Alerted that classified files on a superweapon have been stolen, the Time Lords send the newly Earth-exiled Doctor and his companion Jo Grant to the frontier world of Uxarieus, where a struggling human colony is under pressure to abandon its claim. Two settlers are found dead in what looks like an animal attack, but the Doctor suspects the truth is closer to home, and an official sent to arbitrate the colony's land dispute with a mining company may not be who he claims. Malcolm Hulke's 1974 novelisation of the Third Doctor serial Colony in Space, the first story to send the exiled Doctor off Earth.
Summary by Loreful, from public sources