Madame Adelaide Bonfamille is a retired opera singer who lives in Paris, France. Knowing that she is growing older, she calls on her attorney, Georges Hautecourt, to draft her will. In it, she lists her four cats, Duchess and her three kittens, Berlioz, Marie, and Tolouse, as her sole beneficiaries, naming her butler, Edgar Balthazar, as a beneficiary once the cats have lived their full lives.
Unbeknownst to her, Edgar overhears this and takes issue with her decision. He steals away the cats in the night, leaving Bonfamille to believe that the cats have somehow been lost.
She lives in a state of sadness until she hears them upon her doorstep. Before she can discover the returned cats, though, Edgar hides them in a sack.
Once the cats have been freed, thanks to Tom O'Malley and his fellow alley cats, among others, Bonfamille adopts Tom and alters her will once more, writing out the now missing Edgar, and dedicating her funds toward a new foundation to care for the stray cats of Paris.