ROBOT MONSTER

Ro-Man Extension XJ-2 (Barrows), referred to as just Ro-Man (a creature with an ape's body and what is often and erroneously described as a diving helmet for a head), has destroyed all human life on Earth with a Calcinator death ray, except for eight humans who remain alive. The survivors are a Professor (John Mylong), whose name is never mentioned; his wife (Selena Royle); their two daughters, Alice (Barrett) and Carla (Pamela Paulson); their young son, Johnny (Gregory Moffett); the Professor's assistant, Roy (Nader); and space pilots Jason and McCloud (neither of whom is seen or heard). Both pilots depart in a rocket ship for an orbiting space platform. All eight have developed an immunity to Ro-Man's death ray, having received an experimental antibiotic serum developed by the Professor.

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 destroys Jason and McCloud's spaceship, along with the space platform. He later strangles Carla, then tosses Roy over a cliff to his death.

Ro-Man's mission is waylaid, however, when he develops an illogical attraction to Alice and cannot bring himself to eliminate her. Great Guidance (referred to as "The Great One"), leader of the Ro-Man Empire, destroys both Johnny and Ro-Man with a Calcinator blast. The Great One continues the genocide with Cosmic June Rays, which cause prehistoric reptiles to appear (stock footage from the movie 1 Million Years B.C.); and psychotronic vibrations, which "smash the planet Earth out of the universe".

But Johnny is alive, having just awakened from a concussion-induced fever dream. Up to now, all that has happened has just been his nightmare. His sisters, their mother, and the two scientists, whom the family met while picnicking in Bronson Canyon, rejoice at finding him. Johnny and his family invite the scientists home for dinner; they accept.

Suddenly, the Great Guidance, his arms raised in a threatening manner, walks out of the cave directly toward the audience.

Ro-Man, an alien robot who greatly resembles a gorilla in a diving helmet, is sent to earth to destroy all human life. Ro-Man falls in love with one of the last six remaining humans, and struggles to understand how his programming can instruct him to kill her while his heart demands that he can't.