X-Men #5 picks up immediately from issue #4, with Professor Xavier shockingly de-powered in the X-Men's fight with Magneto. The Brotherhood has been driven off, and regrouped in an as-yet unnamed artificial asteroid. This marks the first visit of the X-Men to space - something that will become a mainstay of the series to the point that the recent Wolverine and the X-Men #6 has Wolverine run out of money and take his space plane to go and cheat at an intergalactic casino to raise funds for the school.
The main plot of this issue is driven by Magneto's wish to find out the X-Men's base of operations, something that ends up with Angel being kidnapped after an incident staged by Toad. The X-Men stow away on his ride back to space, and in the ensuing fight, the asteroid is destroyed. This provides a backdrop for some good action scenes and a nice character moment, with Wanda and Pietro refusing to acquiesce in killing the X-Men, but equally turning down their offer to join. In the end, the X-Men escape, apparently. Given that their escape craft is magnetically-powered and then immediately takes off again to pick up the Brotherhood from the soon-to-be-destroyed asteroid, I see a strong implication that Magneto himself saved the X-Men. Much later, we'll discover that Xavier and Magneto have history - history that perhaps explains why Mastermind and Toad are poking around Westchester in the first place. Is Magneto perhaps not being entirely straight with his subordinates?
And finally, we arrive at the last three panels, where we discover that Professor X was not really depowered at all. He was merely testing his students, who have now passed their final exam. Well, that was a bit quicker than I'd expected. I'll note that this "exam" involved Angel getting tortured.