In the 23rd Century a space ship led by Commander John J. Adams (Leslie Nielsen) heads toward planet Altair-4 in what he thinks is a rescue mission. Twenty years earlier another space ship disappeared on the way to the planet with only one passenger surviving, Dr. Edward Morbius (Walter Pidgeon) who has built up a vast compound from the housing and scientific instruments left from a race called the Krel. All the other humans from the space ship carrying Morbius were killed off by strange vicious animals that the doctor never saw, and only he and his daughter Altaira (Anne Francis) have survived. The previous race had an intelligence far superior to humans and Morbius has harnessed the left-over trappings of the civilization to develop his own research and science. The security of his compound is managed by a robot he has built and named Robby which has the power to replicate any element put inside it so that food and drink are supplied to Morbius and his daughter. After Adams lands his radio is damaged by an unseen force and he suspects Morbius is behind the action but the larger, more sinister force at work on the planet is something no one has imagined and it takes everything Adams can muster to insure he will be able to leave the planet safely.