In this family-friendly holiday mystery, Sherlock Holmes is asked to discover the identity of a man who lost his hat and goose in a late-night scuffle. At first, Holmes treats the request as only a mild curiosity, but then the countess of Morcar's rare and valuable blue carbuncle is found stuffed down the goose's throat. The pursuit of the thief leads Sherlock Holmes and Dr. Watson from 221B Baker Street to Covent Garden Market and all over the streets of wintry London.