The ultimate X-Men ensemble fights a war for the survival of the species across two time periods as they join forces with their younger selves in an epic battle that must change the past – to save our future.

When a cure is found to treat mutations, lines are drawn amongst the X-Men—led by Professor Charles Xavier—and the Brotherhood, a band of powerful mutants organised under Xavier's former ally, Magneto.

Cobb, a skilled thief who commits corporate espionage by infiltrating the subconscious of his targets is offered a chance to regain his old life as payment for a task considered to be impossible: "inception", the implantation of another person's idea into a target's subconscious.