Dr. Cal Meacham receives a mysterious book with metallic pages that instructs him on how to build a device called an "interociter". Once completed, the device allows him to communicate with an alien named Exeter, who is distinguished by his large forehead, indicating a large brain. Meacham is transported to a hidden research facility by an unmanned plane, where he reunites with his old flame Dr. Ruth Adams. Together with other geniuses, they have been gathered to assist Exeter in his experiments. Upon realizing that Exeter and his assistant Brack are aliens, Meacham and Adams attempt to escape in a car, but instead they are beamed into a flying saucer and taken to the planet Metaluna. There they learn from the leader "The Monitor" that the planet is under attack by the evil Zagons and that Metalunans are trying to relocate to Earth. They are held captive by mutant insect-like humanoids in a vast underground city and unable to escape.