The novel's hero is Diskan Fentress, mutant son of a high-ranking military official who, feeling out of place in a life that requires a certain bearing and poise (he's pitifully overgrown and clumsy), steals a spaceship and runs off to an uncharted world called Mimir to begin a new life. Norton makes the theft of the spaceship ludicrously easy (it amounts to a variation on stealing dad's keys), but clearly Diskan is not the brightest bulb on the tree, either. Crash landing in a frozen, alien wasteland, with barely provisions enough to survive, Diskan soon encounters strange indigenous beings called the brothers-in-fur. Their ancestors, we learn, inhabited a once-magnificent city named Xcothal, the ruins of which poor Diskan soon finds himself led to. There he meets another human, a girl named Julha Than, and a wounded alien called a Zacathan. He learns that the ruins of Xcothal contain a treasure being sought by a band of outlaws called the Jacks.