En route to a party they are not keen on attending, the Famous Five are almost relieved when Aunt Fanny's car breaks down, stranding them in a small town. To pass the time, they visit the local natural history museum, where some newly-discovered dinosaur bones are being unveiled. Here they meet Marty, who tells them that his father, long dead, supposedly found a complete dinosaur skeleton and made a map of its whereabouts. Unfortunately the map has been stolen. Unable to let a good mystery go unsolved, George, Julian, Dick, Anne and Timmy, join a guided hike through the Valley of Dinosaurs. But their fact-finding mission soon turns into a race to find the dinosaur when they suspect that the thief is one of the group.—Beta Film GmbH

After the five investigators get stuck in a small city because their car breaks down they go to an event where a dinosaur bone that just has been found is presented. After a man (Marty) storms the scene and claims that his father has found the bone, the five investigators go on an adventure to find the place where Martys father found the bone to prove that he is the rightful discoverer. But other people are looking for the dinosaur bones aswell.—Will-Graham