In the 23rd century, the United Planets starship C-57D reaches the distant planet Altair IV to determine the fate of an Earth expedition sent there 20 years earlier. Dr. Edward Morbius, one of the expedition's scientists, warns the relief ship not to land, saying he cannot guarantee their safety, but C-57D Commander John J. Adams ignores his warning. After landing, Adams and Lieutenants Jerry Farman and "Doc" Ostrow are met by Robby the Robot, who transports them to Morbius' residence. Morbius describes how, one by one, the rest of the expedition was killed by a "planetary force" and that their starship, the Bellerophon, was vaporized as the last survivors tried to lift off. Only Morbius, his wife (who later died of natural causes), and their daughter Altaira were somehow immune. Morbius offers to help them prepare to return home, but Adams says he must await further instructions from Earth.