The Dehyrates is a club of science fiction fans (also known as FENS) centered near the Bar-Z ranch owned by Spurs Jackson. While Spurs and Strong Bow are away investigating a situation on the moon, Hank Roper is instructed to meet the Dehyrates, who are to arrive in a plane mocked-up like a spaceship. When Neptunian Artopods show up in their spacecraft, Hank initially mistakes the Artopods for costumed Dehyrates. Soon it becomes clear the Artopods are a scouting party for an alien invasion of Earth.