Geronimo Stilton surprisingly enters into the unknown world and finds himself in a times machine. Meanwhile he accepts the invitation of Professor Von Volt and reaches the world of past. Geronimo goes back to the Jurassic age where he discovers dinosaurs and realizes they are getting destroyed. He was very happy in this world of fantasy and was enjoying till the time he finds himself being stalked by a tyrannosaurus-rex, who had been wounded by a crocodile in the blue river Nile. what happens after that???