Stories / The Case-Book of Sherlock Holmes · 1921
The Adventure of the Mazarin Stone
A crown diamond, a wax dummy in the window again, and a gramophone playing violin: the thieves hand Holmes the stone while talking themselves into prison.
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⚠️ Spoilers below. The analysis discusses the solution, including who did it and how it's found out.
Summary & analysis
The Crown's great yellow diamond, the Mazarin stone, is stolen; Holmes, watched and threatened, sets a trap in his own rooms using a wax dummy of himself at the window and a gramophone playing his violin.
Told almost as a stage play, the story is a confidence duel: Holmes shuttles between his real self and the dummy, letting the thieves believe him occupied while he stands among them in disguise, and manoeuvres the pair into discussing where the stone is hidden.
Convinced Holmes is fiddling next door, the thief slips the diamond from his pocket into what he thinks is a safe hand — Holmes's own — and talks himself into custody. The bust and the record do the detecting; the reasoning is all in the staging.
Deeper reading
A story built like a play
The Mazarin Stone is adapted from a stage sketch, and it shows — confined almost entirely to the Baker Street sitting room, told in the third person, and reliant on a single theatrical device. Doyle recovers the jewel through pure stagecraft: a wax dummy of Holmes at the window and a gramophone violin to convince the thieves he is elsewhere.
Minor Holmes, clever trick
It is among the slighter tales, and Watson is oddly sidelined, but the central conceit — the criminal slipping the diamond into the detective\'s own hand while boasting himself into custody — has a neat comic economy. It reads as what it is: a filmed magic trick transcribed to the page.
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Techniques on display
Disguise & misdirection
Seeing through appearances built to deceive.
In this story: The wax bust returns, paired with a gramophone violin, to manufacture a Holmes who is elsewhere — freeing the real one to stand disguised among his hunters.
Practise: 🚨 Lestrade's Lineup Practise: 👁️ The Science of Deduction
Interrogation & deception
Testing stories for the thread that doesn't reach the wall.
In this story: Holmes lets the thieves incriminate themselves by feeling unobserved: the whole trap is engineered candour, a confession extracted by staged absence.
Practise what this story preaches: every technique above links to a tool or game built on the same method. The best way to learn the canon is to reason along with it.