In a world where mutants with extraordinary abilities are ostracized by society, a pharmaceutical company announces that it has developed a "cure" for the mutant gene, capable of stripping mutants of their powers and rendering them "normal." The controversial cure quickly divides the mutant community. While some see it as an opportunity to assimilate into society, others perceive it as an eradication of their identity and a tool for mandatory conformity. The mutant community's conflicting views on the cure lead to tension and mistrust, as the possibility of choosing between their powers and societal acceptance looms.

Magneto, the powerful mutant with control over metal, sees the cure as a threat to the survival of mutantkind and mobilizes his Brotherhood of Mutants to oppose it by any means necessary. Meanwhile, the X-Men, led by Professor Charles Xavier, face their own internal struggles as they contend with the implications of the cure on their lives and their mission for peaceful coexistence. The emergence of Jean Grey, one of the original team members who has returned with vastly amplified, but extremely unstable powers, further complicates the situation. As lines are drawn and sides are chosen, a full-fledged battle looms on the horizon, with the potential to decide the future of humans and mutants alike.