An evil shape-shifting cactus named Meglos hires some old, goofy space pirates to kidnap Arthur Dent from Earth. The evil cactus turns into an evil Arthur Dent and then into an evil Doctor! The cactus wants to take control of the Double-deckerhedron, a cheap prop of unimaginative power from a nearby planet that's inhabited by badly be-wigged aliens who built the artifact so long ago that some of them forgot and think it’s a god now. They argue about it a lot too.