For cavemouse Geronimo Stiltonoot, life is one prehistoric problem after another! 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!