Season synopsis
Contains spoilers for this season and earlier seasons.
The season opens with Ronnie Raymond and Martin Stein combining as Firestorm to destroy the singularity over Central City; Ronnie is lost in the effort. Six months later, Barry has withdrawn from his friends and works alone until a speedster from another Earth arrives. Jay Garrick says he is the Flash of Earth-2 and warns that Zoom is sending metahumans through breaches to kill Barry. The team reunites around the threat, while Harrison Wells of Earth-2 joins them to rescue his daughter Jesse, whom Zoom holds captive.
Barry and his allies travel to Earth-2, where Zoom's attacks expose the multiverse's dangers. They eventually learn that the Jay who has been working beside them is really Hunter Zolomon, an Earth-2 serial killer posing as that world’s Flash under the stolen name Jay Garrick. Hunter has used the speed drug Velocity-9 and a time remnant to stage his supposed death, then returns to Earth-1 with Caitlin and plans to conquer the other worlds. Barry loses and regains his speed through the Speed Force, while Wally West learns Barry’s identity and becomes more involved with the team.
Zoom assembles an Earth-2 army and kills Barry's father, Henry, in front of him. Barry nearly gives in to revenge, but his friends stop him from racing Hunter in anger. Zoom abducts Joe and threatens to destroy the other Earths with a magnetar powered by both speedsters. Barry creates a time remnant that frees Joe and sacrifices itself to disable the device; the original Barry defeats Zoom, who is taken by Time Wraiths. The captive in Zoom's iron mask is the real Jay Garrick, Henry's Earth-3 counterpart. Grieving, Barry travels to the night his mother died and saves her, setting up the Flashpoint timeline that opens season 3.