Full story
In 1944, at a concentration camp in Poland, young Erik Lehnsherr bends a metal gate as he's torn from his mother. Nazi scientist Klaus Schmidt sees it and wants the boy's power. To force it out, he kills Erik's mother in front of him. Erik erupts in rage and wrecks the room. Around the same time, in the United States, young telepath Charles Xavier meets Raven, a blue shapeshifting girl, and takes her in as a sister.
In 1962, Charles is finishing his doctorate at Oxford while Erik hunts escaped Nazis to get to Schmidt. The villain now goes by Sebastian Shaw, absorbs energy and runs the Hellfire Club with Emma Frost, Azazel and Riptide. CIA agent Moira MacTaggert finds out Shaw is manipulating American and Soviet officers and goes to Charles. During an operation at sea, Charles saves Erik from drowning as he tries to drag Shaw's yacht down. That's where the friendship starts.
With Cerebro, built by young scientist Hank McCoy, they recruit other mutants: Banshee, Havok, Darwin and Angel. Shaw raids the CIA base, kills Darwin and takes Angel. Charles and Erik set up training at the Xavier family mansion. Erik learns to control his power in the space between rage and calm, and Raven struggles with how people see her. Hank tries a serum to hide his looks but turns into Beast, blue and furry.
Shaw's plan is the Cuban Missile Crisis: a nuclear war that would wipe out humans and leave mutants on top. The X-Men head to the naval blockade, Erik pulls Shaw's submarine out of the sea and the two groups fight. Erik puts on Shaw's telepathy-blocking helmet and kills him with the same coin from the day he lost his mother, driving it through Shaw's forehead.
Ships on both sides open fire on the mutants. Erik turns the missiles around in midair and Moira shoots at him. Erik deflects the bullets, and one hits Charles in the spine. He will never walk again. The friends split: Raven chooses Erik and takes the name Mystique. Charles opens the school at the mansion and wipes Moira's memory. Erik breaks Emma Frost out of prison, takes the name Magneto and forms his brotherhood. The rivalry is left hanging and comes back later.