful Barry refuses to back out, the team locks him in the Pipeline and force Zolomon back to Earth-2 themselves; but Hunter abducts Joe in the process. Wally discovers this and frees Barry, who agrees to Zolomon's race. As Barry races Zolomon around the magnetar, he creates a time remnant of himself who frees Joe and destroys the machine, but at the cost of his life. The "prime" Barry defeats Zolomon, who is then taken away by Time Wraiths for his crimes against the timeline. Barry rescues the man in the iron mask, who is revealed to be the real Jay Garrick, Henry's Earth-3 doppelgänger. Wells and Jesse return to Earth-2 with Jay, who plans to return to Earth-3 from there. Barry, still feeling broken and defeated, travels back in time and stops Thawne from killing Nora.

This episode aired on October 4, 2016  . Directed by Jesse Warn . Recorded 3.17 million views.

After preventing the murder of Nora Allen, Barry returns with Eobard Thawne to the present and imprisons him in a cage that dampens his speed. In the new timeline, which Thawne dubs "Flashpoint", both of Barry's parents are alive; Joe has a poor relationship with Wally and Iris and is chronically in trouble at work; Cisco is a billionaire tech magnate; and Caitlin is a pediatric ophthalmologist. There is also a new Flash in Central City called Kid Flash struggling with his own nemesis, Edward Clariss, known as "The Rival". Barry begins losing his memories of the original timeline due to the new timeline becoming permanent. After discovering Kid Flash is Wally, Barry teams up with him and stops Clariss, but Wally is critically injured in the process. Realizing that the new timeline is worse for those closest to him, Barry is forced to let Thawne return to the past and kill Nora, resetting the timeline and restoring Barry's memories. Back in the present, Barry learns to his horror that the timeline did not reset exactly and Joe and Iris do not talk to each other anymore. Meanwhile, Clariss is confronted by a mysterious voice and finds the message "Alchemy" being scratched into his mirror by an invisible force.

This episode aired on October 11, 2016  . Directed by Ralph Hemecker . Recorded 2.80 million views.

Barry learns of multiple changes to the timeline: Iris has not forgiven Joe for concealing that her mother was alive, Cisco is angry with him for not altering the timeline to save his brother Dante from being killed, and he has a new CSI partner, Julian Albert, who does not like or trust him. Barry decides to travel back to fix the damage, but he is intercepted by Jay Garrick. Jay tells Barry that the timeline never resets exactly and he has to learn to live with his mistakes. Meanwhile, Clariss has visions of "Flashpoint" and locates the person responsible, Alchemy, who restores Clariss' powers and full "Flashpoint" memories. Barry tells the team about the timeline's alterations before confronting Clariss at an abandoned warehouse. Alchemy is there as well, saying that he is preparing for a future event. Cisco arrives and helps Barry defeat Clariss, who is then incarcerated in Iron Heights. The team determines Alchemy is creating other metahumans from "Flashpoint" whom they need to track down. Cisco and Barry reconcile, as do Iris and Joe. Caitlin is secretly revealed to have gained cryokinetic powers. Barry and Iris begin dating, while Clariss is confronted by the voice of Alchemy for his failure before being killed inside his cell by an unidentified metallic being.

This episode aired on October 18, 2016  . Directed by Armen V. Kevorkian . Recorded 2.67 million views.

Wells and Jesse return to Earth-1, where she reveals she has gained super speed from the second dark matter blast. Wells hopes everyone will dissuade her from using her powers. Elsewhere, foster child Frankie Kane develops metahuman magnetic powers that manifest as an alternate personality, Magenta, who attacks her abusive foster father. Julian confronts Frankie at the station and is nearly killed by Magenta. Barry learns from Magenta that she got her powers from Alchemy. She escapes and later goes to the Central City Hospital to kill her foster father by dropping an oil tanker on the building. Barry creates a vortex to hold the tanker in place, but is unable to confront Magenta simultaneously. Wells sends Jesse to help. She takes over the vortex while Barry talks Kane into gaining control over Magenta. Wally, grappling with disappointment over having no speed, realizes he is having the same dreams from "Flashpoint" that Kane describes. Wells tells Jesse that he will support her decision and presents her with her own speedster costume. Joe later shows Barry and Julian footage of Clariss being killed in his cell by an unseen force, manifesting only as a flying ball of white light.

This episode aired on October 25, 2016  . Directed by Stefan Pleszczynski . Recorded 2.80 million views.

Three years ago, Sam Scudder and Rosalind Dillon, former cohorts of Leonard Snart, were caught in the original particle accelerator explosion. In the present, Barry begins training Jesse on how to use her powers. Wells suggests the team locate a doppelgänger of his from another Earth to replace him on the team once he and Jesse leave. Scudder returns from being trapped in a mirror-like dimension with the ability to transport himself and others through reflective surfaces. He reunites with Dillon, who now has vertigo-inducing powers, and they go on a crime spree. Barry and Jesse (as "Jesse Quick") confront them, but are defeated after Barry ends up trapped inside a mirror by Scudder. Caitlin secretly uses her emerging ice powers to help Barry free himself from his predicament. He and Jesse then successfully capture Scudder and Dillon. After evaluating the candidates, the team recruits the friendly and eccentric Wells of Earth-19, despite the Earth-2 Wells' misgivings. Jesse and her father then return to Earth-2, but not before Wells apprises Cisco of Barry's suspicious escape. That night, Caitlin accidentally freezes the water in her shower and her appearance begins showing signs of her Earth-2 doppelgänger, Killer Frost.

This episode aired on November 1, 2016  . Directed by C. Kim Miles . Recorded 2.77 million views.

Without informing the others, Caitlin visits her estranged mother, Carla, at her medical research company to have her powers examined, but leaves after viciously attacking another scientist who intended to exploit her condition. Meanwhile, a gigantic creature repeatedly appears and disappears on the streets of Central City. Cisco grows suspicious of the newly-recruited "H.R." Wells when he does not provide much help in battling the monster. The monster is revealed to be simply a hologram operated by a bullied 15-year-old boy wanting to create fear in others. Barry exposes the deception in time to keep police snipers from harming civilians and prevents Julian from shooting the boy, whom he mistakes for a metahuman. H.R. is revealed to have no technical knowledge at all. He admits that he is only an "idea man" for his tech company on Earth-19 and that he came to Earth-1 primarily to get material for a novel. The team decides to give him a chance to prove his worth as an assistant. A badly shaken Julian reconciles his differences with Barry. Carla informs Caitlin that her powers are increasing and that she needs to stop using them or her condition will become irreversible.

This episode aired on November 15, 2016  . Directed by JJ Makaro . Recorded 3.01 million views.

When Wally relates his recent dreams of being Kid Flash, Barry reveals what happened to him during "Flashpoint." A metahuman H.R. nicknames "Shade" appears and murders a stockbroker. Caitlin reveals her powers to Cisco and has him "vibe" her to learn her future. Cisco sees himself fighting Killer Frost, causing Caitlin to contemplate leaving for good. Alchemy summons Wally to him, so the team locks Wally in the particle accelerator for his own safety. Meanwhile, Barry and the others stop Shade's next attack and capture him. Cisco tells everyone the truth about Caitlin and Barry privately confesses to her that her powers are a result of "Flashpoint." Wally volunteers to lead the team to Alchemy to capture the villain and stop the memories, which are causing him pain. Barry, Joe, and a S.W.A.T. team locate Alchemy and his followers and surround them. The metallic being that killed Clariss appears and attacks them, revealing himself to be a speedster that only Barry can see. As Barry fights their attacker, Alchemy entices Wally to pick up his fallen energy weapon, which encases Wally in a crystal cocoon. Calling himself "Savitar", the speedster overpowers Barry and prepares to stab him with a blade from his arm.

