John Thomas Stewart's great-great-grandfather brought back a cute eight-legged "hippo" Lummox from a space flight many years ago. The “hippopotamus” grew up and began to cause serious concern to the authorities. What do you want if swallowing a mastiff is like swallowing a fly for a frog? Lummox's life is under threat, but suddenly a spaceship comes after him, which can destroy the Earth in one gulp...