The story of King Bertram of Binn, who dedicates himself to safeguarding his kingdom, which has a precarious existence. It is surrounded by water, which is held back from flooding the land by a ring of dike trees, which are in turn subject to attack from flocks of nizzards. To protect the kingdom, a legion of Patrol Cats is organized to keep the nizzards at bay, and King Bertram sees to their care personally.