#808: Reflections on Detection – The Knox Decalogue 8: Declaration of Clues

Twenty months ago I set out to examine each of the ten rules in Ronald Knox’s detective fiction decalogue in laborious detail; this month, that project will finally be completed. Then I can finally return to The Criminous Alphabet, eh?

Here are the links to everything:

Concerning the declaration of clues, arguably the defining precept of the Golden Age, Knox says:

The detective must not light on any clues are not instantly produced for the inspection of the reader. Any writer can make a mystery by telling us that at this point the great Picklock Holes suddenly bent down and picked up from the ground an object which he refused to let his friend see. He whispers ‘Ha!’ and his face grows grave — all that is illegitimate mystery-making. The skill of the detective author consists in being able to produce his clues and flourish them defiantly in our faces: ‘There!’ he says, ‘what do you make of that?’ and we make nothing.

If I had to pick a single aspect of detective fiction to explain what makes it so appealing to me — and you’ll be surprised to learn that I almost never do, as if the people I meet day-to-day aren’t interested or something — it would be that sudden reversal of realisation that comes from having been completely wrong in your interpretation of a clue. I have spoken before about what I consider to be perhaps the finest example of this that the Golden Age ever produced (no, I’ll not name the book again, since it runs the risk of spoiling it for the exceptionally watchful reader), but what’s so wonderful is that the era is littered with examples…indeed, so jam-packed that single books contain multiple examples. The holy grail of this is arguably the situation in which the misinterpretation of one clue results in the misinterpretation of another and so on and so forth until you find yourself miles away from the correct answer simply by an unassailable chain of logic built on one faulty piece of reasoning. Aaah, good times.

“Nice try, Jim — I know you haven’t spoken to anyone in months.”

Perhaps the closest we came to that in the Golden Age was The Poisoned Chocolates Case (1929) by Anthony Berkeley, in which an apparently simple poisoning is provided with no fewer than six distinct solutions (and Martin Edwards even found space for a seventh — and I think there’s ground for an eighth) based on subtle interpretations of various points. It’s interesting to note, then, that Berkeley, who is often seen as one of the most important figures in the development of Golden Age detective fiction — and I’m not going to disagree with that — wasn’t really all that bothered about this open declaration of clues that we’ve come to call ‘fair play’. Right from his debut The Layton Court Mystery (1925) it was clear that Berkeley was more interested in form ahead of function, preferring to play around with solutions and structure than worrying his head over precisely how such conclusions could be reached while also declared to the reader:

“Not much so far as actual hard-and-fast-evidence goes, I’m afraid,” [Roger Sheringham] concluded, “but we greater detectives are above evidence.”

I would suggest that the fair declaration of clues is the underpinning precept of the Golden Age, its inclusion as a matter of course being the point at which detective fiction stopped being the easy provision of answers that you had no investment in and instead became a game where you were genuinely given the opportunity to get to the answer ahead of the characters. The lunatic fringe that insists on Trent’s Last Case (1913) by E.C. Bentley aside, there’s a reason we talk about 1920 as the beginning of the Golden Age: because it saw the publication of The Cask (1920) by Freeman Wills Crofts and The Mysterious Affair at Styles (1920) by Agatha Christie, two novels whose authors went to great lengths to provide verbatim evidence for the reader to actually examine. The idea was hardly original, given that floorplans and specific dimensions of rooms had been a feature of stories long before this, as had evidence of interpretation that required no reproduction of footprints or handwritten letters, but when you compare the footprint diagram in Crofts’ debut with the sudden changing description of footprints in The Mystery of the Yellow Room (1907) by Gaston Leroux there’s a distinct change in intent. Leroux wants you to be amazed by the brilliance of his sleuth, Crofts wants you to be amazed at your own inability to see that which was right in front of you…and impressed by the perspicacity of the sleuth who did see it.

