Lem is just an average teenager working on getting the girl and furthering his career at the local planetarium - except that he's an alien. At least to U.S. astronaut Captain Charles T. Baker who lands on Lem's planet hoping for a quick flag plant and a hasty return to earth and his millions of screaming fans. But on this alien planet the media has tagged spacemen as brain-eating, zombie-creating monsters, causing Baker to run for his life and into Lem's house. Now it's up to the green native to get the clumsy astronaut back to his spaceship before military dictator General Grawl and mad scientist Professor Kipple manage to exterminate the Earthly visitor.

When Henry fails yet again to hand in his homework for the umpteenth time, he has no idea that this will set off a chain of events which will see him forming an unlikely alliance with Moody Margaret, the infuriating girl next door, and his irritating little brother Perfect Peter, outwitting corrupt School Inspectors and toppling an evil Headmaster, winning a talent contest and facing his ultimate nemesis with no way out - all because he is trying to save the very school which he has always professed to hate!