"Blue Carbuncle" is a short story by Arthur Conan Doyle featuring the famous detective Sherlock Holmes. The narrative revolves around a lost gemstone, a blue carbuncle, that is discovered inside a goose. Holmes is approached by a man who found the goose and wants to return it to its owner, leading to an investigation that uncovers a series of events tied to the gem. The story highlights themes of morality and justice, as Holmes navigates the complexities of human nature. It showcases his keen observational skills and deductive reasoning, ultimately revealing the true owner of the blue carbuncle and the circumstances surrounding its loss.