This episode aired on November 22, 2016  . Directed by Kevin Smith . Recorded 2.95 million views.

Savitar opts to drag Barry across the city, while battering him to demonstrate his superiority. Cisco and Caitlin arrive to rescue Barry and Savitar flees. Caitlin, with her Killer Frost persona having taken over, violently interrogates one of Alchemy's followers at CCPD headquarters. When Julian catches her, she coerces him to find the other acolytes so they can lead her to Alchemy, who can presumably remove her powers. Barry and Cisco track her down and imprison her, but the team is fractured after she reveals Barry's role in Dante's death by creating "Flashpoint." Greatly concerned and disregarding the consequences, Joe breaks Wally out of the cocoon. Wally emerges with unmanageable speed powers and he races away in a confused state. Barry offers his life to Caitlin for her freedom in a successful attempt to restore her sanity and gain her help in treating Wally. Joe and Barry locate Wally, stabilizing his condition with Caitlin's serum, and Wally soon embraces his new abilities. Julian agrees to protect Caitlin from the police, but forces Barry to resign from the CCPD in exchange, believing him morally unfit for wanting Caitlin shielded. Julian is later revealed to be Alchemy and working for Savitar.

This episode aired on November 29, 2016  . Directed by Dermott Downs . Recorded 4.15 million views.

Barry investigates a meteor crash outside Central City that turns out to be a spaceship from which aliens emerge. Lyla tells the team that the "Dominators" landed previously in the 1950s, but then mysteriously departed. Needing help, Barry assembles the original Team Arrow, Thea, the Legends, and Supergirl. The team begins training at a S.T.A.R. Labs facility, sparring against Supergirl to prepare for combat against the aliens. Cisco reveals a message to Rip Hunter from Barry's future self, which exposes Barry's manipulation of the timeline and how it affected other team members. Oliver, Supergirl, Felicity, Martin, and Jefferson are left as the only ones who still trust Barry. The Dominators abduct the President. Supergirl leads most of the others in a rescue effort, but the Dominators kill the President and ensnare everyone with a mind control device. The controlled heroes return and attack S.T.A.R. Labs. While Oliver holds them off, Barry lures Supergirl to the device and manipulates her into destroying it, freeing everyone. The team decides to trust Barry again. Suddenly, Sara, Ray, Diggle, Thea, and Oliver are teleported away before Barry can intervene. This episode begins a crossover event that continues on Arrow season 5 episode 8, and concludes on Legends of Tomorrow season 2 episode 7.

This episode aired on December 6, 2016  . Directed by Rachel Talalay . Recorded 3.14 million views.

Barry asks Jay Garrick for help against Savitar. The two heroes locate and defeat Alchemy and return his weapon to its box, causing Savitar to disappear before he can kill Jay. Discovering Julian to be Alchemy, Barry reveals his own identity to him to get further information. Julian relates how he located the Philosopher's Stone following a vision of his dead sister and that he has been having blackouts ever since. Savitar manifests through Cisco using visions of Dante and fights Barry and Wally, but Caitlin manages to convince Cisco to close the box again. The team communicates with Savitar through Julian, who claims that Barry, in the future, will imprison him. He also says that one teammate will betray them, one will fall, and a third will suffer a fate worse than death. Trying to end Savitar's threat, Barry and Jay throw the box into the speed force but, in the process, Barry is thrown five months into the future and witnesses Savitar killing Iris. Jay tells Barry that the future is not fixed. Wally is given his own "Kid Flash" costume, Julian gets Barry's job back for him, and Barry rents a new apartment for himself and Iris.

This episode aired on January 24, 2017  . Directed by Millicent Shelton . Recorded 2.72 million views.

Barry has been having nightmares about Iris's murder. Jared Morillo attempts a robbery, but is confronted by Barry, who recalls a news report during his visit in the future when Barry captures Plunder. The distraction allows Morillo to overpower Barry and escape. H.R. launches the museum, but no one visits it. In a second confrontation, Wally intervenes and captures Morillo, gaining praise by everyone except Barry. He eventually reveals the future he saw to everyone but Joe. The team decides to change the course of other events in order to prevent Iris's death. Using Cisco, Barry accesses the future memory, in which the news reveal that the S.T.A.R. Labs museum will close and Caitlin will become Killer Frost. Morillo escapes, and Barry decides to change the first event by letting Wally capture him. Cisco relaunches the museum, starting with an exhibition for elementary school students. Julian is persuaded by Caitlin to join the team. A mysterious woman from another Earth arrives, searching for H.R.

This episode aired on January 31, 2017  . Directed by Harry Jierjian . Recorded 3.06 million views.

An Earth-19 bounty hunter named Gypsy, possessing powers similar to Cisco's, arrives on Earth-1 intending to take H.R. back to Earth-19 for trial and execution, as inter-dimensional travel is forbidden there. Cisco demands a trial by combat for H.R.'s life, which she accepts. As the duel is to the death, Barry and H.R. try to ambush Gypsy to save Cisco, but she easily defeats them. Meanwhile, determined to leave a legacy, Iris persuades Wally to help her bust an arms dealer. While he is out scouting, she confronts the dealer, seemingly unafraid of death. Wally manages to save her. Julian discovers a flaw in Gypsy's fighting style. Cisco exploits this weakness during their battle, which allows him to defeat her. Cisco spares Gypsy's life, but she makes it clear that H.R. can never return to Earth-19, since she will state that she killed him. Joe gets angry with Iris and is suspicious of her lack of fear. Barry plots to have Wally increase his speed so that Wally can save Iris from Savitar.

This episode aired on February 7, 2017  . Directed by Rob Hardy . Recorded 2.91 million views.

Barry and Wally continue their training in order to save Iris from Savitar. They race against each other, and Barry wins by phasing through a building. Julian finds a decayed corpse that was murdered just eight hours ago. He informs Joe that this is surely the work of a metahuman. The body is taken to S.T.A.R. Labs for investigation, where Caitlin and Julian observe it turning to ash. Iris confesses to Barry that she is afraid of her future. The meta responsible for the disintegrated corpse attacks Joe and is revealed to be targeting the police who arrested him in Flashpoint. The metahuman tries to disintegrate a bridge on the train Joe is on, forcing Barry to phase the train through the wreckage of the bridge. Barry teaches Wally how to phase, which Wally uses to expose the meta to his blood and strip him of his powers. Joe insists that everyone be honest with him from now on after learning of Iris's future death. While practicing phasing, Wally is shocked to see Jesse coming through a portal. Jesse says her father has been abducted by Grodd and taken to Gorilla City.

This episode aired on February 21, 2017  . Directed by Dermott Daniel Downs . Recorded 2.78 million views.

