Stories / The Case-Book of Sherlock Holmes · 1923
The Adventure of the Creeping Man
A professor climbs ivy by night and his own dog attacks him; nine-day cycles and a serum from langur monkeys explain the crawling — science gone vain.
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⚠️ Spoilers below. The analysis discusses the solution, including who did it and how it's found out.
Summary & analysis
A distinguished professor begins to behave strangely — creeping along corridors on all fours by night, his own faithful wolfhound turning on him — and his daughter fears his mind is going.
Holmes charts the fits and finds they recur on a nine-day cycle; a mysterious foreign correspondence and small packages align with the dates. The professor, infatuated with a young fiancée, has been injecting a rejuvenation serum derived from a langur monkey.
The serum lent him a langur's agility and instincts — hence the climbing and the dog's revulsion — and would have destroyed him. The cycle was the dosage schedule; Holmes reads a calendar of symptoms back to a syringe, and warns that such vanity endangers the species.
Deeper reading
Science fiction in the canon
The Creeping Man edges into science fiction: an ageing professor injects a monkey-gland serum to regain youth and begins to move and behave like an ape. Doyle uses a nine-day behavioural cycle as the clue, and the story reads as a fable about the folly of unnatural rejuvenation — a late, strange, cautionary tale.
A warning dressed as a mystery
Holmes\'s closing reflection — that such tampering with nature invites disaster — gives the story an unusually explicit moral. It is minor and eccentric, but its unease about science overreaching itself feels oddly modern, and it stands apart from the realistic detection of the classic cases.
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Techniques on display
Chronology
Laying events end to end until contradictions die.
In this story: The nine-day rhythm is the master clue: symptoms recurring on a fixed cycle mean a scheduled cause, and matching the dates to the parcels finds the injections.
Observation
Reading occupation, history, and character from visible detail.
In this story: The dog's dated hostility and the knuckle-marks on the ivy are physical evidence that the man had, at intervals, become something animal — read before the serum is named.
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.