A caveman named Spear returns from a fishing trip to find his mate, son, and daughter devoured by a trio of red, horned Tyrannosaurs. Distraught, he contemplates suicide before resolving to take revenge. He sees the silhouette of a dinosaur. Believing it to be one of the horned tyrannosaurs that killed his family, Spear silently pursues it into a thicket, instead seeing it is a blue Tyrannosaurus rex named Fang, with two offspring with her. Spear realizes his mistake and befriends the offspring