Barry discovers his powers and puts them to the test, only when he finds its no longer a test but the real thing when he encounters a certain someone.

Barry changes into the Flash when six gunmen storm a university event honoring a scientist, but his heroics don't match up to his expectations. Meanwhile, Iris becomes even more intrigued by the "red streak."

Barry is thrilled when Oliver, Felicity and Diggle come to Central City to investigate a case involving a deadly boomerang.

The crossover continues on Arrow S03E08 The Brave and the Bold.

Wells presents Barry with a life-changing choice. Dr. Martin Stein and Ronnie Raymond return to help the S.T.A.R. Labs team with this final fight.

Picking up months after the Singularity attacked Central City, Barry is still struggling to forgive himself for Eddie’s death. Concerned about putting his friends in danger, Barry has pushed everyone away and has chosen to protect the city on his own. When a meta-human named Atom Smasher attacks the city, Iris tells Barry that he needs to let his friends help him protect the citizens of Central City. Meanwhile, Cisco helps Joe with his Meta Task Force.

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.

The crossover continues on Arrow S04E08 Legends of Yesterday (II).

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).

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).