When it comes to mystery and detective fiction I’ll confess I subscribe to the “fair play” doctrine. This is the principle, which some authors make expressly, that the reader gets all the same clues as the detective. What this avoids is a situation where the detective just pulls a rabbit out of a hat at the end, explaining the mystery by way of some evidence that we haven’t been told about. Sure you can still have a great mystery that doesn’t play by these rules, but I appreciate it when the author sets a fair challenge.

Sherlock Holmes seems to have felt the same way, as we learn when he upbraids Watson at the beginning of “The Crooked Man.” It’s a point he makes just after remarking on how Watson has had a busy day. Watson doesn’t know how he managed to deduce this and so Holmes explains:

“I have the advantage of knowing your habits, my dear Watson,” said he. “When your round is a short one you walk, and when it is a long one you use a hansom. As I perceive that your boots, although used, are by no means dirty, I cannot doubt that you are at present busy enough to justify the hansom.”

“Excellent!” I cried.

“Elementary,” said he. “It is one of those instances where the reasoner can produce an effect which seems remarkable to his neighbor, because the latter has missed the one little point which is the basis of the deduction. The same may be said, my dear fellow, for the effect of some of these little sketches of yours, which is entirely meretricious, depending as it does upon your retaining in your own hands some factors in the problem which are never imparted to the reader.”

That said, the effect here is again at least mostly meretricious, as Holmes basically just walks back the events of the night Colonel Barclay dies until he comes to their source in the titular crooked man, who quickly spills the beans. There are red herrings, like the footprints made by a small animal, but little in the way of clues. Even the use of the name “David” is an allusion that ties into an exotic backstory that Holmes had no way of knowing anything about until Harry Wood told him what happened back in India during the days of the Mutiny.

As a bonus, Holmes never says “Elementary, my dear Watson” anywhere in the canon. What he says in the passage quoted above is as close as he ever comes to that famous line. That kind of thing happens more than you might think. Bogart, for example, never says “Play it again, Sam” in Casablanca.

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