Mutilation murders occur with increasing savagery in a city. The nature of these murders - vital organs ripped from the victim's bodies - leads the C.I.A., headed by Holman (Wendell Corey) to the conclusion that the former chief of the Astro Space Laboratory, Dr. DeMarco (John Carradine) has succeeded in creating an Astro-Man, a zombie with a defective brain! DeMarco, missing since his dismissal from the Space Center, has secreted himself in an old mansion on the outskirts of the city, there he continues his experiments on human bodies with the aid of a deformed assistant. Foreign agents from hostile governments are also trying to locate DeMarco to force him to put his knowledge in their hands. The exotic and voluptuous Satana working with two vicious killers reduce the competition by torture and threat, brutally massacring some of Holman's men. The subsequent mutilation of a beautiful technician at the Space Lab, leads Holman to set a trap for the zombie, by planting another girl as bait. The suspense tightens when the zombie attacks the girl after Holman's men are gone. After a desperate fight the zombie is tracked down, back to DeMarco's mansion. Meanwhile the spies are embroiled in ever deepening intrigue, but manage to find DeMarco's lab with a frequency rectifier. An explosive finale is inevitable. Holman's men surround the mansion, trapping Satana inside with DeMarco and the zombies. A bloody gun battle follows, with the zombies butchering indiscriminately. DeMarco is shot down by Satana but not before he throws the master switch that deactivates the zombies forever, burying his secret under a mass of electronic rubble.