A space capsule plunks in the Atlantic, but the astronaut has been strangled. The Challengers are called to Cape Canaveral where they meet Major Cheever. Corinna gets weird vibes and so holds a seance which summons a being named Machu who lives on the moon. A live grenade interrupts. Ace, Corinna, Red, and Cheever make the next moon flight. In space, Machu appears as Major Cheever pulls a gun! Cheever had allied with Machu, who was preventing men from going into space. But now that Machu sees that some men are good, he forces Cheever to shoot himself, then dissipates. Ace pilots them home.