The movie kicks off with a shocking cosmic event as multiple Earths across the Multiverse face imminent annihilation. This catastrophe is orchestrated by an enigmatic and powerful entity known as the Anti-Monitor, who seeks to absorb all realities into his own dark dimension. The Superheroes of Earth-1, led by Superman, Batman, and Wonder Woman, are quickly mobilized. Meanwhile, The Flash (Barry Allen) discovers that his abilities to traverse between dimensions make him pivotal in the coming crisis. As reality begins to crumble, desperate calls go out to heroes from alternate dimensions, rallying them to unite against this overwhelming threat.

Various legendary superheroes, including Green Lantern, Aquaman, and Martian Manhunter, combine forces with their counterparts from Earth-2 and other parallel universes. Complex interdimensional alliances form, and tensions arise as different heroes grapple with trust issues and divergent strategies for tackling the Anti-Monitor's onslaught. Amid the chaos, secrets are unveiled, relationships tested, and sacrifices become inevitable. The atmosphere is already strained when a crucial piece of intelligence reveals a flicker of hope—but only if these heroes can navigate their differences and come together before reality itself is obliterated. The clock ticks down as they brace for an all-out battle that will determine the fate of countless worlds.