Challengers of the Unknown [Ace Morgan; Rocky Davis; Prof Haley; Red Ryan; Corinna Stark]; Machu; Major Cheever.
A space capsule plunks in the Atlantic, but the astronaut is strangled, killed in outer space! "Call the Challengers!" They've got their own problems. Red and Rocky fight over Corinna, and Prof feels useless recuperating from earlier wounds. At Cape Canaveral, they meet Major Cheever, a moon-walking astronaut. Corinna gets "weird vibes", wanders off, and gets locked in an airlock. Rocky breaks her free. Corinna holds a seance and summons a pink alien-ghost named Machu who lives on the moon! A live grenade interrupts. Who's sabotaging them? Ace, Corinna, Red, and Major Cheever make the next moon flight. (Rocky's too big for a spacesuit.) In space, Machu appears as Major Cheever pulls a gun! Cheever allied with Machu, who was left as a guardian to prevent men from venturing into space. But Machu thought all men evil, and now sees some are good. He forces Cheever to shoot himself, then dissipates. Ace pilots them home.