At a time when animals only know myths about the talking humans who once dominated and nearly destroyed the world, a young chipmunk escapes danger in the City of Ruins and, with new friends, finds the Fog Mound, where all creatures live in peace and harmony.

Thelonius the chipmunk, his talking animal friends, and Bill, the tiny human scientist, continue to combat those who would destroy Fog Mound, and even the Earth itself, for personal gain, while learning more truths about the time of the Human Occupation.