Epic fantasy about a group of super-intelligent cats. Rhiow appears to be a pampered New York pet cat, but in reality she is a wizard, working alongside human beings and other animals to protect the world from the forces of darkness, which are attacking the city via the underground tunnels.

The wizard cats Rhiow, Urruah, and Arhu are summoned to London to deal with a crisis that could destroy the very fabric of time, and they join forces with a teenage Arthur Conan Doyle to stop the evil schemes of their old nemesis, the Lone One.