It! The Terror From Beyond Space (1958)

IT! THE TERROR FROM BEYOND SPACE 
    D: Edward L. Cahn                      (1958)  ¢ ¢ 1/2
    Marshall Thompson, Shawn Smith, Kim Spalding,
    Ann Doran, Dabbs Greer, Ray Corrigan
B-movie hero Marshall Thompson plays an American astronaut, the only survivor of an ill-fated voyage to Mars. Sketchy circumstantial evidence suggests he murdered the rest of the crew, and a second ship is dispatched to bring him back to Earth for a court-martial. The mystery of whether he done it gets resolved pretty quickly on the return trip home, and it just as quickly becomes clear that there's a monster aboard, killing off the space travelers one by one. This is the kind of '50s sci-fi thriller in which the inside of the spacecraft is roughly the size of a warehouse, and guns and grenades can be used against the monster without doing any structural damage to the ship. It's one of the movies that turned up on TV a lot when I was a teenager, and its shortcomings were obvious even then, which of course didn't prevent us from watching it over and over again. The guys who would dream up "Alien" 20 years later must've been watching it, too, back then, taking notes.