Were this concept not an exciting one, it’s fair to say that these two books, which brought not a huge amount else that was genuinely new to the crime story — please note, I’m not saying they’re not good books — would doubtless have been lost amidst the many others published that year and the school of crime fiction that resulted would have doubtless looked very different. Inspectors Burnley and Lafarge aren’t so very different from Dicken’s Mr. Bucket in Bleak House (1852) — they have the same tenacity, the same subtle way of making their will felt and ensuring they get the co-operation they need — and Hercule Poirot is an slightly humanised unknowable genius in the style of the various pretenders who sprung up in the wake of Sherlock Holmes, feeling to me somewhat closer to Dr. John Evelyn Thorndyke than Doyle’s creation (that’ll upset someone, I’m sure) if due to nothing more than his willingness to lean heavily into practical science and psychology. These were very much the same broad types we’d seen before, mutatis mutandis, and more of the same was not going to elicit the excitement that saw Crofts and Christie both open their accounts with such great sales.

“Mutati-what, now?”

A piece of Golden Age detective fiction is obviously defined by more than just its ability to declare its clues, as demonstrated by the sheer volume of stories produced under that banner which did no such thing, but this declaration when we see it — and, be honest, you’ve sort of come to expect it in books from this era, right? — became a feature enough of the time that it signified something meaningful as a development of how crime stories were being written and what they were setting out to achieve. When Anthony Horowitz drops a frankly brilliant piece of in-yer-face clewing in Magpie Murders (2016) or offers up a subtle variation on an oft-cited example from Hercule Poirot’s Christmas (1938) in The Sentence is Death (2018), those of us who enjoy our classic-era fiction get excited because we’re being invited into the game in a way that recalls Crofts’ reproduction of that footprint. It’s easy enough utilise the principle of the solution in, oh, say The Man in the Queue (1929) by Josephine Tey because…well, there’s not really much in the way of clued build-up to that. Doyle did this, G.K. Chesterton did it, Gerald Verner did it, Edgar Allan Poe’s Auguste Dupin flourished before us a sailor’s knot and a newspaper clipping mere moments before ushering in the solution to The Murders in the Rue Morgue (1841) — dammit, anyone can do that. The challenge is showing me what you’ve had all along — “defiantly in our faces”– which is more than sufficient to solve the crime, “and we make nothing”.

There’s an additional element to this, too, that I’d love to talk about in greater depth at some point: the Challenge to the Reader.

The modern, more realistic bent of a lot of crime fiction is somewhat inimical to the Challenge to the Reader, which introduces an element of artificiality by reminding the reader that they are, in fact, reading a piece of fiction, but I think it’s one of the most brilliant innovations the genre ever devised. In essence, the CttR is placed in a book at the point in the story by which all the information has been provided to the reader, and informs the reader of this and invites them to put the preceding information into a pattern that explains the mysteries in the text. As Rupert Penny said in the Challenge in his debut The Talkative Policeman (1936):

At this point the intelligent reader, if he has not already done so, should be able to attempt the solution of the problem with every prospect of success by taking thought, eked out where necessary with a guess or two. … Since nothing can too strongly express condemnation of those who use guesswork alone, making no attempt to exercise their reason upon the product of their imagination, nothing will here be said. The book was not written for them.


Such a Challenge is simply the game-playing of GAD raised to another tier — reminding you that the answer is within your grasp, and encouraging you to engage in what is, after all, the raison d’etre of this type of book; whay read something that’s going to give you the clues if you’re not then going to use them? I’ll be honest, I wish every detective novel contained a Challenge to the Reader, and I legitimately think it’s a shame that the conceit has dropped out of use. Not only does it reassure you that you’re now able to answer everything — no sudden newspaper articles or squinting butlers will drop in at the last moment to clarify things, you you can take time to think in the knowledge of being fully informed — but it’s also good for the author to ascertain that they’ve included the information the reader needs. Yes, much as not every GAD novel plays fair, not every Challenge to the Reader guarantees you’ve been given all the information you need (grrrr…) — and, in both cases, those that don’t form an unfortunate subset of the genre overall — but when they have and you can…man, that is pure reading nirvana.

Well, okay, not quite. There is a better possibility.

