For cavemouse Geronimo Stiltonoot, life is one prehistoric problem after another! It's the start of an exciting cavemice contest: a race to Boulder Bay and back! It's a dangerous route, but it will supply the village cheese maker with rare hot lava peppers, and there's a big cash prize. Trap teams up with Geronimo -- who has a lazy, slow, city autosaurus (the cavemice mode of transportation). Can they reach the finish line without going extinct on the way?