Set in the 23rd century, the United Planets starship C-57D arrives at Altair IV to investigate the fate of the Bellerophon, a mission that vanished two decades earlier. Upon arrival, Commander John J. Adams and his crew encounter Dr. Edward Morbius, the sole survivor, who warns them against landing due to an unseen danger. Despite the warning, they proceed and meet Morbius's daughter, Altaira, and Robby the Robot, a sophisticated automaton.