Earth-2 Wells is captured while running through the woods. Jesse explains that he was leading an expedition to Gorilla City that was ambushed and killed while Wells disappeared. Barry recalls that in the future Central City will be attacked by gorillas. He, Julian, Cisco, and Caitlin go to rescue him but are captured by Grodd. Speaking through Wells, Grodd asks Barry to help him usurp his master Solovar. Barry agrees to fight Solovar in the arena for the lives of the others and wins, but refuses to kill him. Grodd seizes control of Gorilla City and prepares an invasion of Earth-1. Cisco asks Caitlin to kill him so Grodd cannot open a portal, but she refuses. Barry fakes his death and Grodd removes him from his cage. He resuscitates himself and frees the others, and they return to Earth-1. Jesse and her father reunite and Wally and Jesse recommit to their relationship. Julian asks Caitlin out on a date. Grodd assembles his army with a brainwashed Gypsy at his side.

This episode aired on February 28, 2017  . Directed by Dermott Daniel Downs . Recorded 2.87 million views.

Harry and H.R. clash over their different personalities. Jesse informs her father that she intends to stay on Earth-1 with Wally, which Harry initially tries to prevent. Harry subdues Gypsy when she ambushes Cisco and Barry, and the team realizes that Grodd and his forces have reached Central City. Using his powers, Cisco determines that the gorillas will attack the center of town. This turns out to be a distraction for Grodd to abduct a visiting Army general. Barry contemplates killing Grodd as the only way to permanently stop him and also change the future, but Harry encourages him to find another way. Taking control of the general, Grodd attempts a nuclear missile strike on the city. Barry prevents the attack, so Grodd and his gorilla army invade the city themselves. Cisco travels to Earth-19 to ask Gypsy for help. The speedsters distract the soldiers while Cisco and Gypsy bring Solovar to Earth-1, who defeats Grodd and assumes leadership once again. All the gorillas return to Earth-2, with the exception of Grodd, who is turned over to A.R.G.U.S. Gypsy kisses Cisco before telling him he could not handle her, then returns to Earth-19. Barry proposes to Iris. While going out to pick up dinner for Jesse, Wally is confronted by Savitar.

This episode aired on March 7, 2017  . Directed by Alexandra La Roche . Recorded 2.52 million views.

Wally continues having visions of Savitar and, after a physical altercation with him, finally admits this to the team. The team attempts to question Savitar via Julian, who again acts as a conduit. Savitar casts doubt on whether the Philosopher's Stone is truly lost to the speed force. Caitlin confesses that she kept part of the Philosopher's Stone, hoping to use it to remove her powers. Barry and the team figure out that Savitar is trapped inside the speed force but Wally is at home with Jesse when they realize this. Wally, after being confronted by Savitar who appears as a vision of his mother, steals the stone fragment from the lab, creates a portal, and launches the fragment into the speed force, believing this will exile Savitar for good. Barry arrives just as the portal draws Wally into it, trapping him in the speed force. Savitar, having successfully manipulated Wally, emerges from the speed force and fights Barry, taunting him by boasting he will not kill him before Barry watches Iris die before his eyes. Barry breaks off Savitar's arm blade using his vibrating hand, causing Savitar to retreat.

This episode aired on March 14, 2017  . Directed by Gregory Smith . Recorded 2.39 million views.

Feeling responsible for everything bad that is happening, and that Wally is suffering inside the speed force, Barry decides to rescue him. Cisco vibes Barry into the speed force, where he encounters manifestations of friends and foes who had previously sacrificed their lives. Less accommodating than before, they push Barry to understand true sacrifice and that he must be the one to save Iris in the future. Barry is also confronted by his former enemy, Hunter Zolomon, and defeats him. Jay Garrick, having been contacted by Cisco, joins Barry inside the speed force and voluntarily takes Wally's place so Barry and Wally can escape. Meanwhile, Jesse uses the armor shard to locate and face Savitar by herself, managing to wound the villain with it before he escapes. Later, Jesse decides to go to Earth-3 to protect it until the team can free Jay from the speed force. Barry admits to Iris that even though he does love her, he proposed for the wrong reasons and suggests they take some time apart from one another.

This episode aired on March 21, 2017  . Directed by Dermott Daniel Downs . Recorded 2.71 million views.

J'onn J'onzz and Mon-El arrive on Earth-1 with a comatose Kara. The Music Meister attacks and places Barry in a similar coma. He wakes up in a musical world and finds Kara. Meister tells them that if they follow the script, they will return to the real world. Barry and Kara are forced to work as singers in a nightclub run by Malcolm, with Winn working as a piano player, Cisco as a waiter and Stein and Joe as two gangsters opposing Malcolm. Barry and Kara find Malcolm's son, Mon-El, and Stein's and Joe's daughter, Iris, in a forbidden relationship. Kara and Barry convince the pair to reveal their love, also helping Barry and Kara to realize their own mistakes. Malcolm, Stein and Joe subsequently decide to go to war. Barry and Kara are shot in the crossfire, but the real Cisco, Mon-El and Iris vibe into their world to save them, allowing Barry and Kara to admit their loves for Iris and Mon-El. They wake up in S.T.A.R. Labs, and Meister reveals that he just wanted them to realize their love. Kara's team returns to Earth-38, and Barry and Iris move back in together. Barry re-proposes to Iris, who accepts. This episode is a crossover with Supergirl.

This episode aired on March 28, 2017  . Directed by Nina Lopez-Corrado . Recorded 2.39 million views.

Abra Kadabra, a criminal from the 64th century, comes to Central City, stealing from numerous tech companies and killing two guards. Gypsy returns, in pursuit of Kadabra, to avenge her partner. Kadabra offers the team the identity of Savitar in exchange for his freedom. Against Gypsy's wishes, a desperate Joe releases Kadabra, who escapes to Thawne's time vault after Gypsy fails to stop him and retrieves a power source. Kadabra also triggers an explosion that critically injures Caitlin. Refusing to take off the necklace suppressing her powers, even though doing so could save her life, Caitlin asks Julian to perform surgery with her guidance instead. Kadabra attempts to return to his own time, having used the stolen technology to build his own time machine, but he is foiled by the team with Gypsy's help. Barry decides that the only way to save Iris' life is by traveling to the future. Later, a still-recovering Caitlin loses consciousness and begins convulsing, before her vital signs flatline. A distraught Julian rips the necklace from her neck and her vital signs return to normal, as her injuries heal rapidly. She awakens, but in the guise of Killer Frost, and starts attacking the group with her ice powers.

This episode aired on April 25, 2017  . Directed by Tom Cavanagh . Recorded 2.67 million views.

Killer Frost destroys the necklace. Barry travels to 2024, when he learns that Cisco lost his powers after Killer Frost shattered his hands and forced him to use mechanical prosthetics, H.R. has become a successful novelist, Julian works at Iron Heights tending to Killer Frost, Wally is catatonic with a shattered spine, Joe is depressed, and future Barry is a recluse hiding at S.T.A.R. Labs. In his absence, Top and Mirror Master have taken over Central City. Barry fails to learn Savitar's identity. Cisco secretly uses a device to prevent Barry from returning to the past, hoping he will put things right. Barry rounds up Julian, Joe, and H.R., reuniting Team Flash. Top and Mirror Master overwhelm Barry with their powers but, after overhearing him, future Barry uses Cisco's device to negate the villains' abilities, helping to defeat them. Future Barry gives Barry information and tells him to find a physicist named Tracy Brand, who developed a speed force-based trap years after Iris' death. In the present, Killer Frost meets with Savitar. She is reluctant to trust him, but changes her mind when Savitar's armor opens up and he steps out, revealing his identity to her.

