In the future world of 1980 the United States Air Force’s Space Exploration Wing has bases on the moon and is on the eve of a mission to Mars. When one of their Pegasus spacecraft with two crew members aboard mysteriously disappears, Mars mission pilot Captain Frank Chapman and his navigator Lt. Ray Makonnen are sent to search for them in their own Pegasus craft. During their search their ship receives minor damage from a meteor shower that both men go outside to repair. However, a small bullet sized particle pierces Chapman’s suit that sends him into unconsciousness. Makonnen is able to repair Chapman’s suit but as he opens the door to push Chapman inside he is fatally struck by a similar particle. Makonnen’s last act before he is propelled into deep space is to close the door with Chapman safely inside the ship. Chapman awakes to find Makonnen gone and unable to communicate with the lunar base. He leaves a diary message of the preceding events concluding that he is going to land on an asteroid that has somehow pulled his ship in to it. Exiting his ship but still feeling the effects of his unconsciousness, he passes out and sees small humans about six inches in size approaching him. Once the visor of his helmet is opened, Chapman is able to breath but due to the planet’s unusual atmosphere, he is also shrunk to six inches in size. He is placed on trial for attacking Herron, one of the small people. Sesom, the leader of Rheton, the name of the planetoid that Chapman has landed on, explains that though he will have all the rights of an inhabitant of Rheton, he can never leave and his ship has been sent back into space whilst he slept. Sesom explains that though his craft was brought safely down by their tractor beam the preceding craft wasn’t and was destroyed with its crew in a crash. Chapman meets two beautiful women Liara and the mute Zetha who welcome him and answer his many questions. Sesom informs Chapman that he may choose one of the women to marry. Liara, after following and engaging constantly with Chapman, declares her love for him, but is turned down by Chapman. Meanwhile, Herron, who is in love with Liara, in an attempt to win Liara for himself, tells Sesom that Chapman is unfairly attempting to win the favors of both the women. Stating that he believes this to be a crime against the people of Rheton, Herron requests a fight to the death with Chapman. Chapman agrees, and the two engage in a form of combat where opponents must push each other onto gravity plates that cause immediate disintegration if touched. Just as Chapman is about to push Herron onto a plate, he lets Herron go, stating that he cannot kill someone for no good reason. Chapman and Zetha become more acquainted as time goes on and eventually fall in love. Herron comes to Chapman and tells him he can help him escape. However, a Solarite, a member of a deadly alien race, who has been imprisoned on Rheton escapes and captures Zetha in her sleep. Chapman and Herron attempt to rescue Zetha, and Chapman defeats the Solarite. While being kidnapped, Zetha is scared out of muteness and can speak again, confessing her love for Chapman. The two kiss, but they are interrupted as it is revealed that a search party from Earth had located Chapman. Chapman reluctantly heads back to Earth with the search party, leaving Rheton and Zetha behind.
