Mo is a little girl who lives with her family in the Stone Age, and her main task is to keep an eye on baby Babba - a fast crawler. Up on the hill she has a secret den of her own and one day she hears something odd, a 'Yip' coming from a bush. It's a small wild beast.

Mo knows that wild beasts are dangerous, but this one is in trouble, with a thorn in its paw. Brave Mo takes out the thorn and the little beast becomes her friend. But Mo's family are horrified by the strange creature. They scare it away and in the excitement baby Babba disappears.

Then they hear a "Woof! Woof!" Oh no! But it's not what they think - Mo's friend is defending Babba from a hungry lynx. From then on the whole Stone Age family has a new friend, and they decide to call it - DOG.

This story is inspired by the astonishing recent discoveries in the famous Chauvet Cave in France's Ardèche department. The footprint of a young child has been discovered, with what is believed to be the paw-print of a dog beside it. They are from 26,000 years ago.