The very best, most purely enjoyable Challenges to the Reader don’t simply reassure you that you’ve been told everything, they also — as did Penny in Sealed Room Murder (1941), as did James Scott Byrnside in The Strange Case of the Barrington Hills Vampire (2020) — provide you with a list of specific questions for you to answer. This is delightful for two reasons: first, you can be fairly reassured that the author will have taken the effort to ensure than you can actually answer questions they are drawing your attention to, and second, the questions drawn to your attention are undoubtedly key to the core of the mystery and you often have no damn clue what the answers are. That Rumsfeld-esque sensation of knowing that you know what you need to know and yet feeling completely foxed by the very pointers being dangled tantalisingly in front of you is, for me, the exact sensation I hope my detective fiction elicits. If more authors in the Golden Age had been pushed to include specific questions to ensure the reader was well and truly tied up in sheer perplexity, requiring them to have hidden the clues cleverly enough for the attentive genre nerd to have overlooked even one of those answers…man, just imagine that book after book after book. I mean, sure there would be about half as much published in the genre, but given how much of it is forgotten, mediocre, or both, I don’t reckon we’d feel that GAD was any less hale and hearty as a result.

14 thoughts on “#808: Reflections on Detection – The Knox Decalogue 8: Declaration of Clues

    • Indeed Brad – hope you talk about every single one of the clues in A Murder is Announced in your upcoming podcast with JJ and Moira. You are reviewing one of my top 3 favorite Christies and I am looking forward to a thorough analysis of every bit of this wonderful book. I have re-read this one countless times and never tire seeing the way Christie gives the reader everything necessary to solve this and still manages to fool the unsuspecting reader.

      AMiA is a perfect example of the “clue declaration” in JJ’s excellent post.


  1. Another good example, not quite of a series of questions for the reader to answer, but of the author pointing out indirectly some vital clues, is in Carr’s “The Blind Barber” – this is why, although I can see the problems that others find with the humour, I rate it quite highly in the JDC canon – you really should kick yourself if you don’t spot the killer. (I should add that I didn’t!)


    • I believe that I’ve said before how much I enjoy the appearing body of The Blind Barber — like you, it never struck me much as a comedy, but the mystery element certainly isn’t the disaster its reputation would have you believe. And when you consider that it’s one of five books Carr wrote that year. it’s clearly an experimental piece…never repeated, but a salutary experience, no doubt.

      Carr does a similar thing, arguably more successfuly, in The Problem of the Green Capsule by having Marcus Chesney’s list of questions to which the various characters all have different answers despite all watching the same performance. That is, frankly, one of the most genius conceits the genre ever saw.


      • Yeah, the example of The Problem of the Green Capsule is probably unsurpassed. First you have a nice long list of explicit clues. Then you have the question of why they are clues. Then you have the puzzle of why everyone has different answers, and on top of that as the reader you don’t know which answers would be considered “correct”. The Nine Wrong Answers is another nice play on this.


  2. I’ve found there’s one defensible exception–the final (FINAL) bit of evidence that proves guilt beyond any doubt. It comes after the detective has determined the killer, meaning all necessary evidence has been shared with the reader. That final phone call or document or whatever is allowed to take place off the page. This information ensures the detective is correct but would be way too obvious if the reader was privy to it before the final reveal.

    Liked by 1 person

    • Oooo, you reckon? I dunno, this seems ripe for abuse. If the clue is repeating knowlegde gained elsewhere, fair enough, but if it’s a completely new piece of information…I’ve seen that done too much to have much patience for it.

      Of course, I will now be bombarded with a list of books I have favourably reviewed which did that exact thing, but I’d like to remind everyone of one key thing before that happens: my memory is terrible.


      • For clarity and brevity, here’s a stupid example. Let’s say the detective knows (somehow) the killer is allergic to tangerines. We get a dinner scene in which a character falls ill after dinner. Later, we find out Aunt Helen made her famous fruit salad. At this point, an attentive reader would say, “I bet that dude who got sick is the killer!” When the detective realizes it, he’s going to see Aunt Helen and find out she uses tangerines in her salad. The scene of the detective reading the recipe doesn’t have to take place on the page. It’s a major clue but not a necessary one.


