The X-Impulse. When Kitty Pryde discovers her mutant ability to phase through objects, she’s naturally frightened and confused. Life proves to be more difficult for Kitty when both Jean Grey and Lance Alvers, a.k.a. Avalanche, approach her. While Jean tries to recruit Kitty to Professor Xavier’s Institute, Alvers has plans of his own. Meanwhile, Sabretooth, Wolverine’s arch-nemesis, rolls into town and he’s looking for a fight!