Full story
In ancient Egypt, the mutant En Sabah Nur rules like a god. During a ritual to move his mind into a new body with a healing factor, a group of rebels brings the pyramid down. His four followers, the Horsemen, die, and he is buried and dormant for thousands of years.
In 1983, CIA agent Moira MacTaggert investigates a cult in Cairo and accidentally wakes En Sabah Nur, now called Apocalypse. He is appalled by the modern world and decides to wipe it out and start over. He recruits new Horsemen and amps up their powers: young thief Ororo Munroe, fighter Psylocke and Angel, who gets metal wings. Meanwhile, Scott Summers, Alex's brother, arrives at Xavier's school after his eye beams kick in. He meets Jean Grey, who has nightmares about a destructive power inside her. Mystique, now a hero to many young mutants, rescues Kurt Wagner from an underground fight ring in Berlin.
In Poland, Erik is living under the radar with his wife and daughter. He uses his powers to save a coworker at a factory and is exposed. The police accidentally kill his family, and Erik kills the officers. Apocalypse finds him at rock bottom, takes him to Auschwitz and shows him how strong he really is. Erik becomes the fourth Horseman.
When Xavier uses Cerebro to find Erik, Apocalypse hijacks his mind and makes every nation fire its nuclear missiles into space. The Horsemen kidnap Xavier. Alex tries to fight back and the mansion explodes. Peter Maximoff arrives just in time to save everyone with his speed, except Alex. Colonel William Stryker hauls Mystique, Hank, Moira and Peter off to Alkali Lake. Scott, Jean and Kurt follow, and there Jean frees Weapon X, a Logan with no memory, who tears through the base before running into the woods.
Erik shifts Earth's magnetic field and starts tearing cities apart. In Cairo, Apocalypse begins the body transfer with Xavier, who loses his hair in the process. The X-Men arrive and fight. Angel dies in a plane crash. Mystique convinces Erik to switch sides, and Ororo turns on her master too. Xavier battles Apocalypse inside his mind and tells Jean to let it all out. Jean unleashes the fiery power she had been holding back and turns Apocalypse to dust. Erik and Jean rebuild the mansion, and Xavier gives Moira her memories back. Erik leaves. Mystique and Hank start training a new team. After the credits, men put Weapon X's blood in an Essex Corp briefcase. That thread is left open.