| Director | Edward L. Cahn |
|---|---|
| Genre | horror film, monster film, science fiction film |
| Runtime | 68 min |
| Country | United States |
In 1973, a nuclear-powered spaceship blasts off from Mars for Earth, bringing with it the sole survivor of the first mission, Col. Edward Carruthers. He is suspected of having murdered the other nine members of his crew for their food and water rations, on the premise that he had no way of knowing if or when an Earth rescue mission would arrive. Carruthers denies this, attributing his crew's deaths to a hostile humanoid life form.
Commander Col. Van Heusen is unconvinced and ensures that Carruthers is constantly accompanied. While the ship was on the Martian surface, a hatch had been left open, allowing the creature access. The crew is skeptical that something crawled aboard. When Kienholz investigates sounds from a lower level, he is killed and his body hidden in an air duct. Next, Gino Finelli is found barely alive, and the creature attacks his would-be rescuer. Bullets have no effect, forcing the crewman to leave Gino. An autopsy reveals Kienholz's body has been sucked dry of all fluids.
The creature proves to be immune to hand grenades and gas grenades. Electrocution also has no effect. The crew lure "It" into the atomic reactor room and expose the creature directly to the nuclear pile. It easily crashes through the heavily shielded door and escapes. The survivors retreat to the control room. Carruthers notices the ship's higher-than-normal oxygen consumption rate and surmises that the creature has larger lung capacity, needed for the thin Martian atmosphere. The crew don their spacesuits, and Carruthers opens the airlock directly to the vacuum of space. In a violent decompression "It" suffocates, stuck part way through the final hatch.
A press conference on Earth reveals what happened aboard the rescue ship. The project director emphasizes that Earth may be forced to bypass the Red Planet, "because another word for Mars is Death".