When Cyclops and Nightcrawler save people from a car crash they question Xavier's desire to keep their identities a secret. Meanwhile, the Brotherhood terrorize people in a crowded stadium.

Avalanche wants to join the Institute, but has trouble being accepted by the others, especially after he's accused of taking joyrides on the X-vehicles at night.

The women form a team of crime fighters after Jean and Amara are teased for having weaker powers, and they call themselves the Bayville Sirens.

Mystique frees a mutant called the Scarlet Witch from an asylum, hoping she'll help the Brotherhood, but Mystique doesn't know the witch is seeking revenge on Quicksilver and Magneto.

At Xavier's urging, the Brotherhood and the X-Men unite to battle Magneto; and the Institute begins to self-destruct while students are trapped in the mansion.

A traitor in the battle threatens the efforts of the X-Men and the Brotherhood against Magneto, who has another secret weapon -- the Sentinel robot.

X-Men and the Brotherhood deal with the aftermath of the world finding out about mutants. The Institute is blown up, and Mystique posed as Prof. X to blow it up. Some of the X-Men and Brotherhood are captured, leaving the mutants that escaped to find them and the Professor.

Wanda receives a clue from one of Magneto's minions, Pyro, directing her to a ski resort. Meanwhile, Kurt is meeting Amanda's parents for the first time, and the Toad believes he can use Kurt's holo-inducer to disguise himself and win Wanda's love.

A mysterious female assassin terrorizes the X-Mansion, knocking out the X-Men one by one. Wolverine finds out that it is his clone, created by the Dr. Deborah Risman and raised without love by HYDRA, and she wants to kill him because she holds him responsible for her miserable life. Wolverine and X-23, as she is called, square off in a battle that Wolverine does not want to win.