ISFDB lists 1980’s Zelde M’Tana as the third book in the Rissa Kerguelen series. Even though it was the last of the Kerguelen series to be published, it is not a sequel at all. It’s a prequel. Rissa doesn’t appear in this book; her man-candy Bran Tregare appears only towards the end. This novel focuses on the eponymous Zelde and her life before she crossed paths with Rissa.
When we first meet her, Zelde does not seem a likely candidate for star travel. She is one of North America’s Wild Children, with little memory of her long-lost parents or any other way of life; she’s only mostly sure that her name really is Zelde M’Tana. Zelde is snatched up by Rehabilitation, an agency with a do-good name and some do-bad methods and goals. After Zelde attacks a Rehab officer, she is scheduled for a lobotomy and life in the slave camps of Total Welfare.
Luckily for Zelde, there is such a thing as a kind-hearted Rehabilitation officer, who sees her as someone worth salvaging. Zelde is diverted to the UET (United Energy and Transport) starship Great Khan , the first step towards to what the official hopes will be a better life out in the stars. “Better” is a relative term: she is being exported as a sex slave, to a brothel on the distant mining colony Iron Hat.
But Great Khan will never reach Iron Hat.