Miss Leticia Rabbit leaves her gold necklace on the grass outside her house one evening. When she gets up in the morning, it is gone! To help her get it back, she asks Sherlock Ferret, who lives with his well-whiskered friend Watson Mouse M.D. (a Doctor of Mousology) in rooms under Mrs. Hudson's baker's shop. Sherlock and Watson, and their friend Lestrade, who is a rhinoceros (even though he is not a very big one) set out to find the necklace for her, meeting several interesting and nefarious characters, such as Moriarty Magpie, and the frightening Colonel Sebastian Moorhen as they do so.