In ancient times human beings ruled the Earth -- at least that's what the old legends claim. But is it true?

Thelonious Chipmunk is a Talker -- an animal who has inherited the gift of language from his ancestors -- and he, for one, believes in humans. Who else could have made the old paper postcard he treasures? Who else could have built the tall building shown on the postcard? His desire to know more about the humans is fulfilled in a surprising and dangerous way when Thelonious is swept down the river into a strange new world -- a world of architectural ruins and puzzling artifacts, where gangs and warlords prowl amongst the crumbling remains of civilization.

With three new companions -- a bear, a porcupine, and a small brown lizard -- Thelonious embarks on a search for the far-off Fog Mound. It is a journey that becomes nothing less than a quest to uncover the secrets of Earth's past.