The Crown Diamond is a one-act Sherlock Holmes stage play written by Arthur Conan Doyle, later expanded into the short story "The Adventure of the Mazarin Stone." In this compact drama, Holmes attempts to recover a spectacular stolen diamond (part of the Crown Jewels) from an aristocratic thief in a single evening. The action unfolds in one room where Holmes employs a daring ruse: using a wax dummy of himself to draw out the culprits while he eavesdrops in disguise nearby. Taut and clever, the play is rich with Holmes's signature deductive tricks – from secret listening devices to bold confrontation – all within about twenty minutes of stage time. Dr. Watson and Inspector Lestrade have supporting roles, mostly marveling at Holmes's theatrics. The Crown Diamond offers a crystalized dose of Holmesian suspense and ingenuity, written specifically for the theater. Doyle's playful use of a dummy to deceive villains gives the audience the delightful experience of outwitting criminals alongside the Great Detective.