UltraMax is the new orbiting prison for ultraviolent offenders. When the X-Men learn that their former teammate Longshot is among the prisoners, Rogue goes undercover to try to liberate him. Soon, the X-Men discover UltraMax's deadly secret--its mastermind is Mojo, the insane other-dimensional villain whose idea of entertainment is both visionary and deadly. Trapped behind prison walls with no escape, the X-Men face their most terrifying threat ever.