Evil Moon robot Ro-Man Extension XJ-2 (Barrows), referred to as just Ro-Man, has seemingly destroyed all human life on Earth with a Calcinator death ray, except for eight humans that remain alive. The survivors are an older scientist (John Mylong), his wife (Selena Royle), his two daughters, his young son Johnny (Gregory Moffett), his assistant, and two space pilots that shortly take off in a spaceship for an orbiting space platform. All eight have now developed an immunity to Ro-Man's death ray, having received an experimental antibiotic serum developed by the scientist.