This episode aired on May 2, 2017  . Directed by Hanelle Culpepper . Recorded 2.69 million views.

Barry, Cisco, and H.R. visit Tracy to seek her help in making a trap for Savitar; they are interrupted by Killer Frost, who attempts to kill Tracy, but is defeated before she escapes. Tracy goes to S.T.A.R. Labs with Team Flash and is shown her future. Killer Frost later decides to kidnap Joe's girlfriend, Cecile, and demand Tracy in exchange. Killer Frost's plan fails, leading to a battle between her and Cisco. Defeated, she is whisked away by Savitar, but not before Cisco draws some of her blood in order to potentially make a cure for her powers. Meanwhile, Joe admits his love to Cecile and tells her about Barry and Wally's alter egos. H.R. develops feelings for Tracy. Later, Tracy, inspired by the events, plans to build a trap for Savitar, while Barry has a revelation regarding Savitar's identity, given how much Savitar knows about everyone, and confronts him outside the city. Savitar confirms Barry's new assumption and reveals himself to be a future version of Barry Allen.

This episode aired on May 9, 2017  . Directed by David McWhirter . Recorded 2.71 million views.

Future Barry explains to his younger self that he is a time remnant, created by his future self while fighting Savitar. After being shunned by Team Flash, future Barry became depressed and ran back in time to ultimately become Savitar. He explains that he needs to kill Iris so that Barry will be forced to create him in the future. Cisco proposes they stop Savitar from remembering any of their strategies by stopping Barry from creating new memories, but miscalculations cause Barry to lose his memory. Savitar also loses all of his memories, resulting in Wally's powers disappearing, since Savitar never gave them to him. A pyromaniac named Lucious Coolidge gets released because of Barry's inability to testify correctly. Killer Frost helps Cisco and Julian develop a way for Barry to regain his memories so that Savitar can, as well. When Coolidge starts a fire, Iris helps Barry regain his memories in time to stop the fire with assistance from Wally. Tracy and H.R. develop a romance. She then shows the team the completed speed force trap, which requires a high amount of energy. The final scene cuts to a room that has an alien power source, as well as King Shark.

This episode aired on May 16, 2017  . Directed by Michael Allowitz . Recorded 2.48 million views.

With 24 hours left before Iris dies, Team Flash learns that there is only one energy source that can power the "Speed Force Bazooka" in the form of a salvaged Dominator technology held at an A.R.G.U.S. facility. Barry and Cisco ask Lyla for it, but she refuses because of her mistrust of Barry due to his creation of Flashpoint. Barry then visits Snart in 1892, when he was travelling with the Legends, and recruits him to help Barry break into A.R.G.U.S. and steal the device. In the process, A.R.G.U.S. agents eventually capture Barry and Snart, but Lyla, seeing the kindness in Barry's actions, allows Barry to take the device. Snart advises Barry to use the goodness in him to defeat Savitar. Tracy decides to join the team. Cisco vibes about his battle with Killer Frost and leaves to fight her. Joe tries to hide Iris from Savitar on Earth-2 with Harry but future Barry tricks H.R. into revealing up her location by pretending to be his younger self, breaks Wally's leg and kidnaps Iris in front of a horrified Joe. Flash uses the "Speed Force Bazooka" on Savitar, but it fails when Savitar counteracts it with the Philosopher's Stone, which is made out of calcified speed force energy. Savitar then stabs Iris in the back in front of Flash seemingly killing her as he escapes.

This episode aired on May 23, 2017  . Directed by David McWhirter . Recorded 3.04 million views.

H.R. reveals he swapped places with Iris and dies from his injuries. Realizing Iris is not dead, Savitar kidnaps Cisco and forces him to modify the Bazooka into an "inter-dimensional quantum splicer". This will allow Savitar to disperse himself throughout time and protect him from the paradox that threatens to erase him. Barry meets with Savitar, believing he can be redeemed and they go to S.T.A.R. Labs. Although Barry and Iris try to get through to him, Savitar wrecks the lab and orders Caitlin to kill Cisco, but Gypsy saves him. Savitar and Killer Frost open a portal into the Speed Force. The Black Flash intervenes, but is frozen and destroyed by Caitlin. Savitar then attempts to execute his plan. However, Cisco modified the Bazooka into a 'skeleton key' which frees Jay from the Speed Force prison. Barry, Wally and Jay engage Savitar, while Cisco, with Gypsy's help, convinces Caitlin to abandon Savitar. Barry phases through and destroys Savitar's armor before Savitar is killed by Iris, saving Barry, and erased from existence. As Team Flash mourns H.R., Caitlin decides not to use Julian's cure, leaving the team so she may find her own purpose. Later on, an energy storm appears over Central City, caused by the Speed Force prison being empty. Barry explains that he needs to atone for creating Flashpoint and enters the prison, entrusting Central City to Iris and the team.

Iris has been aiding Team Flash in Central City for six months, but refuses to grieve Barry. A flying samurai with superpowers appears in Central City, threatening to destroy the city if the real Flash does not face him. Cisco reveals he has formulated a way to bring back Barry without destabilizing the Speed Force and tracks down Caitlin for help, but is forbidden by Iris to bring Barry back. Against Iris' orders, Team Flash successfully returns Barry, who rambles random statements and continually writes symbols on the walls. Wally engages the samurai, but is defeated. Cisco deciphers Barry's writings and finds an apparently meaningless sentence. In an attempt to recover Barry's memories, Iris gives herself up to the samurai. The plan works and Barry speeds away, rescuing Iris and defeating the samurai, who is revealed to be an android. Caitlin rejoins Team Flash, but is revealed to have been working for a mobster called Amunet, while also continuing to prevent the Killer Frost personality from emerging. The "Samuroid" is revealed to have been controlled by a supremely intelligent man in a superpowered wheelchair, whose plan was to draw out the Flash for his next schemes.

When Barry, Joe, and Cisco report to a crime scene, they discover remnants of a mysterious code. Cisco presents Barry with a technologically advanced suit, intended to facilitate his activities. He tests it out, trying to save someone from a haywire car controlled by metahuman Ramsey Deacon. Gypsy arrives on Earth-1 for a date with Cisco, who is forced to cancel it so as to focus on Deacon. Acting on a suggestion from Caitlin, Iris signs her and Barry up for couples therapy to sort out their relationship. Deacon kidnaps a witness, a former member of a tech team that stole his idea for profit. Barry and Wally go to save him, but Deacon uses his abilities to send Barry's suit haywire. On Iris' instruction, Barry throws lightning at himself, shorting out his suit. He then incapacitates Deacon, who is locked up in the meta wing of Iron Heights, revealed to be part of the Thinker's plan. Cisco finally goes out with Gypsy. Wondering how Deacon gained his powers being absent during the particle accelerator incident, Barry and Joe learn from Deacon that there are "others."

