Emma Vernon lives on a lake in the Adirondack Forest Preserve with her husband, Max, and their cat Billie, Animals belonging to species thought to have become extinct ten thousand years ago – woolly mammoths, sabertooth cats, giant deer – suddenly appear along the shore.
Bewildered and extremely dangerous, the oversize beasts invade the town, frightening its residents. Billie finds the portal through which the animals are entering the present. Together, Billie and Emma gain an understanding of the animals’ relationship with the primitive humans of their original era. The story is told through Billie’s eyes as well as Emma’s.