The world is under attack by an alien armada led by the powerful Apokoliptian, Darkseid. A group of superheroes consisting of Superman, Batman, Wonder Woman, The Flash, Green Lantern, Cyborg, and Shazam must set aside their differences and gather together to defend Earth.

The Flash finds himself in a war-torn alternate timeline and teams up with alternate versions of his fellow heroes to restore the timeline.

After the events of Justice League: War, Ocean Master and Black Manta have declared a war against the surface in retaliation of the aftermath of Apokoliptian-tyrant Darkseid's planetary invasion. Queen Atlanna seeks out her other son, Ocean Master’s half-brother Arthur Curry, a half-human with aquatic powers with no knowledge of his Atlantean heritage, to restore balance. Living with powers he doesn’t understand and seeing the danger around him, Curry takes steps to embrace his destiny, joining the Justice League, and with his new teammates he battles to save Earth from total destruction.