In flashbacks, the Thinker observes Becky Sharpe, a woman with seemingly unending bad luck, and determines that she will be easily manipulated. In the present, Becky robs a bank and gets away when Barry slips on marbles. Harry arrives from Earth-2 and tells Wally that Jesse has decided to break up with him in order to focus on her vigilantism. Cisco deduces that Becky is a metahuman with the power of favorable luck while inducing misfortune to others. Barry realizes that the portal he used to escape the Speed Force exposed an entire busload of people, including Becky and Deacon, to transformative dark matter. Harry informs Cisco that Jesse has expelled him from her crime-fighting team due to his attitude. Becky's powers expand out of control, reactivating the particle accelerator, which Harry deliberately allows, nullifying Becky's powers and leading to her incarceration. Cisco and Harry identify twelve new metahumans created on the bus and the latter suspects that an unknown party has manipulated the events surrounding Barry's return. Wally decides to leave on a journey to find himself. The Thinker is revealed to be spying on S.T.A.R. Labs through the "Samuroid" helmet. Joe learns Cecile is pregnant.

Gypsy's father, Breacher, attacks Cisco, vowing to hunt and kill him in 24 hours, but allowing the romance should he survive. Team Flash learns that the bus driver was murdered and tracks down another passenger, Ralph Dibny, a former corrupt CCPD detective who Barry exposed that is now a private investigator. As two thugs attack Dibny, he is revealed to have the power to stretch. Caitlin stabilizes his powers with a serum. The team learns that Ralph has been blackmailing Mayor Bellows over his adultery, so the latter hired the thugs. Barry confronts Ralph for his actions, but Ralph maintains he was a "good cop." He later stops blackmailing Bellows, who still attempts to kill him while Breacher mistakes the former for a Plastoid, the species that invaded Earth-19 previously, and attacks him. Cisco intervenes and saves Ralph, whom Barry, having revealed his alter-ego, convinces to help arrest an escaping Bellows. Admiring Cisco's gallantry, Breacher allows the relationship. Barry recruits Ralph for Team Flash and learns that someone named DeVoe instructed Ralph to watch Bellows. Barry remembers that Abra Kadabra and Savitar both mentioned a DeVoe. Meanwhile, Caitlin finds a message on her apartment door.

While failing to track DeVoe, Team Flash is visited by Felicity, who joins Iris' bachelorette party. Mocking Cisco's plans for Barry's bachelor party, Ralph takes the men to a strip club, where they find Cecile's daughter, Joanie, working. Joe confronts her, but she states that she is only doing feminist research. Ralph incites a brawl, leading to the men's arrest until Harry posts bail. Meanwhile, Amunet's enforcer, Norvock, demands Caitlin's return and attacks the women when she refuses. Killer Frost emerges and repels him, later telling Iris that Caitlin accepted Amunet's employment in exchange for the means to control Frost. Learning that Amunet is holding a metahuman she calls the "Weeper," whose tears are a strong narcotic, prisoner and intends to sell him, Iris' party decides to stop her. Though Caitlin refuses to join, she attacks Amunet when seeing her friends in danger. Using a strong magnet, the team robs Amunet of her metal shards, leaving her powerless. Iris dissuades Frost from killing Amunet, who promises revenge. Both parties refuse to tell each other about their adventures. Iris asks Caitlin to be her maid of honor while Joe convinces Joanie to tell Cecile about her research. DeVoe captures the Weeper.

Barry trains Ralph to use his abilities, with Cisco making a stretchable suit for him. Another bus metahuman, a Lakota Sioux Native named Mina Chayton who can animate statues, starts attacking Central City & stealing pieces of a Black Bison necklace, which she claims belongs to her tribe. When Barry and Ralph catch up to her, she attacks Barry with a caveman statue and attempts a getaway. Ralph chooses to stop her, but a little girl is injured in the process. Ralph regrets his actions, but is comforted by Barry. Chayton escapes CCPD, going after the last necklace piece held at the museum. When Barry and Ralph confront her, she brings a dinosaur skeleton to life. Barry arrests Chayton while Ralph saves a security guard from the skeleton. Later, Ralph reveals he mailed the necklace back to Chayton's tribe before visiting the little girl in the hospital, using his abilities to entertain her. Meanwhile, Harry, trying to make friends, works with his doppelgangers from alternate Earths, dubbed The Council of Wells. They figure out that DeVoe is a man named Clifford DeVoe. Barry and Joe head to DeVoe's house, but find a middle-aged man in a wheelchair.

Barry and Joe interrogate DeVoe and his wife to try and get more information. In flashbacks, DeVoe and his wife build a thinking cap to improve his brain capacity, powering it through the particle accelerator explosion. DeVoe's increased brain power accelerates his amyotrophic lateral sclerosis, forcing his wife to build him a special chair to keep him alive. Barry discovers the camera in the Samuroid head and goes to DeVoe's house, narrowly avoiding being caught by DeVoe's wife. Barry later confronts DeVoe, who reveals his true identity, leading to Cisco dubbing him "The Thinker." Wally returns to Team Flash from Blue Valley.

Barry, Oliver, Sara, Alex, Martin and Jax wake up in a Nazi concentration camp on Earth-X wearing power dampeners. The arriving SS Sturmbannführer is revealed to be the Earth-X doppelgänger of Quentin Lance, who plans to execute them, but they are saved by Citizen Cold (the Earth-X doppelgänger of Leonard Snart) and Ray Terrill. Snart and Terrill take them to the headquarters of the Freedom Fighters, where the team meets the resistance movement's leader, General Schott (Winn Schott's Earth-X doppelgänger). They learn that the only way back to Earth-1 is through a temporal gateway in a research facility, which Schott plans to blow up to strand Dark Arrow (Oliver's Earth-X doppelgänger) on Earth-1. Oliver disguises himself as Dark Arrow to infiltrate the facility and discovers the Nazis have an ace in the hole, a militarized timeship called Wellenreiter. Barry and Ray battle the Freedom Fighters' Red Tornado to stop it from destroying the gateway while the rest of the team enter the facility to reactivate its portal. During the battle, Stein is shot and gravely wounded. On Earth-1, Eobard Thawne prepares to perform surgery on Kara to save Overgirl. Felicity and Iris try to stop him, but are captured. This episode continues a crossover event that begins on Supergirl season 3 episode 8 and Arrow season 6 episode 8, and concludes on Legends of Tomorrow season 3 episode 8.

While out Christmas shopping, Barry is ambushed and kidnapped by DeVoe while Caitlin is kidnapped from Jitters by Amunet. Iris claims they have to look for both of them, despite Harry's claim that they have insufficient time and resources and that they can only afford to search for one. Barry is held in DeVoe's lair. Caitlin is forced by Amunet to perform surgery on a metahuman named Dominic Lanse who can read minds. They try to escape, but Amunet blocks their exit. Caitlin manages to briefly incapacitate Amunet, so she and Dominic can flee the building in which they are being held. Once outside, they are rescued by Cisco and Ralph, as Iris chose to focus on finding Caitlin. Barry manages to escape from DeVoe. Team Flash celebrates Christmas at the West house and Dominic joins them. Barry gets a security alert from his apartment. When he arrives, he receives a phone call from Dominic, who reveals that Amunet re-kidnapped Dominic and DeVoe transferred his consciousness into Dominic's body. Barry discovers DeVoe's original body dead on his apartment floor and realizes DeVoe has framed him for his "murder;" the police arrive and Barry lets himself get arrested, not wanting to leave Iris again.

