Professor Xavier, the mentor of the X-Men is forced to confront his past sins when his own son explodes into a destructive force, and Jean Grey turns to the dark side, forcing the team to strike down one of their own in order to save themselves and the world. The death of one of their own leaves the remaining X-Men struggling to deal with the loss. And even before a moment of silence can pass, the mysterious Mr. Sinister arrives, intent on giving the X-Men a lot more to mourn.
