The story is set in a futuristic 1973. A rescue mission arrives on Mars to retrieve (Marshall Thompson), the lone survivor of the first manned mission.

Played by Ray "Crash" Corrigan in a rubber suit, the creature is portrayed as a "vampire" that sucks its victims dry of blood and glandular fluids to survive in the arid Martian environment.

Carruthers is suspected of murdering his crew to survive, though he insists a Martian monster was responsible.