All the mammoths have fled Old Mouse City! It's a total cat-astrophe! Not only because mammoths are valuable allies of the cavemice, but also because without them, the cavemice can't make mammoth milkshakes, their delicious national drink. Geronimo Stiltonoot must embark on a daring journey to find the mammoths...and avoid going extinct before he gets back!

Kip the Cave Boy and Paleowolf each face hunger and danger on a journey in Paleolithic times, and when they decide to join forces and help one another, Paleowolf becomes the first dog.

After encountering a variety of animals in his search for a warm place, a boy living in prehistoric times returns to the warmth of his parents' cave.