The alien Dominators land on Earth, and Barry realizes that he can't fight them alone. He summons Green Arrow and his teammates, and then the Legends, and then Supergirl from her Earth. However, the discovery of future-Barry's message forces Barry to reveal that he may have altered all of their lives when he changed the timeline, sowing the seeds of mistrust.

Barry finally tells Iris and the others--except Joe--what he saw in the future and together they set out to stop that future from coming to pass. Meanwhile, Caitlin invites Julian to join Team Flash, and H.R. prepares to open the museum.