When a powerful alien threat arrives on Earth under mysterious circumstances, Barry, Iris and the rest of Team Flash are pushed to their limits in a desperate battle to save the world. But with time running out and the fate of humanity at stake, Flash and his companions will also need to enlist the help of some old friends if the forces of good are to prevail.

Despero warns The Flash that great tragedies will befall the speedster and cause him to lose his mind. Once that happens, Armageddon will begin. Determined to prove Despero wrong, Barry doubles down on proving his innocence but a devastating revelation from Iris pushes him to the edge and sends him to seek counsel from Black Lightning.