The sequel to Storm Over Warlock -- a fact I never knew until many years after I read this one. (I was rather young when that happened.)
It opens on the planet Demeter, where an extremely selective plague took out most of the men -- as if aimed at the government men, and those families who were most supportive of them. A fanatic leader persuaded them to take out the machinery, as well. And Charis, daughter of the education expert, is fleeing from the mob.
Well, they catch her. And she finds them dealing with a semi-legal Free Trader who's selling indefinite term labor contracts, so they can have the agricultural slaves they will need to support the colony, with the men dead and the machinery gone -- and is willing to buy hers. If she's willing to sign instead of being left there.
She ends up on Warlock, where a Free Trader is trying to use her to start trade with the Wyverns. There's another woman there -- quite mad, terrified of the "snakes" -- so she was not his first try. She deduces the existence of a Survey base, and suspecting that the trader is operating illegally, tries to contact them, but before anything comes of it, the Wyverns reach her. They draw her toward the sea, at one point preventing her from contacting a Survey member, but providing food, and when she reaches it, she is welcomed, and they start to teach her.
But a Jack raid leads to more complications, and discoveries. The rest of the book involves her suddenly being cut free as the Wyverns must work together, a creature called a curl-cat, a comparison of native planets, a Wyvern attack being exploited as an escape, and broad discretion being used for an ambassador.