Ham III, the chimpanzee grandson of the first primate in space has spent his life clowning around as a circus performer. Having just discovered a mysterious new planet, The Space Agency recruits Ham as an astronaut, but more for publicity value than because he has 'the right stuff'. But when Ham and his fellow chimp astronauts arrive on planet Malgor, Ham finds the right stuff within himself as he rescues his new friends from the evil King Zartog.