Fans of McCaffrey's (The Chronicles of Pern, 1993, etc.) famous dragons will no doubt be surprised by this latest installment in the Pern saga, which, for a change, spotlights the planet's dolphins. Although genetically engineered dolphins were part of the original Pern colony, humans lost contact -- and interest -- in the friendly cetaceans over the years, as they desperately developed the fire-breathing dragons to combat the deadly thread. But when a pod of dolphins rescues young Readis and his Uncle Alemi from a storm, the pair is stunned into silence by the appearance of the legendary talking ""ship fish."" While few back at the holding believe the pair, Aivas (an ancient computer) encourages the contact. The dolphin's gentle (and too often cutesy) nature eventually wins over the other humans, including young T'lion, a dragonrider. While the residents of Pern launch a bold plan to rid their planet of threadfall forever, T'lion and Readis realize that it is their destiny to work with the dolphins, like the dragonriders who worked with the winged flyers before them. McCaffrey's solid characterizations and lush descriptions counterbalance the feathery plot, making this latest trip to Pern a pleasant, sentimental respite among old and familiar friends.