The Flash fights a villain from Earth-19 called Abra Kadabra, who offers to reveal Savitar’s identity in exchange for his release.

Barry and team are surprised when Mon-El and Hank Henshaw arrive on their Earth carrying a comatose Supergirl who was whammied by the Music Meister. Unable to wake her up, they turn to Team Flash to save her. However, the Music Meister surprises The Flash and puts him in a similar coma, one that Team Flash can’t cure. Kara and Barry wake up without their powers in an alternate reality where life is like a musical and the only way to escape is by following the script, complete with singing and dancing, to the end. This episode began in Supergirl S02E16.

Desperate to stop Savitar and save his friends, Barry turns to the Speed Force for answers. H.R. gives Jesse some advice.

While training with Barry, Wally starts to have visions of Savitar, which he hides from the team. A dangerous secret threatens Barry and Iris’ happiness.

When Grodd and his army of gorillas bring the battle to Earth-1, The Flash and team must find a way to stop them before they destroy Central City. Gypsy returns to join the fight. Meanwhile, Jesse Quick decides she wants to stay with Wally on Earth-1.

When Jesse Quick informs the team that her father has been abducted, Barry, Caitlin, Cisco and Julian voyage to Earth-2 on a rescue mission to save Harry from Gorilla City. As they trek through the forest, Barry and the team are immediately captured and brought to Grodd. Grodd tells them he needs their help to stop Solovar, the leader of Gorilla City, as Solovar wants to invade Earth-1. Meanwhile, back on Earth-1, Jesse and Kid Flash hit the streets to stop a metahuman that can control gravity, with H.R. and Joe guiding them from S.T.A.R. Labs.

Barry and the team at S.T.A.R. Labs work together to bring down Clive Yorkin, a criminal meta-human who is methodically killing people by causing them to decompose at an accelerated rate. Joe becomes his next target but it’s Iris who is caught in the crossfire. The Flash mentors Kid Flash and begins to elevate the newer speedster’s training to another level.

H.R.’s past catches up with him when a bounty hunter with vibe powers named Gypsy arrives in Central City to bring him back to Earth-19 to stand trial for his crime. It turns out inter-dimensional travel is illegal on their Earth. H.R. surrenders but when Barry and Cisco find out that H.R.’s only hope would be to challenge Gypsy to a fight to the death, they intercede and Cisco offers to fight Gypsy instead.

Barry is tormented by his vision of the future where Iris is murdered by Savitar. When a criminal named Plunder shows up in Central City, Barry recalls the villain’s presence in his vision of the future and fears that if he catches Plunder, it will cement Iris’ fate. Confused about Barry’s hesitation to stop Plunder, Wally decides to step in as Kid Flash. Caitlin offers Julian a job.

With Alchemy and Savitar still looming threats, Barry is unable to focus on the Christmas holiday, and especially his relationship with Iris. Determined to stop Savitar, Barry goes to Earth-3 to get advice from Jay Garrick. Wally wants to help Barry fight Savitar and reveals that he’s been training with H.R, which doesn’t go over well with Barry. As Cisco faces his first Christmas without his brother Dante, old wounds are reopened.

When aliens called the Dominators attack Central City, Barry speeds over to Star City to ask the Green Arrow for help in stopping them. Realizing the battle against the Dominators is bigger than they thought, they track down the Legends of Tomorrow, and Barry and Cisco create a breach to bring back a secret weapon – Supergirl. Once all of the super friends are assembled, they come up with a plan to attack but a shocking secret related to Flashpoint is revealed and suddenly no one is sure who they can trust. Meanwhile, Wally wants to join the battle against the aliens but Iris tells him he’s not ready.

The crossover starts on Supergirl S02E08 Medusa (I). It continues on Arrow S05E08 Invasion! (III) and DC’s Legends of Tomorrow S02E07 Invasion! (IV).

Caitlin uses her powers to save Barry but as her mother predicted, the effort unleashes her inner Killer Frost. Killer Frost goes on a rampage looking for Dr. Alchemy, kidnapping Julian and battling both The Flash and Vibe. Meanwhile, Joe and H.R. have a heart to heart talk.

