Evil Moon robot Ro-Man Extension XJ-2 (George Barrows), referred to as just Ro-Man, has seemingly destroyed all human life on Earth with a Calcinator death ray, all except for eight humans that remain alive. The survivors are an older scientist (John Mylong), his wife, 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.
Ro-Man must complete the destruction of all humans, even if it means his physically killing them one-by-one, before his mission to subjugate the Earth is complete. After fruitless negotiations, Ro-Man, with a laser in hand, destroys the spaceship headed for the orbiting platform, killing the two pilots aboard. He later strangles the youngest daughter, Carla (Pamela Paulson), and tosses the assistant scientist, Roy (George Nader), to his death over a cliff.
Ro-Man's mission is waylaid, though, when he develops an illogical attraction to Alice (Claudia Barrett), the scientist's eldest daughter. He refuses to eliminate her, forcing the alien leader, The Great Guidance, to teleport to Earth after first killing the disobedient Ro-Man. The Great Guidance then attempts to finish the genocide by releasing prehistoric dinosaurs and a massive earthquake on the remaining survivors.
But Johnny is alive, having just awoken from a concussion-induced fever dream. Up to now, all that has happened has just been his nightmare. His parents, who had been looking for him, rejoice and take him home.
Suddenly, Ro-Man, his arms raised in a threatening manner, rushes out of a cave.[Note 1]
How does the Great Guidance attempt to finish the genocide by releasing prehistoric dinosaurs and what else?
massive earthquake