In the end of The Three Gables, the woman responsible for the trouble in the story asks Sherlock Holmes for help.
“Well, well,” said he, “I suppose I shall have to compound a felony as usual.”
It’s an interesting phrase, because it’s true—Holmes does often let the criminal go. I was reminded of this when I recently re-watched the Jeremy Brett version of The Priory School, and then re-read the short story to see the differences. Perhaps the biggest change is that in Conan Doyle’s version, Holmes lets the criminals off, while in the Jeremy Brett version there’s one fewer criminal, and the main criminal ends up falling to his death rather than being let off. (To be fair, in the Conan Doyle version, the actual murderer does get caught and is said to be almost certain to hang for the murder.)
This is a rather curious trend. Though the Holmes stories in large part launched the genre of detective stories, in many ways they frequently bucked the trends that quickly came to dominate the genre.
Holmes stories do not tend to feature fair play; in fact they often almost pointedly eschew it with Holmes seeing some evidence which he refuses to show to Watson. The Priory School has an example of this; Holmes stands on Watson’s shoulders to see who is holding the young boy who was kidnapped, but Watson doesn’t get to see who it was and only learns it when Holmes accuses the man.
Holmes stories are frequently not about murder, though admittedly even in the golden age not every mystery story was about murder. I can think of at least three Father Brown stories off of the top of my head which were not. That said, in Holmes stories murder is probably more the exception than the rule.
But perhaps nowhere do Holmes stories buck the trends of the genre they started so much as in how often Holmes lets the criminal off. It’s not merely occasional, it’s all over the place. Perhaps the most memorable instance of it is in the end of The Blue Carbuncle:
“After all, Watson,” said Holmes, reaching up his hand for his clay pipe, “I am not retained by the police to supply their deficiencies. If Horner were in danger it would be another thing; but this fellow will not appear against him, and the case must collapse. I suppose that I am commuting a felony, but it is just possible that I am saving a soul. This fellow will not go wrong again; he is too terribly frightened. Send him to jail now, and you make him a jail-bird for life. Besides, it is the season of forgiveness. Chance has put in our way a most singular and whimsical problem, and its solution is its own reward.
Perhaps it’s the second bucking of the trend which is so often responsible for the first; I can’t think of any case where Holmes lets a murderer go. (I should note that my knowledge of his cases is not encyclopedic. That said, I think that in later stories the preference in both readers and writers developed for the detection in detective stories to have some purpose, that is, to have some effect. It need not be a legal effect, of course, though it commonly was that. The solution should please more than just the detective; it should reconcile people to each other or give someone peace.
There are no hard and fast rules on this, of course. I’m quite fond of the Poirot story Murder on the Orient Express, where Poirot lets the killers off. It’s actually more complicated than that; he does not make the decision at all. The director of the Wagon-Lit company that runs the orient express asked him to investigate and he did. He then presented to the director two possibilities. The first was of an assassin who snuck out through a window when he was done. The director dismisses, but Poirot warns him not to dismiss it so quickly. After he hears the second explanation, he may not think so badly of this one. He then explains what really happened, where the death was, basically, the execution of a foul murderer of an innocent child, who had heretofore escaped justice. When he fully understood what had happened, the director did indeed prefer the first explanation, and it was what was given to the police when they eventually arrived. There was a cathartic effect to the action, though, where an impartial judge was given to judge the case, and pardoned the killers. The detective, effectively, reconciled the killers with society.
I am, in fact, fond of the surprise ending where the detective lets the killer go because he is not really a murderer. I suppose I just think that it should be a rare exception for it to have its real effect.
Ultimately, though, it is right that the detective cares more for justice than for the law, and it is generally best when the detectives are not retained by the police to supply their deficiencies.