Barry stands trial for the murder of Clifford DeVoe, with Cecile representing him. Cisco and Joe have to leave during the trial for a meta investigation, in which a meta caused people to collapse. Singh reveals to Joe he is appearing as a witness for the prosecution against Barry. The meta is eventually discovered as Neil Borman, who is a meta who produces radiation, which is causing the illness and collapsing. Barry takes him on, but is ill equipped to deal with the situation. Cisco and Killer Frost travel to the scene where Caitlin tries to freeze Borman, who quickly defrosts and incapacitates Caitlin. Barry creates a vacuum seal around Borman to contain the radiation, with Cisco transporting the radiation to the dead Earth-15, draining the meta and defeating him. Barry is eventually found guilty by the jury and is sentenced to life in prison.

Barry uses his speed to secretly help the guards contain the other inmates during a prison riot. He also befriends Dave Ratchet, his father's former cellmate. The next day, Barry meets Axel Walker who was later broken out of prison by his mother Zoey Clark, his father's one-time partner Prank. Axel challenges Ralph by threatening to cause chaos in the city. Ralph attempts to stop him but is wounded by Axel and is evacuated by Cisco. Ralph sneaks into the prison to talk to Barry about how scared he is. Barry reassures him that being a hero isn't about not being scared, but about having the ability to rise above your fear. Cisco and Caitlin go to rescue the hostages, but get captured by Axel and Zoey, who intend to kill them. Ralph arrives, and attempts to shield the two from an acid shower, until Wells manages to hack into the shower system to neutralize its acidity. Iris visits Barry in prison, where they reaffirm their love for each other. Ralph and Cisco go to get coffee, where they meet the excitable girl from the wedding. The girl writes in her journal, where she appears to be writing in the language Barry was using when he came out of the Speed Force.

Cecile develops telepathic abilities as a result of her pregnancy, combined with dormant dark matter in her cells, which Caitlin assures her should be temporary. In prison, Barry learns that Ratchet is innocent of a robbery-homicide that was actually committed by Sylbert Rundine fifteen years prior. Barry asks the team to look into the case. Rundine turns out to be a bus meta with the ability to shrink and enlarge objects, and he shrinks Cisco and Ralph while escaping. Harry's attempted cure backfires, and Caitlin determines that if they are not re-enlarged within a certain period of time, their bodies will explode. The team confronts Rundine at a warehouse, where Harry tricks him into re-enlarging Ralph and Cisco. Rundine is arrested, but refuses to confess to the earlier crime. Barry gathers that even if Ratchet went free, he would be as unhappy in the city as he is in prison; he wishes to live in a secluded Chinese village called Jiaju, but fears he will never get there. Barry then uses his speed to take Ratchet to Jiaju, where he can live out his dream. After discovering Barry is the Flash, the prison's warden, Gregory Wolfe, locks Barry in his private metahuman wing, intending to sell him to Amunet.

Wolfe plans to sell Barry and the imprisoned bus metas (Ramsey Deacon, Becky Sharpe, Mina Chaytan, and Sylbert Rundine) to Amunet, so they plan to escape. Cecile discovers Wolfe's plans after reading his mind. Ralph encounters a former colleague and his negative interaction with him prompts the discovery that he can shapeshift. His lack of mastery of the new ability prevents his attempt to foil Amunet's deal with Wolfe. Barry helps the metas escape the power dampeners, but they are cornered by Wolfe and Amunet. DeVoe arrives and again uses his chair to extract the metas' abilities, before transferring his mind into Sharpe's body. He then kills Wolfe as Marlize looks on in horror; Amunet flees. Ralph uses his shapeshifting ability to appear as the original DeVoe at Barry's appeal, claiming that he was unconscious at Barry's loft but not dead, which clears Barry's name. Team Flash realizes that DeVoe is only stealing powers from metahumans who were on the bus when the dark matter wave was unleashed, which means he will likely target Ralph as well. Back at the DeVoes' house, their marriage continues to deteriorate, and DeVoe drugs his wife with the Weeper's tears to maintain her devotion towards him.

Barry is put on indefinite leave at the CCPD due to his connection with the DeVoe case. The team encounter another bus metahuman named Izzy Bowin with sound wave abilities, amplified by her violin. She manages to use her abilities when DeVoe (inside Sharpe's body) comes to claim her. Barry and Ralph help to train Izzy to refine her abilities, which proves difficult when she gets hurt. Eventually DeVoe shows up once again, using Dominic's and Becky's abilities to make Barry experience a brain aneurysm, while using Rundine's abilities to incapacitate Ralph. DeVoe then once again uses the chair to transfer his mind into Izzy's body and escapes. Both Ralph and Barry comfort each other over their respective losses: Barry being let go from the police force and Ralph losing Izzy to DeVoe. These losses enforce both Barry's and Ralph's determination to bring DeVoe down and save the three remaining metas.

Jesse comes to Earth-1 to have a talk with her dad. Eco-terrorist Veronica Dale sets off a nuclear bomb, which Barry tries to stop, entering a form of superspeed known as Flashtime, where everything is frozen. However, the bomb has already detonated, and he and Jesse cannot stop it or save everyone with superspeed. Jay Garrick comes from Earth-3 to help, but they are still unable to stop it. Barry remains in Flashtime for hours, bringing each of his friends into it, in an attempt to find a solution; they discuss options such as freezing it or sending it to another Earth, but none of those solutions prove to be viable. Eventually, Iris gives him the idea to retrieve the Quark Sphere from the Speed Force to send a blast lightning through the bomb, enough to disable it. Barry does so, and throws the Sphere back into the Speed Force, saving Central City. Jay admits he is retiring and going to train a new "female" speedster. Jesse and Jay return to their Earths, and Caitlin and Wells go for a coffee, where they encounter the mysterious girl.

A metahuman with fire powers tries to rob Central City bank. Another bus meta named Matthew Kim touches the metahuman, which causes his powers to transfer to another individual. When Joe, Iris and Barry turn up to ask Kim a few questions, Barry and Iris come into contact with Kim, causing Barry to lose his speed and Iris to gain superspeed. Inspired by Thawne, Harry plans to build his own thinking cap to outwit DeVoe. With their roles reversed, Iris becomes Central City's hero speedster, while Barry must learn to act as team leader. The new metahuman demands money and terrorizes the city with his fire powers. Using Wells' thinking cap, the Team comes up with the idea for Iris to create a tidal wave, negating the flames and defeating the meta. Back at S.T.A.R. Labs, Kim touches Iris and Barry again, restoring the Flash's speed. At home, Iris admits that while she did enjoy having superspeed, Central City needs the light that Barry was, and she is happy being team leader. Wells uses his thinking cap once more, determining the final two bus metas are Janet Petty and Edwin Gauss.

Barry and Ralph train to defeat DeVoe, with Barry becoming annoyed at Ralph's apparent inability to be serious. The team manages to locate another bus meta, Janet Petty. When Barry and Ralph confront her, it is revealed that Petty can manipulate a person's gravitational pull, which she demonstrates on Barry. Fearing once again that Ralph is not taking things seriously, Barry refuses to work with him. Ralph reveals his comedic attitude is due to a difficult childhood where his father abandoned him, causing him to make jokes whenever he is scared or under pressure. Barry relents and they go to stop Janet at a gala event. Janet uses her powers on Barry, causing him to float into the atmosphere. Barry tells the team to trust Ralph to improvise. Ralph detains Janet, then becomes a giant airbag to allow Barry to land safely. DeVoe's wife discovers he has been drugging her, so she will continue to assist him. Breacher comes to Earth-1 to ask Cisco for help as some of his powers have failed. Harry takes the thinking cap to Thawne's time vault to recharge it and activates Gideon.

