The X-Men return from Genosha, finding the home destroyed, and Professor Xavier missing. They suspect a super-strong Russian mutant named Colossus, but the real culprit turns out to be someone more human, far tougher, and with deeper ties to the Professor.

An ancient and immensely powerful mutant, known as Apocalypse, creates four Horsemen to help usher in a new world where survival of the fittest reigns.