All the rodents in New Mouse City are at the Rodeon Cinema, waiting to watch the new thriller on dinosaurs by Creepella Von Cacklefur. The movie starts, but suddenly the screen rips open and . . . real dinosaurs emerge! So Operation Dinosaur-Busters starts, in which the Stiltons want to capture the “beasts” to send them back in time, thanks to a Time Machine invented by Nosygenius. During the mission, Geronimo and Nosygenius realize that Shadow, the ally of the evil Madame No, is going around the city with a huge dinosaur egg. He got it directly from the past to make it the new attraction at Madame No’s big Prehistory Park, but in doing so he damaged the Time Machine, bringing all the dinosaurs into the present. Fortunately, Operation Dinosaur-Buster works. Moreover, Geronimo and Nosygenius manage to recover the triceratops egg from Madame No’s mansion and replace it with one made of papier-mâché. Now all they need to do is bring it back to the Cretaceous and then go to the Jurassic to bring home Splinter, a little stegosaurus that Trap wanted to keep for himself. This is the beginning of an enthralling adventure for our friends, who aboard the C.R.O.S.T.A., a prototype of a Time Robot, will first go to the Ice Age by mistake, then to the Cretaceous and, finally, the Jurassic, where they will complete their mission.