WATCH X- MEN 3 TRAILER

It begins with a scene from 20 years ago where Charles Xaiver and Magneto (who were friends at that time) go to see Jean Grey. They talk to her and Charles asks her whether she will control her powers, or if her powers will control her. Magneto, however, seems fascinated with her power.

A pharmaceutical company called Worthington Labs announces that it has developed an inoculation to suppress the X-gene that gives mutants their powers and makes them different from humans, offering the "cure" to any mutant who wants it. While some mutants are interested in the "cure", including the X-Men's Rogue, many others are horrified by the announcement. In response to the news, the X-Men's adversary Magneto raises an army, warning his followers that the "cure" will be forcefully used to exterminate the mutant race.

Cyclops, still depressed about the loss of Jean Grey, returns to Alkali Lake, where Jean sacrificed herself to save the X-Men. Jean appears to Cyclops, and as the two kiss, Jean changes and appears to kill Cyclops. Sensing trouble, Professor Charles Xavier sends Wolverine and Storm to investigate. When they arrive, the two X-Men encounter telekinetically floating rocks, Cyclops' glasses, and an unconscious Jean.

Xavier explains that when Jean sacrificed herself, she unleashed the powerful alternate personality she calls "Phoenix". Wolverine is disgusted to learn that Xavier has kept Jean in check telepathically, but when Jean awakens, he realizes she is not the Jean Grey he knew. Jean pleads with Wolverine to kill her, but when he refuses, the Phoenix surfaces and telekinetically slams Wolverine into a wall. She then escapes to her childhood home.

Magneto, also aware that Jean is now a powerful mutant, meets Xavier at Jean's house. The two men vie for Jean's loyalty until the Phoenix resurfaces, unleashing her devastating power. She destroys her family's house, disintegrates Xavier, and leaves with an uneasy Magneto.

After the professor's demise, the X-Men regroup and confront Magneto's army, which is attacking the pharmaceutical company's laboratory on Alcatraz Island. During the fight, Beast injects Magneto with the "cure", nullifying his mutant powers. After the battle, the Phoenix emerges and begins to destroy everything and everyone around her. Momentarily gaining control, Jean begs Wolverine to help her. Telling Jean he loves her, Wolverine kills her with his claws.
Phoenix unleashes her power.Despite the X-Men's losses, life goes on. Magneto, now an ordinary man, sits at a chessboard in a park and reaches out toward a metal chess piece. The piece trembles slightly. Following the end credits, Dr. Moira MacTaggert checks on a comatose patient who greets her with Xavier's voice. Startled, she replies, "Charles?"