Tom Merriam (Russell Wade) boards the freighter Altair in San Pedro, where he meets Capt. Will Stone (Richard Dix). During that first voyage, Tom begins to suspect that Stone is crazy, but he also learns that the crew is fiercely protective of him. When fellow sailor Louie (Lawrence Tierney) is killed in a freak accident, Merriam suspects Stone. However, he has no proof. As the killings continue, Tom decides to leave the ship, but the captain has other plans.