Having read a fair number of Agatha Christie mysteries lately, and especially thinking about her earlier mysteries, has led me to think about ingenious murders and the related subject of ingenious plots of murder mysteries. Agatha Christie was, I think, the queen of outwitting the reader. Certainly, she broke more of Fr. Knox’s rules in a way that forced him to amend the rules than anyone else I know of. This was a trait that was much appreciated in her day, and I think still is, though I suspect less so now. Which leads me to ask how important it really is.

The main thing, it seems to me, that a really ingenious murder gives a story is the ability to present all of the evidence up front and maintain an air of mystification among the characters while keeping them reasonably intelligent. It also, of course, makes for a very satisfying reveal at the end of the story.

Of course, if this is not done well—if, for example, the solution is obvious—it makes for a particularly uninteresting murder mystery in which all of the characters seem to be idiots. The best example I can think of this is The Benson Murder Case by S. S. Van Dine. It was extremely obvious that the brother of the victim had killed him, and the entire rest of the novel until the last chapter was uninteresting filler because it obviously bore no relationship to the characters figuring out whodunnit. Worse, Philo Vance (the detective) already knew that it was the brother, too, so he was fairly explicit that he was wasting everyone’s time. The Benson Murder Case is a book that I cannot recommend too little. If you ever have the opportunity to not read it, I strongly suggest you take it.

The downside to the clever murder with the facts set out early—when it’s done well—is that re-reads have a very hard time being satisfying. This is not necessarily a problem for most people, but I prefer to read, as far as possible, only books that are worth re-reading. On this score, murder mysteries were the detective must find evidence, which leads him to the next evidence to find, etc. tend to have significant advantages.

This can be ameliorated, however, by the introduction of red herrings which require additional evidence to eliminate. If done well, the red herrings, prior to elimination, make the solution possible but improbable. Once the red herrings are gone, we get to Sherlock Holmes’ famous dictum that once you have eliminated the impossible, whatever remains, however improbable, must be the case. This, I think, tends to be far more satisfying on re-reading because the work is necessary and not merely killing time until the detective realizes the true solution.

Perhaps the best example I can think of this is my favorite Cadfael novel, Saint Peter’s Fair. (spoilers ahead.)

Once the killer of Ewan of Shotwick is found out to be Euald, on top of Turstan Fowler having given evidence against Philip Corviser and having been found by Ivo, drunk but suspiciously recovered in the morning—it is possible to guess that Ivo was responsible and Euald and Turstan were acting under his orders, but it was by no means probable. It took more evidence for Cadfael and Hugh Beringar to see Ivo’s evil as really possible. The getting of this evidence by Philip, which foreclosed other possibilities, was very helpful, and in consequence it’s one of the great things to re-read in the novel each time I do.