When Wally starts having dreams about being Kid Flash, Barry realizes he has to tell Wally, Iris and Joe about what happened to Wally in Flashpoint in order to keep him safe.

Caitlin goes to her mother to help understand the meta-human powers growing inside her. Meanwhile Barry tries to convince Julian to allow him to help investigate a new human meta-attack on Central City.

Barry continues to train Jesse and when a new meta human, Mirror Master, appears on the scene he lets her tag along. Mirror Master has teamed up with his old partner, Top, and is looking for Snart to even a score. Jesse is quick to join the chase but defies one of Barry’s orders which results in disastrous consequences.

Barry and Team Flash are thrilled to reunite with Earth-2 Wells and Jesse. Wells confides to Barry and Caitlin that Jesse has all the powers of a speedster and has been saving people on his Earth. He is concerned about her safety and wants them to talk her out of using her powers. Meanwhile, Magenta, a new meta who can control metal, terrorizes the city.

Barry realizes the effects from Flashpoint are much greater than he thought. Meanwhile, Barry meets new co-worker Julian Albert and is surprised by Julian’s immediate disdain for him.

Barry is living his dream life – his parents are alive, he’s asked Iris West on a date and he can finally be a normal guy as Central City has another speedster, Kid Flash, running around saving the city. When Barry starts forgetting parts of his old life, the Reverse Flash taunts his nemesis and tells him that there will be serious repercussions for Barry and the ones he loves if he continues to live in this alternate universe. In addition to losing his memories, his powers will also start to fade. When disaster strikes, Barry must decide if he wants to continue to live in this world as Barry Allen or return to his universe as The Flash.

After Zoom reveals his true plan, Barry vows to do whatever it takes to stop him.

After Zoom unleashes an army of Earth-2 meta-humans on Central City, Barry is shaken when he sees their leader is the Black Canary’s Earth-2 doppelganger, the Black Siren. Meanwhile, Wally takes to the streets to help The Flash stop the meta-humans, which worries Joe. Iris and Henry are concerned about Barry taking on Zoom.

With Barry gone, the team must figure out a way to handle the return of an old enemy – Girder. Realizing Girder is retracing his steps from his last attack, Iris volunteers to act as bait to trap him in S.T.A.R. Labs. Meanwhile, Barry fights to return to his old life.

Zoom arrives back on Earth-1 intent on taking over Central City. Barry and Wells come up with a plan to stop Zoom once and for all but it’s extremely dangerous. Unsure if he should take the risk, Barry reaches out to both fathers for advice. Henry is adamantly opposed to Barry risking his life again but Joe thinks he can handle it which puts the two men at odds with each other. Meanwhile, Cisco is shocked when he vibes the Earth-2 villain Rupture, who happens to be his brother Dante’s doppelganger. Rupture came to this Earth seeking justice for Reverb’s death. Iris decides she’s finally ready to open up to Barry about her feelings for him.

A meta-human with super strength named Griffin Grey mistakes Harry for Earth-1 Harrison Wells and kidnaps him, demanding that Wells cure him from his current condition. Realizing another brilliant Wells could help track Griffin’s location, Barry asks Jesse to help. Meanwhile, Wally corners Joe about The Flash.

Equipped with the tachyon device, Barry believes he is fast enough to stop Zoom and wants to open the breaches to catch him. Harry strongly advises against that plan but after Barry convinces him, Harry reveals that Cisco has the power to re-open the breach. Meanwhile, Hunter Zoloman’s painful story on Earth-2 is revealed.

After the shocking revelation that Zoom is Jay Garrick, Barry is more determined than ever to get back to Earth-2 to stop Zoom forever. Desperate to find a way to increase his speed, Barry decides to travel back in time and masquerade as his earlier self in order to get his arch-nemesis, Dr. Harrison Wells/Eobard Thawne, to teach him how to run faster. However, things don’t go as planned and Barry is stunned to face familiar foe Hartley Rathaway, as well as old friend Eddie Thawne. Iris makes peace with her past in order to embrace her future.

