Science teacher John Butler (Mike Road) embarks on an expedition and it turns into a trip that he and his family will never forget. John is joined on the trip by his wife Kim (Shannon Farnon), children Katie (Kathy Gori) and Greg (Jackie Earle Haley), and their dog Digger (Frank Welker). While rafting down the Amazon, their boat hits a rock and capsizes. They are then sucked into a whirlpool which pulls them through an underground cavern. They resurface and find that they’re in a strange prehistoric valley — complete with cave dwellers and dinosaurs. They meet caveman Gorok (Alan Oppenheimer) and become friends with him and his family. Gorok’s mate is Gara (Joan Gardner) and their two children are Lok (Frank Welker) and Tana (Melanie Baker). They also have a pet, a dinosaur named Glump (Frank Welker). Narrated by Don Messick, the series shows the two families working together with Gorok and his kin helping the Butlers try to find a way home while learning how to survive in the strange valley.