The cat who went into the closet - Lilian Jackson Braun

Jim Qwilleran and his sleuthing Siamese companions, Koko and Yum Yum, up sticks from their converted apple-barn home for the snowy winter months and move into the old Gage mansion. The house belongs to Junior Goodwinter's grandma, Euphonia, and is full of commonplace treasures hidden in dusty closets - a curious cat's heaven. Everything goes well until the phone rings announcing that Euphonia has been found dead at her new Florida home. The strange thing is that the apparently happy and healthy 88-year-old seems to have committed suicide.