In 1973, a nuclear-powered spaceship blasts off from Mars for Earth, carrying with it the sole survivor of the first mission, Col. Edward Carruthers. He is suspected of having murdered the other nine crew members to hoard their food and water rations, a theory born from the grim uncertainty of whether any Earth rescue would ever arrive. Carruthers denies the accusation, insisting that a hostile humanoid life form on the Red Planet is to blame for the crew’s deaths.
Commander Col. Van Heusen remains unconvinced and orders that Carruthers be constantly accompanied by another crew member, turning suspicion into constant vigilance. On Mars, an emergency hatch had been left open during the surface mission, granting the intruder easy access to the ship. At first, the crew is skeptical that anything could have crawled aboard, but fear grows as odd noises from a lower level are investigated.
Kienholz is the first to fall when the creature stalks him, killing him and stashing his body in an air duct. Next, Gino Finelli is found alive only in a precarious state; the creature strikes at his would-be rescuer, and bullets prove useless, forcing the crewman to leave Gino behind, much to the distress of his brother Bob Finelli. An autopsy on Kienholz’s remains reveals a chilling sight: the body has been drained of all fluids.
Desperation drives the crew to try every available tactic: hand grenades, gas grenades, and even electrocution—all to no avail as the entity proves immune to conventional weapons. When It is lured into the ship’s atomic reactor room, the crew seals the heavily shielded door and exposes the creature directly to the ship’s nuclear core. It bursts through the door and escapes, the fight moving into a brutal, top-to-bottom struggle as It proves strong enough to tear through the metal hatches between levels.
With survival at stake, the remaining crew members retreat to the control room on the topmost deck, their numbers dwindling and hope fading. Carruthers notes a startling clue: the ship’s oxygen consumption has spiked, likely a sign of the creature’s enhanced lung capacity suited to the thin Martian atmosphere. The plan to outwit the intruder grows ever more ambitious: the crew dons spacesuits, and Carruthers opens the command deck’s hull airlock to the vacuum of space. A catastrophic decompression follows, and the desperate gambit pays off as It suffocates, stranded part way through the final hatch.
In the aftermath, a Earth press conference reveals the truth behind the harrowing voyage. The project director cautions that Earth may now have to bypass Mars entirely, underscoring the planet’s deadly reputation with a stark, memorable line. > "another word for Mars is Death"
