An astronomer, harnessing telescopes located on the far side of the moon, made an astonishing discovery: there is a planet that lies beyond Pluto! Starlight Enterprise decided to send an expedition to explore the planet Nyx, and the Starman trio are going along. Trouble begins almost at once: the ship jointly built by Nolan Mining Enterprises and Starlight Enterprises experiences near catastrophic failure midway to the planet. What's worse, a spirit of fear begins creeping upon the crew: rumors abound that the planet Nyx is a planet of doom. When the ship lands, the Starmen take a shuttlecraft down to the surface to explore - and when they return they find their ship was gone! Events soon throw the Starmen into a desperate conflict with an ancient extraterrestrial menace, and the only weapon the Starmen have is their own courage. The Starmen must battle not only alien foes, but desperate human foes as well as they fight for life on the Planet of Darkness.