Stories / The Case-Book of Sherlock Holmes · 1922
The Problem of Thor Bridge
A governess seems damned by a pistol in her wardrobe; a chip on the bridge's parapet and a stone-weighted string prove a suicide built to hang her.
✅ 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 governess, Grace Dunbar, seems doomed by evidence: the wife of her employer found shot dead on Thor Bridge, a note from the governess in the dead woman's hand, and the murder pistol discovered in the governess's own wardrobe.
Holmes distrusts the too-perfect case and studies the bridge parapet, where a fresh chip in the stonework sits low and unexplained. He reconstructs a mechanism: a pistol tied to a weighted cord, fired, then dragged over the parapet into the water below.
The wife, consumed by jealousy, staged her own suicide to hang her rival — pistol on a stone-weighted string that whipped the weapon into the lake, leaving its mate planted in Dunbar's room. The parapet chip proves it; a matching stone is dredged up on Holmes's instruction.
Deeper reading
A suicide built to frame
The Problem of Thor Bridge is among the best of the late canon — a governess doomed by a pistol in her wardrobe, cleared when Holmes reads a chip in the stone parapet and reconstructs a suicide engineered to hang an innocent rival. The stone-weighted gun swinging into the water is one of the canon\'s most elegant physical solutions.
Fair play, admired
Holmes praises the case as one that played fair — every clue available to the attentive — and it is a model of the honest puzzle our Watson\'s Case Files tool is built to help writers construct. Beneath the mechanism is a study of jealousy and despair, giving the ingenuity a human floor.
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Techniques on display
Elimination
Striking out the impossible until the truth remains.
In this story: The framing is undone by a single anomaly: a chip in the parapet no burglar or struggle explains, which only a cord-and-weight suicide-rig can account for.
Deduction & inference
Chaining evidence into conclusions on a living board.
In this story: Holmes reconstructs the weighted-string apparatus from the chip's height and angle, then confirms by dredging the twin stone — physics converting a martyred jealousy into fact.
Fair-play storytelling
Clues planted honestly for readers who play along.
In this story: Holmes praises the case as one a storyteller would prize: a genuine locked-logic puzzle where every clue is available to the attentive — fair play made literal.
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.