Dragon Quest ~ Anne McCaffrey

This is the second book in the Pern series. It has been several years since Lessa went back in time to bring forward the wyers of dragons to fight thread. Now there are troubles with those dragonmen. They are having a hard time adjusting to modern times and practices. And on top of that, even more seems to be changing, and Thread is not keeping to the pattern that had been worked out. Now F'lar and Lessa need to determine what must be done now.