Macabre aliens -- quite literally talking heads -- need a humanoid brain to replace a worn out computer in their spaceship. They capture Smith, but quickly realize that his brain is unsatisfactory. The aliens release Smith so that he can bring them somebody more suitable: "a small Robinson."

A small, crab-like robot heralds the arrival of a family of colonists from an alien race called the Taurons. John believes that they are peaceful settlers, but Smith insists that they are the vanguard of an invading army.