While the X-Men are at a summer camp, learning survival training, Mystique releases Cain Marko - the unstoppable Juggernaut - in hopes of getting his help in obtaining Xavier's mutant location system.

A news report from the Canadian mountains triggers something deep inside Wolverine, and he starts having berserk fits. To find out why, he takes the Blackbird to the site, not knowing that Kitty and Kurt are sitting in the back.