Team Flash track down the final bus meta Edwin Gauss, but are followed by the Samuroid, who injures Caitlin. The team rush back to Star Labs to regroup and heal. Caitlin reveals to Iris that Killer Frost is activated by her adrenal gland, and she is working on a way to separate them. Harry comes up with a tuning fork weapon that mimics Izzy's abilities in order to defeat DeVoe. Ralph reveals to Barry that he isn't afraid of losing his own life, but of Team Flash losing theirs, as he considers them family. Wells is shown to be addicted to the Thinking Cap, which Joe helps him deal with. Ralph takes the fork, with the intent to go with Edwin to kill DeVoe, which Barry argues against. Eventually, DeVoe manages to take over Edwin's mind, and as well takes the abilities of Janet Petty and Matthew Kim, before transferring his mind into Ralph's body. The team try to stop him, but DeVoe incapacitates them, and alters Caitlin's DNA, removing the dark matter and Killer Frost, before leaving. Back at his lair, DeVoe uses Ralph's morphing abilities to morph back into his original form, while he and Marlize plan their next move to destroy Team Flash.

With DeVoe moving forward with his plans, Team Flash decide to secure Neil Borman. Barry and Cisco travel to Earth-X to recruit Leo Snart as a backup, but are followed to Earth-1 by the Earth-X doppelganger of Laurel Lance. Team Flash plan to deliver Borman to a safe ARGUS facility, using a suit to contain the radiation, with Snart on hand, in case Borman goes nuclear. Snart agrees to help, but claims he can only stay for 24 hours, as he is due to get married to Ray Terrill. DeVoe attempts to intercept the transfer, but he and Team Flash are further ambushed by Earth-X Laurel, who kidnaps Caitlin, Borman and Joe, holding them at CCPD. Snart learns about Ralph, and convinces Barry to allow himself to grieve his fallen allies, which Barry eventually does, giving him strength to defeat Laurel. Lyla transfers Borman to another facility and Leo returns to Earth-X. Cisco and Wells come up with a plan to boost Wells' thinking cap. DeVoe goes more into his "god-complex"; stating that human emotion is a weakness, causing Marlize to doubt him.

DeVoe starts gathering the technology required to build the Enlightenment Machine, including murdering anyone who gets in his way. Barry, Cisco, Iris and Harry attempt to trigger Killer Frost's powers in Caitlin, but do not succeed. Harry reveals to the team that the amount of dark matter he used with the Thinking Cap caused brain damage. Cisco, Gypsy, Barry and Caitlin fight Marlize and DeVoe when they acquire the computers required to power the Enlightenment Machine. Flashbacks reveal partially why Marlize follows DeVoe: she was a humanitarian worker in Kenya who created a water purifier for a villager, but when warlords found out about it, they attacked and killed everyone. Marlize pleads with DeVoe when he begins choking Gypsy; she later decides to leave him, encasing his chair in a force-field so DeVoe cannot stop her from leaving the pocket dimension. The team realizes that DeVoe plans to use the Enlightenment Machine to launch dark matter towards Earth, reverting all of humanity into a simplified state, similar to what Harry is dealing with. The mysterious girl brings a gift to Cecile and Joe's baby shower and, after leaving quickly, runs away using speedster abilities.

After Harry is expelled from the Council of Wells due to his declining intelligence, Cisco assembles a Council of Harrisons to try and come up with a way of stopping Harry's intelligence loss. Team Flash reluctantly go to Amunet for help, encountering her successor Norvok in the process, though Barry insists Amunet must not kill. The team is eventually given a bomb made from Amunet's metal which will be capable of destroying one of DeVoe's satellites, and Harry manages to work out that DeVoe's plan might be changing because Marlize is no longer with him. Iris posts an article revealing DeVoe's plan and the residents of Central City begin reporting DeVoe sightings, which Iris believes will hamper his ability to remain undetected.

DeVoe infiltrates the A.R.G.U.S. facility holding Fallout by impersonating John Diggle and kills most of the security, except for a few hostages; overcharging and killing Fallout to be a nuclear battery for the satellites. Barry runs to Star City and brings back John to reveal the location of the facility. Caitlin and Cisco ask Barry to train them in Flashtime so that they can save the hostages and Barry can follow DeVoe through the breach before it closes. In the last stages of pregnancy, Cecile's telepathy causes her to take on the personality and thoughts of anyone nearby. Harry and Iris track Marlize to London, and use the last extrapolator to get there. Caitlin and Cisco are able to rescue the hostages. Searching her mind for Killer Frost, Catlin has Cisco vibe her into a repressed memory of a childhood accident; Killer Frost was already part of Caitlin decades before the particle accelerator had created any metas. Barry manages to follow DeVoe through the breach and destroys one of the satellites with Amunet's bomb. DeVoe takes control of S.T.A.R. Labs and uses its satellite to replace the one destroyed. He initiates the Enlightenment protocol in the time vault.

After the Enlightenment begins, Marlize joins Team Flash as Cecile goes into labor. Marlize uses Cecile's powers to send Barry into DeVoe's consciousness to find the good left in him. Barry finds Ralph alive in DeVoe's consciousness and together they find the "good" DeVoe dead. DeVoe attempts to keep them from reaching the nexus of his mind, as he follows Team Flash to a pocket dimension. In his consciousness, DeVoe multiplies himself to fight Barry and Ralph as he takes down Team Flash. Barry and Ralph make it to the nexus; Barry wakes up in the real world and Ralph reclaims his body just as DeVoe was going to kill Cecile. DeVoe reappears as a hologram through his chair until Marlize destroys it, killing him. Barry, Cisco and Ralph shield civilians from the falling satellites and the mysterious girl helps Barry destroy the last one. Harry's brain resets but is mostly restored by Marlize; he decides to return to Earth-2 to be with Jesse. Team Flash celebrates DeVoe's defeat with Wally (who returned from the Legends) and Cecile's newborn daughter Jenna. The mysterious girl arrives to reveal herself as Barry and Iris' daughter from the future, Nora; she claims to have made "a big, big mistake".

Team Flash meet Nora, Barry and Iris' daughter from the future. While Iris expresses excitement, Barry is concerned that she could alter the timeline based on his own mistakes with time travel. The Team encounters a new metahuman, Gridlock, who is able to harness kinetic energy, and Barry suits up in previous costumes since his last one was destroyed. When Barry tries to send Nora home, Wally reveals that Nora's blood is saturated with negative tachyons, which prevents her from using the Speed Force or the Legends' Waverider to time travel. Barry asks Nora what happens to him in the future, with Nora revealing that he never returns after disappearing in 2024 and that she traveled back in time to meet him. Gridlock causes a plane to fall, so Barry, Nora, Wally, and Cisco team up to stop it, with Nora providing Barry with a Flash ring suit. They phase the plane through solid structures before it lands safely in the river. While Gridlock is being transported to prison, the vehicle is attacked by a masked individual, who tells Gridlock that he plans to wipe out all metahumans before approaching him with a lightning-shaped dagger.

