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 enjoys the annual tradition of tree trimming and gift exchange with Joe and Iris. He gives Iris a touching gift, but the moment is interrupted by Eddie’s arrival.

While Barry, Harrison, and Caitlin hunt down Ronnie, who has attacked a man, Joe recruits Cisco to help him learn the truth about who murdered Nora Allen.

When a villain calling himself the Trickster runs rampant in Central City, Joe and Barry go to Iron Heights to talk with the original Trickster.

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.

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.

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

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).

With nothing left to lose, Barry takes on Savitar.

Barry and Team Flash come up with a plan to stop Cicada. However, the plan calls for Barry and Nora to travel back in time to gather some key necessities. However, Barry hesitates, concerned about his daughter seeing certain parts of his life. Meanwhile, Sherloque takes his concerns about Nora to Iris, and Caitlin turns up a key asset in the fight against Cicada.

Team Flash is under attack, and each must fight to save not only themselves but each other.

As Iris receives word of a career milestone, Barry is suddenly nowhere to be found. In trying to get back home, Barry runs across many familiar faces. Khione continues to figure out her powers, and Chester works on a suit for Allegra.