Nib lives deep beneath the city, in a subway station the mice call Sweetfall. By day, the trains thunder past. At night, the old mice tell stories of the mythical land known as Tunnel's End, where the air is sweet and the nests are soft, but where scary, mouse-eating monsters roam. One day, Nib sets out on a quest to find Tunnel's End. Along the way he faces danger, finds a friend . . . and discovers a place more wonderful than he ever dreamed.