Barry struggles to train the overeager Nora, who gets herself hired as a CSI intern to spend more time with her father, much to Iris' discomfort. Caitlin and Ralph try to help Cisco in the aftermath of his breakup with Gypsy, with Cisco eventually accepting that Gypsy is not who he is meant to be with. Caitlin refuses to pursue the idea that her father might still be alive, despite Ralph's insistence. Cecile starts to lose her telepathy and struggles to connect with her child without being able to know her thoughts. Meanwhile, a new meta called Block, who can create blocks of dense air, steals weapons from her old gang, and while trying to stop her, the team has their first encounter with Cicada, the masked man who killed Gridlock. He stabs Block, but Nora manages to speed her away from the scene. Cicada then uses his dagger to neutralize the team's powers, beats them severely, and nearly kills Barry before Nora drives him off. Cisco vibes with Caitlin, learning that her mother is involved with her father's disappearance. Iris reveals that she has been investigating Cicada, and the team discovers that Nora already knows about him.

The team recruits Harrison Sherloque Wells to help them catch Cicada, who Nora reveals is unstoppable in the future. Caitlin and Ralph confront Caitlin's mother, who denies forging her husband's death certificate. They later break into her files and find a suicide note from Caitlin's father. Sherloque pinpoints Cicada as David Hersch, as he was previously correct 37 times. As a result of Nora's tampering with the timeline however, his identity on Earth-1 is different. Cicada attacks Joe to lure out Vibe and when Cisco arrives, Cicada stabs him and breaks his arm. Barry arrives, but is easily defeated. Nora enacts an explosion to drive Cicada off, which results in Cisco's apparent death. However, Cisco reappears, having used a breach machine to escape. With the public and Cicada believing that Vibe is dead, Sherloque agrees to help the team. Caitlin deciphers a hidden message from her father, Thomas, asking her to come find him. Cicada visits his comatose niece in the hospital. Nora agrees to stay with her parents, despite her seemingly strained relationship with Iris. Sherloque begins to suspect that Nora is not in 2018 for the reasons she gave.

The team discover articles about XS, written by one of Iris' former colleagues, Spencer Young, which are all published just before the events take place. Iris contacts Spencer, asking her to refrain from putting XS in her articles in order to protect Nora. Spencer is revealed to be in possession of a phone that allows her to control people's minds so she can create articles for her blog. Nora reveals she has a tense relationship with Iris because in the future, the latter implanted her with a meta dampening chip that limits her powers. Barry and Nora go to the stadium when a bomb threat is reported, where Spencer uses her tech to hypnotize XS into trying to kill the Flash. Iris eventually stops XS by shooting her with a tranquilizer dart, allowing Nora to regain her mind and Barry to arrest Spencer. The team discover that Spencer's phone and Cicada's dagger have meta abilities, created from DeVoe's satellite explosion, meaning meta-tech could be in the hands of anyone. It is later revealed that Cicada has super-strength.

Barry and Nora go to stop two criminals on motorcycles, with Iris getting frustrated when Nora cuts her coms. Nora reveals that in the future, Iris is always nagging her and never allows her to ask questions about her past. Nora goes to spend some time with Cecile, finding out more about Iris from her. Later, a new meta called Rag Doll attacks an architect downtown and destroys his office, though the Flash saves him. Iris and Barry try to investigate the new meta, but the latter gets captured by Rag Doll and held hostage on a rooftop with power dampening cuffs (though the villain's unaware of Barry's abilities). Ralph and Iris go to save Barry, with Iris jumping off the building herself to remove Barry's cuffs and allowing him to save them. Ralph swallows Rag Doll whole before becoming an airbag to land safely. Iris tells Nora nothing is off limits with her, and the two start to grow closer. Meanwhile, Cisco and Caitlin investigate her father and track him to a university office and a chem lab, but find nothing. Cisco successfully takes control of DeVoe's four satellites, which can be used to try and find both Caitlin's father's and Cicada's hideouts.

Barry, Cisco and Caitlin find her father, Thomas, in an arctic facility and bring him to S.T.A.R. Labs while the rest of Team Flash continue to investigate Cicada's identity. After his arm starts transforming into ice, Thomas reveals that in his attempt to cure his ALS, and to treat the ALS gene in Caitlin, the experiments resulted in them both developing ice powers, though his appears to be killing him, so Caitlin begins working on a cure to save him. Thomas claims he never manifested an alternate personality like Killer Frost, but Cisco is suspicious. He teleports back to Thomas' lab, where he discovers "Thomas" is actually an alternate personality wearing skin grafts to pose as him. Caitlin does not believe Cisco until she realizes the serum she created could kill her father's human side. Her father's alter ego "Icicle" emerges and attempts to kill Team Flash with absolute zero temperatures, but Caitlin proves to be immune. With the rest of the team incapacitated, Killer Frost returns and defeats Icicle. After the real Thomas briefly manifests, Icicle knocks Killer Frost back and escapes without the serum. Team Flash determines that Dominic Lanse / Brainstorm's powers caused Killer Frost's disappearance and they also learn the name of Cicada's niece, Grace.

Grace is in the hospital and Dr. Ambres impedes Barry to visit her. Barry and Nora must stop a freak lightning storm from hitting the city's power grid. Team Flash suspect Mark Mardon, though Nora and Barry encounter his estranged daughter instead, Joss Jackam/Weather Witch, wielding a weather control staff like her father. Barry and Nora bring Mardon to her in order to make her cease but to no avail. Instead, an angered Joss attacks an airport with a lightning tornado. Barry uses Mardon's wand to absorb Joss' lightning and subdue her. Team Flash finally discovers Cicada's identity: Orlin Dwyer. In flashbacks Orlin is shown adopting Grace after her mother's death in a metahuman attack and while bonding, debris from DeVoe's satellite puts Grace in a coma and impales Orlin with shrapnel that would later become his dagger. Blaming metahumans for what happened, Orlin vows to exterminate them all on Grace's behalf.

Barry and Nora time travel to gather items needed to stop Cicada; a highly magnetic alloy from Savitar's armor, Harry Wells' Speed Force transmitter, and dark matter. They first travel to Team Flash's final battle with Savitar. After a Time Wraith appears, Barry distracts it so Nora can retrieve a piece of the armor. They next travel to when Zoom stole Barry's speed for the transmitter, which Barry obtains from Harry. Zoom discovers Barry and Nora and gives chase before he is stopped by the Time Wraith; though this breaks the transmitter in the process. Even though he is reluctant, Nora convinces Barry to ask Eobard Thawne for help. Despite some initial difficulty, Barry convinces Eobard to fix the transmitter by claiming he will never get home if he does not. Finally, Barry and Nora travel to the night of the particle accelerator explosion. In the Time Vault, Gideon reroutes part of the dark matter through the shard and transmitter, and Barry reveals to Nora that Thawne killed his mother. Back in the present, Team Flash separates Cicada from his dagger temporarily before he escapes. Nora returns to 2049 to confront Eobard Thawne at Iron Heights.

This episode begins a crossover event that continues on Arrow season 7 episode 9, and concludes on Supergirl season 4 episode 9.