Stories / His Last Bow · 1911
The Adventure of the Red Circle
A lodger who never shows a face communicates by candle flashes; Holmes reads the window code and walks into a secret-society vendetta.
✅ Public domain — read, share, and adapt freely.
⚠️ Spoilers below. The analysis discusses the solution, including who did it and how it's found out.
Summary & analysis
A landlady is unnerved by a lodger who never shows a face, communicates by printed notes, and demands meals left at the door; Holmes takes the small mystery of the invisible tenant.
Holmes watches the house and reads a candle flashing at a facing window — signalling in code, letters counted by flashes. The lodger is a woman hidden by her own protector; the flashes spell danger and a name, and a secret-society vendetta closes in.
The Red Circle — an Italian criminal brotherhood — hunts the couple across the Atlantic; a Pinkerton agent and a timely shooting end the pursuer. The unseen lodger's whole ordeal was written in flashes across a courtyard, waiting to be read.
Deeper reading
Signals in the dark
The Red Circle builds a small domestic puzzle — a lodger who never shows her face — into a transatlantic vendetta, decoded through candle-flashes counted into letters across a courtyard. Doyle enjoys the mechanics of covert signalling, and the ordinary boarding house opening onto a secret-society killing is a satisfying widening of scale.
The society that follows you
Behind the case stands the Red Circle, a Neapolitan brotherhood whose reach follows emigrants across the ocean — the canon\'s template for the vendetta that cannot be outrun. An American Pinkerton agent already on the hunt gives the story, like The Valley of Fear, an international law-enforcement dimension.
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Techniques on display
Ciphers & codes
Secret writing broken by frequency and pattern.
In this story: Candle-flash signalling decoded by counting: flashes grouped into letters (one for A, and so on) turn a flickering window into sentences of warning.
Practise: 💃 Dancing Men Cipher Bureau Practise: ⏱️ Cipher Sprint
Observation
Reading occupation, history, and character from visible detail.
In this story: The lodger's habits — printed notes, a woman's cigarette, meals for one — tell Holmes the hidden tenant's sex and situation before she is ever glimpsed.
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.