Astronauts Glenn and Fuji investigate Planet X and encounter mysterious aliens known as the Xiliens, who ask Earth's people to help save their world from "Monster Zero". In exchange for borrowing Godzilla and Rodan, the Xiliens offer a cure for cancer. As Glenn investigates, he develops a romance with Miss Namikawa and uncovers the Xilien's true intentions.

Cast: Akira Takarada, Nick Adams, Kumi Mizuno, Keiko Sawai, Jun Tazaki, Yoshio Tsuchiya