In the future, Earth is a polluted wasteland. People have resorted to drugs and promiscuity while relying on off-world food production systems for salvation. Research chemists Major Adam (Kirk Douglas), his young assistant/lover Alex (Farrah Fawcett), and their dog Sally are the sole residents of the subterranean Experimental Food Research Station on Saturn's third moon, Titan. Unable to maintain quota for the last three years, Earth decides to dispatch another scientist to help them meet Earth's food needs.

That scientist is a mentally unstable opportunist, Captain Benson (Harvey Keitel), a flunky from astronaut school who usurped the pilot position after killing the intended dispatch, Captain James. While Saturn 3 goes into a 22-day blackout period in the eclipse, Capt. Benson's puts together the first of a new line of "demigod series" helper robots, Hector.  Hector's memory utilizes unprogrammed human brain tissue and receives its programming via a connection to an electric probe in Benson's head. Unfortunately, Hector also assumes the same traits of Benson, a flawed, murderous, lustful individual who secretly desires to take over the lab and use Alex for his pleasure. Hector has no such secret, proceeding to terrorize all three of the humans in his quest for dominance.

Stanley Donen directs from a Martin Amis script, based on a story by John Barry.