Investigating the disappearance of a second Pegasus rocket, American astronaut Capt. Frank Chapman is forced to land his spaceship on Rehton, a mysterious asteroid. Upon opening his space suit he is reduced in size by the atmospheric conditions and captured by a race of tiny people, ruled by Sesom. Liara, Sesom's daughter, is attracted to Chapman, but he becomes attached to Zetha, a mute. After befriending the jealous Herron, Liara's admirer, Chapman wins the respect of the Rehtons. The astronaut helps the tiny kingdom defend itself when unexpectedly attacked by the Solarites, an ancient enemy. Zetha, rescued by Chapman when she is abducted by a Solarite, regains her speech in the excitement. Donning his space suit, Chapman regains his normal size and returns to earth, realizing that his experiences on Rehton will not be believed.