Notes
The Door Through Space, a Darkover novel by Marion Zimmer Bradley.

First published by Ace Books in 1961.

Strictly spreaking not part of the Darkover series, but Darkover is mentioned in passing (as another planet) and many Darkover elements appear (red sun, Dry Towns with chained women, catmen and other non-humans, Terran Empire trade cities, Ghost Wind, etc).

Publisher’s Blurb – Lower Cover
The Terran Empire maintains its sovereignty across half a galaxy – with the consent of the governed. It is a peaceful reign, maintained by agreement and not by conquest. If anarchy ever threatens, law and order in the Empire is kept by the mind-power of a handful of men.

RACE CARGILL is one of those men – a member of the Terran Secret Service. Because of them there has never been open war . . . yet.