Golden Age of Detective Fiction

Introduction

“The Adventure of the Lion’s Mane” is one of the 56 short stories featuring Sherlock Holmes, written by British author Sir Arthur Conan Doyle. First published in The Liberty, an American publication in November 1926, it was later collected as part of The Case-Book of Sherlock Holmes in 1927, the final volume of Holmes stories.

Unusual among the canon, this story is narrated by Sherlock Holmes himself, rather than Dr. Watson, who does not appear in the tale. Holmes as the only narrator only occurs in one other short story “The Adventure of the Blanched Soldier”.

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The Plot

Set after he retired to the Sussex countryside, the tale departs from the familiar London backdrop and Watson’s usual narration, offering a rare glimpse into Holmes’s solo life and methods.

Now retired and enjoying a peaceful life near the sea, Holmes finds himself drawn into a strange mystery when a local schoolmaster, Fitzroy McPherson, collapses and dies near his cottage. His last words—“the lion’s mane”—are cryptic and baffling. What’s more disturbing is the condition of the body: deep red welts streak across his back, as if he had been viciously whipped by some unseen force.

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The Review

Without Dr. Watson at his side, Holmes relies on his own sharp observations and local knowledge. He interviews several of the town’s residents, including McPherson’s colleagues and the enigmatic Maud Bellamy, a beautiful woman with whom the deceased had a romantic connection. Suspicion initially falls on Ian Murdoch, another schoolteacher known for a fierce temper and a previous altercation with McPherson. But Holmes, always cautious about first impressions, digs deeper.

After careful investigation and reflection, Holmes discovers that the killer is not human at all. The “lion’s mane” refers not to an animal or poetic metaphor, but to a Cyanea capillata—a lion’s mane jellyfish, one of the most venomous creatures found in British coastal waters. McPherson had gone for a swim and accidentally encountered the jellyfish, which left the whip-like marks across his back and caused his death from its venom.

This unusual case highlights Holmes’s ability to solve puzzles even when the culprit is nature itself. “The Adventure of the Lion’s Mane” stands out in the Holmes canon for its rural setting, its eerie tone, and its emphasis on deduction over action. Without any villain to bring to justice, Holmes closes the case with quiet satisfaction.

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Final Thoughts

While not as well-known as some of Holmes’s urban escapades, “The Adventure of the Lion’s Mane” offers a unique and atmospheric mystery. With Holmes as the narrator and a rare non-human cause of death, it adds variety to the legendary detective’s final cases and gives readers a glimpse of Holmes in his twilight years—still sharp, still observant, and still the master of deduction.