Xavier leaves Earth with the mutant Skrulls to become their teacher. The High Evolutionary decides that the best way to solve the mutant problem is to eliminate the mutant gene and turn them all into normal humans. And he does so.
The X-Men cope with the loss of their powers and get on with life. Mr. Sinister betrays the High Evolutionary and prepares to accelerate mutations in every human on Earth.
The powerless X-Men launch an assault against the High Evolutionary's satellite to keep Sinister from driving mutations on Earth wild. The day is saved and powers return.