The X-Men found themselves in a power vacuum with Cyclops missing and presumed dead, and Charles Xavier leaving the team to transport marooned young Super Skrulls to a new home in space.
At the team's weakest moment, the High Evolutionary struck (guided by Mr. Sinister, in disguise as his university mentor). The villains released a wave of energy that depowered mutants across the globe!
Not only did mutants lose their powers, but they lost any physical benefit of their mutation - wings, tails, and even enhanced muscles rapidly faded away. Cable's body was ravaged by his techno-organic virus, Cannonball plummeted from the sky in San Francisco, and an Adamantium-poisoned Wolverine needed the New Warriors help in polishing off a B-list villain.
The X-Men scattered to the winds to enjoy time off from their powers, but they were brought back together by Beast. Beast had been on the ground with Iceman in Genosha with Magneto and Polaris, trying to defeat Magistrates intent on exterminating their suddenly depowered prey. While there, Hank observed a new wave of rapid, destructive mutation in the Genoshan mutates that he feared would quickly emerge in the human populace around the globe
Convinced the new wave of mutation would cripple humans around the world, the de-powered X-Men staged an assault on the High Evolutionary's satellite base. Once on board they were beset by rapidly grown New Men, but Wolverine, Kitty, and Storm slip away from the battle when Wolverine catches Mr. Sinister's scent. (Kitty wonders, "Scent?" - as Wolverine's enhanced senses were part of his mutant power.)
The trio engaged Sinister, who wrestled control of the station from his former student to launch the crippling wave of rapid mutation. In the midst of their struggle with Sinister, Kitty noticed Wolverine was resisting extreme heavy damage and realized they were now out of reach of the depowering energy wave.
With Kitty's advice that their powers returning, Storm and Wolverine made quick work of Sinister, who promptly fled the scene in the X-Men's ship. High Evolutionary admitted both his defeat and his wrong-doing, and disengaged both energy waves. He offered the X-Men a shuttle back to Earth.
Back on Earth, a repowered Polaris masqueraded as Magneto in Genosha, thanks to an image inducer and a mysterious transfusion of power between her and the master of magnetism!