Having arrived in town intent on creating maximum chaos, Trajectory’s antics are misinterpreted as having been perpetrated by the Flash himself. Barry thus must quickly! uncover the mystery of who is the girl under the mask — as well as what is driving her mad desire for speed and destruction

When King Shark escapes from an A.R.G.U.S.holding tank, Lyla and Diggle travel to Central City to warn The Flash. King Shark shows up at the West house and attacks Joe, Iris, Wally and Barry.

On Earth-2, the team races to find Zoom’s lair and asks for help from the most unexpected source. Meanwhile, back on Earth-1, Caitlin rushes to perfect Velocity-9 so that Jay can stop the Geomancer.

Barry, Wells and Cisco journey to Earth-2 to rescue Wells’ daughter, Jesse from Zoom. Barry is stunned when he runs into Earth-2 Iris and Joe, but nothing prepares him for meeting Killer Frost and Deathstorm. Meanwhile, back on Earth-1, Jay has to take over the Flash’s responsibilities when a meta-human nicknamed Geomancer attacks Central City.

Barry teams up with Wells to figure out a way to close the breaches, but they are distracted by a meta-human nicknamed Tar Pit who can transform into liquid asphalt. Iris is concerned for Wally’s safety after she finds out about his drag racing hobby. When he refuses to stop she makes a bold move that puts her in danger.

When Cisco gets a vibe of Eobard Thawne, Barry and the team don’t believe it. But, after an attack at Mercury Labs, Christina McGee confirms that the Reverse Flash is back. Meanwhile, Iris and Francine share a nice moment that brings Iris closer to her brother, Wally.

Now that they’ve grown closer, Barry considers telling Patty that he is The Flash. Meanwhile, Joe and Iris try to get to know Wally, and the team hunts down a meta-human who can slow time itself.

When Mark Mardon AKA The Weather Wizard returns to break Leonard Snart AKA Captain Cold and James Jesse AKA The Trickster out of Iron Heights, Barry must stop these rogues from taking over Central City during Christmas. Meanwhile, Joe and Iris meet Wally West.

Vandal Savage arrives in Central City and sets his sights on Kendra Saunders. After Vandal attacks Kendra and Cisco, they turn to Barry for help. Realizing how dangerous Vandal is, Barry takes Kendra to Star City and asks Oliver and team to hide her until he can figure out how to stop Vandal. However, things quickly go from bad to worse when a man with wings AKA Hawkman shows up and flies off with Kendra. Meanwhile, Harrison develops a serum to make Barry run faster and asks Jay to test it out.

Grodd returns to Central City and kidnaps Caitlin. Barry and team race to find her before it’s too late. Meanwhile, Cisco plans his first date with the new barista at Jitters, Kendra Saunders and Patty begins to suspect Barry is hiding something from her.

After recent events, Barry decides it’s time to confront Zoom and comes up with a dangerous plan. Caitlin sides with Jay and deems it too dangerous for Barry to engage with the speed demon. However, Iris shows her support and brings forth a surprising ally. We see what Earth-2 Harrison Wells’ life was like before coming through the breech.

Barry learns a new breacher, Dr. Light, has come through the portal and sets off to capture her. Jay tells Barry that Dr. Light was not a threat on Earth-2 and that Barry can reason with her. However, during a fight with The Flash, she blinds him and drops some shocking news about Zoom. Meanwhile, Barry and Patty go out on a date.

Barry and the team look for another Firestorm match for Dr. Stein. When the team meets Jefferson “Jax” Jackson, Caitlin has her reservations about whether Jax is the right match for Dr. Stein. Iris surprises Joe while Barry and Patty grow closer.

When Barry and the team find out Captain Cold has been kidnapped, they form an uneasy alliance with his sister, Lisa. However, Barry feels double-crossed when he finds out Snart is working with his father, Lewis Snart on a heist. Meanwhile, Joe is faced with a difficult decision.