Sam Knowlen, dutiful student and son, almost eighteen and searching for his perfect mate, runs afoul of a witch named Leena one night while taking in the nightlife of Tacoma, Washington. Leena, a spiteful individual, mistakes Sam for her familiar, and in a drunken rage, uses her magic to change Sam into a cat. She then vanishes from sight.

Sam is on his own and has to navigate life as a feline, putting up with being petted by some, kicked around by others, and shunned by his mother. In his travels, he meets Holly, a white rat who also ran afoul of Leena, and together, they try to find Leena and somehow convince her to change them back.

Along the way, they meet Magros, a sadistic imp who is Leena's true familiar and who tries to kill them, Angelo, a massive cat-gangster who has his own agenda in mind, and a veterinarian who wants to sell them as potential spies to the army.

Finding kind as well as cruel people, Sam and Holly eventually find Leena which results in a showdown that only one side can win.