or, a great deal of incest
The evil alien “Ro-Man” has destroyed all but eight humans on Earth with his death ray, the “Calcinator”. Survivors include a family of five, a scientist, and two unseen assistants to the scientist in a spacecraft bound for an orbiting space platform carrying a garrison of human soldiers. All eight have developed an immunity to the death ray as a side effect of an antibiotic serum developed by the scientist. Ro-Man must destroy these survivors before his invasion of earth is complete. He is waylaid in his mission after developing an attraction towards Alice (earth babe), the eldest daughter of the family. He refuses to eliminate her, forcing “The Great Guidance”, leader of the aliens, to personally finish the unsavory task.