A mysterious new player enters the Marvel Universe...and the X-Men are square in the center of his crosshairs! What is the mission of Major X - and what does it have to do with the time-traveler known as Cable? It's a race against time to save mutantkind from certain devastation, but will Cable try to stop the deadly soldier and his far-reaching goals - or will he forge a tentative union with the mysterious military man? Writer/artist Rob Liefeld introduces a new wrinkle into the saga of Marvel's Mightiest Mutants! Join the X-Men as they ask the question that will soon be on everyone's lips: who is Major X?!