The plot begins in the 23rd century, as a United Planets Cruiser arrives at the distant planet Altair IV. Their mission: to investigate the fate of a scientific expedition that landed there two decades earlier and has since gone silent.

The crew, led by Commander Adams, discovers only two survivors: the enigmatic Dr. Morbius and his remarkably beautiful and intelligent daughter, Altaira, who has grown up isolated on the alien world. They are attended by Robby the Robot, an advanced and seemingly indispensable mechanical servant.