In a world of talking animals, there is one burning question: did humans ever exist?

Thelonious Chipmunk believes he has proof that they did: a postcard showing a building made of concrete and glass.

But his sister thinks the postcard is just a silly piece of paper - everyone knows humans are only make-believe!

When, one day, a flash flood carries Thelonious away, he wakes up in a strange world that looks something like his postcard, but not quite - it's crumbling and decaying.

If this is proof that humans once existed, where did they go?

Thelonious sets off to find out, and the adventure begins!