Fen and his Clan, the Purgies, are a group of small mammals that live in the hostile and hauntingly beautiful world of the dinosaurs of the Late Cretaceous Era. They live in a remote mountain valley beside a life-giving river where dinosaurs rarely come. The clan of Purgies have prospered in their home of Burrow Mound for generations. But a secret attack from the Raptorlike Sinosaur sends their world into turmoil. With the sudden arrival and mysterious warning from one of the greatest dinosaurs of all, the T-Rex, Fen and his people are set on a harrowing course of survival and adventure that leads them through their fantastic world and on a date with destiny that started 65 million years ago...and may end with us.