Harry thinks he's too old for his bucketful of dinosaurs but they have other ideas. He looked after them when he was little and now they're determined to stick by him . . . for life. And Harry is not the only one who's got a lot bigger! When a mysterious set of plastic dinosaur cards appear on his key-ring, Harry soon finds that he can call on an army of Back-Up Dinosaurs. It only takes a rub with his finger to call up some MONSTER-sized muscle! When a big snow storm blocks the roads, the residents of Huntingdon village are trapped. Harry and his friends - Jack, Charlie and Siri - want to deliver emergency supplies. But it would take the strength of a triceratops or the enormous bulk of an apatosaurus to help them . . .