  3. “…it would be that sudden reversal of realisation that comes from having been completely wrong in your interpretation of a clue.”

    I think there’s two variations of this: the clue that you knew was a clue, and the clue that despite being waved in your face, you had no … err… clue was a clue. I read your piece with the former in mind (“what is the meaning of the button in the victim’s hand?”, “what was the red dust on the victim’s sleeve?”), but want to call attention to the latter. It feels out of scope when you take Knox’s statement at face value, but I like to think it still implies in spirit.

    The author can slip a clue in front of your nose, but they should give you ample appreciation of that clue. What Carr did in The Corpse in the Waxworks is definitely way too subtle, even though it was done in plain sight (and I absolutely love it). I’m more thinking of the tricks that you see from Brand, where a clue is flat out flaunted repeatedly without the reader ever seeing it as a clue. A more stretched application of this is the scene that is interpreted in the wrong way (Carr and Christie having excellent examples); not quite a clue, but the point holds that the reader and the detective have access to the same information.


    • Yeah, this is a good distinction to draw — the red powder on the floor in The Seat of the Scornful vs. some event you’ve seen, attributed some relevance to, and forgotten. There’s something especially lovely about being caught out by the latter, but personally I’m such a fan of being told something is relevant and not knowing how or why — that reveral of expectation is all the moe enjoyable for having had time to marinate.


  4. The last-minute damning evidence is a resource I quite like as long as it’s feasible to infer the missing x. I would say it’s actually one of the things I like the most.
    Let’s say a suspect always has a hand in his pocket and never uses it, even when he should have. A clever reader might suspect a prosthetic, thus, if the detective mentions this new item towards the end of the book, the sly reader will nod, and the unaware will experience a sudden realization.
    So, closing the case with the help of something “new” is not necessarily a bad thing.


  5. If I had to pick a single aspect of detective fiction to explain what makes it so appealing to me — and you’ll be surprised to learn that I almost never do, as if the people I meet day-to-day aren’t interested or something — it would be that sudden reversal of realisation that comes from having been completely wrong in your interpretation of a clue.

    You mean to tell me that people don’t find it interesting when you sidetrack random discussions onto the topic of mystery fiction? I never would have guessed! This explains so much! XD

    That’s my favorite aspect of mystery fiction as well, along with the point where you see all of the clues you missed that were in plain sight all along. One could say that they’re two sides of the same coin, as at root they’re fairly similar forms of misdirection, both tricking the reader into making an unwarranted assumption (Although I suppose that could be said of any form of misdirection). The only difference is that one leads you into a wrong interpretation of a clue, while the other tricks you into thinking that a clue isn’t a clue at all. (One book that I think does both of these things well is The Skeleton in the Clock. The way that the clues are hidden in that book, such that you don’t notice them even while you’re lead into paying attention to the very spots where they’re hidden, is absolutely brilliant.)

    I agree with you about challenges to the reader as well. They’re wonderful and would that they were used more frequently. Of the ones I’ve read, I’d say that my favorite, albeit a somewhat unconventional example, is The Nine Wrong Answers. I love how it actually points out exactly where in the book the misdirection lies, and yet the solution still comes as a surprise. Talk about flourishing clues!


    • They don’t! It is the oddest thing…

      I’m interested in The Nine Wrong Answers for precisely the reason you’ve outlined above — I was aware that this is an element of its construction, and I think it’s especially wonderful to say “Aha, well you’re thinling this but you’re wrong…”.

      A sort of variation on this is when a novel uses the kind of HIBK approach and says something like “It was only much, much later that she would come to appreciate the importance of those kippers” — and you wrack your brains trying to think of any reason for the kippers to be important. It’s an occasionally over-used approach, sometimes to poormeffect, but like most fo the tropes the principle is great when deployed intelligently.


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