Imagine it: years from now, you’ll be able to say to your descendants “I was there, I remember well the day Jim finally completed his rule-by-rule examination of the Knox Decalogue“.

Here are the links to everything:

And, one last time, here’s a rule in full so we know what we’re talking about; lawks, I feel quite emotional:

Twin brothers, and doubles generally, must not appear unless we have been duly prepared for them. The dodge is too easy, and the supposition too improbable. I would add as a rider, that no criminal should be credited with exceptional powers of disguise unless we have had fair warning that he or she was accustomed to making up for the stage. How admirably is this indicated, for example, in Trent’s Last Case!

The “dodge” to which Knox is referring must be more than simply the presence of identical twins or doppelgangers — odd indeed would be the detective novel featuring identical twins who in no way seek to exploit their similarity of appearance — so we’re talking here about the old “someone in two places at once” ruse. Were a novel to exist, for instance, in which a man under lock, key, and observation in jail overnight also appears on he other side of town, and the explanation for this given in the elucidation was “Oh, and of course he had a twin brother…”, this is the dodge to which Knox refers. In many ways, I’d suggest this is merely a refinement of one element of rule 8 about declaration of clues: the declaration of a twin is, you can bet your house, a clue that said twin will probably appear at some later point. Chekov’s Twin, if you will.

The difficulty is that Chekov’s Twin is, like that casual mention of some acting experience someone had in their teens or the circus they ran away to join for six months after university, something of a klaxon; as soon as they are mentioned, you know to keep an eye out for them. For the purposes of surprise, then, it is understandable that writers may be reluctant to declare this, since it’s difficult to drop into conversation casually — and any attempt at circumlocution to introduce the idea is likely to be as clumsy as those scenes in which a first-person narrator looks in a mirror and describes their own features so that we, the reader, know what they look like. This is not to say that the principle of twins and doubles can’t be used well, just that it needs some careful handling.

So, what are the good examples? Well, that might be a spoilers, but I can offer some broad strokes in some non-Golden Age works. There is a novel not reviewed on this blog by occasionally mentioned in glowing terms by this reader in which the existence of twins is known from the off but, due to a cunningly subtle piece of placement, the fact that they are non-identical twins of different genders is both heavily hinted at and yet also left obscure. And a superb reversal of the identical twin trope can be found in the Jonathan Creek episode ‘Time Waits for Norman’ (1998) in which a man is eating lunch in a fast food restaurant in England while simultaneously being killed (at a firework display, if memory serves…) in the US. One entry in a beloved series enables the mystery to remain obscure because similar-looking brothers live at similar-sounding addresses (32 Beechwood Road and 32 Backwoods Road, say), which is a neat way to double up on the nature of doubledom. It’s not a good book, but the use of the concept is at least a little more inventive than what one usually encounters.

An egregiously poor use of the trope can be found in Andrew Mayne’s so-slapdash-it-beggars-belief Angel Killer (2014) in which — oh, spoilers if you care — a lost WW2 plane is found with its pilot perfectly intact because the killer was able to find a man who looked identical to the pilot, convince him to leave the country in a way that would raise no suspicions, and then after putting his dead body in the plane replace the record of the original pilot’s fingerprints with those of the newly-dead man (how most of this is accomplished is never explained). There’s an impossible crime short story in one of those Mike Ashley-edited collections in which a dead man is seen committing a robbery because the criminal has the means to project an exact likeness of someone else’s face over their own, despite their being no hint that such technology might exist in whatever version of reality that story inhabits. And Agatha Christie cannot go unmentioned, if only for the book in which someone dresses up as their cousin dressing up as a third person and even manages to make their handwriting look as if this cousin had faked the third person’s penmanship.

It’s this overburdening of convenience and shorcuts on top of what is already a fairly thin series of likelihoods that induces a sort of torpor on the detective fiction reader. As a fan of the impossible crime, I’m happy to accept that certain unlikely physical acts can be pulled off if only because it’s on account of these events happening that the impossibility comes about, but the piling of an improbable imposture upon an improbably substitution upon an unlikley interpretation upon the rickety chair of knowing how someone will interpret an outcome thiat is required for some of these schemes to come off is…fanciful. Without them, certain books would flouonder, and certain schemes would appear transparent, but then the counter-argument would be that such schemes should be improved by other means. If all you can come up with is a bad idea, perhaps a) don’t write it down or b) wait for a better one.

Powers of disguise, too, are risky ground. It’s bad enough the number of times someone seeking to hide their identity in GAD simply puts on a big coat and hunches their shoulders — in most villages you’d be spotted in an instant and asked what was wrong with your back — from “I was in the circus” to “I was able to make myself up as, and adopt the mannerisms of, a completely different person” is a hop, skip, jump, forward roll, and day’s sojourn by bicycle away. Disguise is something with many facets, but the key point as which an author starts to overdo it is both staggeringly hard to define and blatantly obvious when encountered. I’ve written before about the use of costume to identify the malefactor in certain stories, but the gulf between clever utilisation of this theme and stepping wholesale into the life and existence of another person is, well, perhaps the difference between a good book and a terrible (or maybe an excellent…) one.

So how to prepare for the use of twins as Knox avers? Well, consider The Robthorne Mystery (1934) by John Rhode — no, you’ve probably not read it, but neither have I. There the use of twins is made the focus of the mystery: one of an identical pair dies, but which one? That’s a genius idea, allowing for the existence of the twins from the first page rather than hoping to hem and haw and spring it as a surpise near the last, and in twisting what is a hoary cliche redolent with disappointment and making it the focus of the book Rhode has shown a brilliant grasp of the principle. If the best defence is a good offence, in the thrust-and-parry of detective fiction a sure way to preclude having to defence yourself against a weak element of your surprise must surely be to put it front and centre, so that the reader no longer knows what surprise to look out for. If you can’t hide something in plain sight, why try to hide it at all? Write a book about the elephant in the room — this is what the successful examples above do, and the largely very memorable ends (man, I want to cite poor examples of twins to illustrate this, but would hate to ruin anything for you).

I should talk about Trent’s Last Case (1913) by E.C. Bentley, but as I continue to struggle to get more than a quarter of the way through that book, I’m perhaps not the best person for the job. What say you, people with more patience than I? Does it excel, or is it another case of something becoming too apparent through over-familiarity? Let the debate rage!

~

And there endeth the Knox Decalogue! Next Tuesday, er…something. Also, probably no review from me this Thursday because it’s been a helluva week and I’m exhausted and haven’t started reading anything yet. However, Saturday will (should) be the spoiler-heavy talk about A Murder is Announced (1950) by Agatha Christie, so make sure you’ve read up.

A bientot!