Koomasta herännyt Barry alkaa taistella uuden yli-inhimillisen nopeutensa avulla toista metaihmistä vastaan, joka käyttää säävoimiaan pankkien ryöstelyyn.

Barry osallistuu Iriksen kanssa palkintoseremoniaan, jonne hyökkää aseistautuneita miehiä. Taistelussa hänen uuden supervoimansa sivuvaikutukset alkavat näkyä.

Nuoli ryhtyy auttamaan Salamaa tappavan bumerangin tapauksen selvittämisessä, mutta tunteita hallitseva metaihminen kääntää Salaman entistä ystäväänsä vastaan.

Tohtori Wells tarjoaa Barrylle houkuttelevan tilaisuuden palata ajassa taaksepäin pelastamaan äitinsä. Teolla voi kuitenkin olla katastrofaaliset seuraukset.

Singulariteetista on nyt kuusi kuukautta, Salaman tiimi on hajonnut ja jättänyt Barryn S.T.A.R. Labsiin yksin taistelemaan metaihmisiä vastaan.

Vandal Savage on uusi uhka Central Citylle – hän on vaarallinen ja voimakas, muttei kuitenkaan metaihminen. Barry pyytää Nuolta apuun.

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.

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.

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).

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 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.

The crossover starts on Supergirl S02E16 Star-Crossed (I).

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

With only 24 hours left until Savitar murders Iris, Barry struggles to save the woman he loves and makes the choice to use any means necessary to do so. Realizing he has one option left to save her, The Flash turns to Captain Cold for help.

With Barry in the speed force, Iris, Kid Flash, Joe and Vibe have taken over protecting Central City. However, when a powerful armored villain threatens to level the city if The Flash doesn't appear, Cisco makes a risky decision to break Barry out of the speed force. However, the Barry that comes out isn't the same Barry that went in.

Barry and Iris's wedding brings the gang together, but things go awry when villains from Earth-X attack the ceremony. All of the superheroes band together with help from their super friends like Citizen Cold, The Ray, Felicity Smoak, Iris West and Alex Danvers to take on their most formidable villains yet. Earth's mightiest heroes - Green Arrow, Supergirl, The Flash and White Canary - lead their teams into battle to save the world.

The crossover starts on Supergirl S03E08 Crisis on Earth X (I) and Arrow S06E08 Crisis on Earth X (II). It continues on DC's Legends of Tomorrow S03E08 Crisis on Earth X (IV).