When amateur sleuth Jim Qwilleran and his two Siamese detective companions take a trip to the city 'down below' to help save the historic Casablanca apartment building from demolition they find more than they expected. Moving into the penthouse apartment, Qwill, Koko and Yum Yum find a bloodstain under the rug and discover that an art dealer was killed in the very same apartment in which they are living. But with the combined twitching in his salt-and-pepper moustache and Koko's curious whiskers is all what it seems and will the Casablanca be restored in time to it's original glory.....