When Wally starts having dreams about being Kid Flash, Barry realizes he has to tell Wally, Iris and Joe about what happened to Wally in Flashpoint in order to keep him safe.

Caitlin uses her powers to save Barry but as her mother predicted, the effort unleashes her inner Killer Frost. Killer Frost goes on a rampage looking for Dr. Alchemy, kidnapping Julian and battling both The Flash and Vibe. Meanwhile, Joe and H.R. have a heart to heart talk.

With Alchemy and Savitar still looming threats, Barry is unable to focus on the Christmas holiday, and especially his relationship with Iris. Determined to stop Savitar, Barry goes to Earth-3 to get advice from Jay Garrick. Wally wants to help Barry fight Savitar and reveals that he’s been training with H.R, which doesn’t go over well with Barry. As Cisco faces his first Christmas without his brother Dante, old wounds are reopened.

Barry is tormented by his vision of the future where Iris is murdered by Savitar. When a criminal named Plunder shows up in Central City, Barry recalls the villain’s presence in his vision of the future and fears that if he catches Plunder, it will cement Iris’ fate. Confused about Barry’s hesitation to stop Plunder, Wally decides to step in as Kid Flash. Caitlin offers Julian a job.

While training with Barry, Wally starts to have visions of Savitar, which he hides from the team. A dangerous secret threatens Barry and Iris’ happiness.

Desperate to stop Savitar and save his friends, Barry turns to the Speed Force for answers. H.R. gives Jesse some advice.

Barry travels to the future to find out Savitar’s still unknown identity in the hopes of saving Iris. Upon his arrival in 2024, Barry encounters future versions of his Team Flash friends, who, following the death of Iris, have become very different people, profoundly impacted by their showdown with Savitar. It will be up to Barry to infuse a sense of hope back into the team, as he proves to be hero his future friends have been waiting for. Meanwhile, back in 2017, the hunt for Killer Frost continues.

Barry and the team meet Tracy Brand, a scientist, who may be the key to stopping Savitar. Unfortunately, Killer Frost is also after Tracy so Team Flash must battle their old friend, which proves to be particularly difficult for Cisco. Joe and Cecile’s relationship takes a big turn.

Barry takes drastic measures to stop Savitar. Meanwhile, H.R. continues to push Tracy Brand to design the trap for Savitar and Killer Frost returns with an interesting proposal.

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 nothing left to lose, Barry takes on Savitar.