The conclusion to Armageddon presents an opportunity for The Flash to end his lifelong battle with Reverse Flash, but the payoff could be too much for Barry and the team to handle; Mia Queen drops in from the future looking to save a lost loved one.

Barry is shocked when Eobard Thawne returns in the most unexpected way; Damien Darhk offers advice to Barry, but there is a catch; an epic battle begins with Reverse Flash pitted against The Flash, Team Flash, Batwoman, Sentinel and Ryan Choi.

Barry meets Black Lightning at the Hall of Justice after things take a dire turn with Despero; Iris suspects something is off with Despero's vision of the future so she seeks help from a powerful ally.

Despero warns The Flash that great tragedies will lead to Armageddon; Barry doubles down on proving his innocence, but a devastating revelation pushes him to seek counsel from Black Lightning.

When a powerful alien threat arrives on Earth under mysterious circumstances, Barry, Iris and the rest of the team are pushed to their limits in a desperate battle to save the world.