#598: Reflections on Detection – The Knox Decalogue 3: Secret Passages

Decalogue header

For the final time this year, then, let’s take another dive into one of Monsignor Knox’s detective fiction decalogue rules.

Here’s how things stand:

Rule 1: The Criminal
Rule 2: The Supernatural
Rule 3: Secret Passages
Rule 4: Undiscovered Poisons
Rule 5: No Chinamen
Rule 6: No Accidents
Rule 7: The Detective-as-Criminal
Rule 8: Declaration of Clues
Rule 9: The Stupid Friend
Rule 10: Twins

And here’s Rule 3:

Not more than one secret room or passage is allowable. I would add that a secret passage should not be brought in at all unless the action takes place in the kind of house where such devices might be expected. When I introduced one into a book myself, I was careful to point out beforehand that the house had belonged to Catholics in penal times. Mr. Milne’s secret passage in the Red House Mystery is hardly fair; if a modern house were so equipped – and it would be villainously expensive – all the countryside would be quite certain to know about it.

Of everything Knox sought to confront in his decalogue, this is the one rule which I imagine requires the least defence or explanation.  Secret rooms and passages can have their place, but too much of anything becomes wearisome when it is used — as it has been countless times, in too many novels, short stories, and movies to name here — to repeatedly explain away or allow criminous deeds.   If four people disappear from the Mysterious Cursed Room in your family mansion, chances are it’s a secret passage that’s enabling such a thing.  If people disappear from two different rooms, each with a secret passage of their own…well, come now.  And as the number of rooms from which our Victorian Villain may snatch the unwary multiplies, so diminishes our interest in these answers when they’re reached.

So, what to say about Rule 3?

Firstly, I suppose, that — while the secret passage suffered something of a tailing-off in popularity as crime fiction lowered itself from Gothic castles populated by looming, glowering Obvious Bad Types and took up residence in the vicarage, the boarding house, the train carriage — the secret room never really went away.  It may have reduced its stature to a mere nook (hidden beneath the floorboards, say) in which stolen goods may be stowed or a killer may escape detection, but as such it allows a certain degree of ‘Purloined Letter’-style oversight to excuse its efficacy. and retain its “secret” nature Nevertheless, the most effective deployment of this principle — ‘Hot Money’ (1939) by Carter Dickson, say, or (at a push) ‘The Scientist and the Vanished Weapon’ (1966) by Arthur Porges — works wonders when ingenuity is brought to it rather than seeing the “secret room” as a literal room.

And so, in its own way, Rule 3 casts a light not so much on the literal interpretation of these ideas, but on the myriad ways that GAD would take the essential principle of something and adapt it over and over with a fecundity that still renders these ideas so compelling all these years later.  When even Norman Berrow — who loved a secret room or passage as most of us love the sun on our skin — takes the secret room trope and plays with it enough to hide a room inside a room, you know your concept is going through some revelations.  And so as the idea of a hidden room became a hidden compartment (not really all that revolutionary, doubtless many a scandalous letter was secreted in many a Gothic desk over the years…) the revolutionary principle picked up by GAD was surely not to redefine what “room” meant as, more tellingly, to redefine the nature of secrecy.


“G-good heavens!”

Declaration is covered in Rule 8, and so still ahead of us in this meander through Knox, but arguably the defining principles of GAD reached their pinnacle when the author boldly shows you what you need to know and yet you fail to appreciate it: the butler squinting at a calendar, an unopened letter on a desk, a key disarranged from the pocket of the victim: in their respective books, they tell you a lot more than it might initially seem.  The talent of GAD was in getting the reader to see the significant as mundane and vice versa, and so the idea of a secret passage or room becomes in many ways a challenge to the reader to interpret what they’re told, and to recognise the significance of that event when it happens (we can’t, after all, go about tapping on the walls or measuring corridors — and any floorplan that goes to the effort of providing exact measurements of space is, well, tipping its hand somewhat). Something is secret if it is hidden and GAD, after all, revelled in flaunting the recondite under the noses of those who watched.

To pick examples from outside the Golden Age so as not to spoil too much: there’s an argument that Dr. Grimesby Roylott (second-best name in the canon) utilises a secret passage in the Sherlock Holmes story ‘The Adventure of the Speckled Band’ (1892), since we know there’s a passage of sorts, and yet do not intuit its meaning.  Equally, out the other end of the era,  Murder in the Crooked House (1982, tr. 2019) by Soji Shimada makes it plain for all to see that a ‘secret’ passage is very much at the heart of that novel’s seemingly-impossible stabbing…and yet, in brazenly declaring the means by which such access is made, the misdirection — or perhaps overstatement in this case — would be sufficient to hide its presence from the majority of readers.  I’m being more careful around GAD examples here because the risk of exposing too much in terms to well-judged public secrecy, but you could doubtless cite a great many cases in the appropriate time period where the same was applied.

And so what we also have here is the exposure of the lie commonly put about, as evinced in the introduction to this series, that the Knox Decalogue was something taken especially seriously by authors at the time.  Knox proposes a moratorium on concealed passages and rooms, and GAD responds with just about every form of secret, concealed, hidden, fully-on-display room, cranny, space, opening, corridor, alley, and crawlspace the human mind could devise.  And people say that Carolyn Wells and Wadsworth Camp made no contribution to the pinnacle of GAD…



The only other thing to discuss, then, is poor A.A. Milne getting yet another kicking.  I’m not entirely sure what to make of Knox’s assertion that the passage in The Red house Mystery (1922) is “hardly fair”.  It’s been a number of years since I read it, but don’t they spend, like, a full chapter discussing the various implications of the passage and its location?  Such as, it can’t originate from any but the ground floor or cellar, and that it would be unlikely to be on the “wrong” side of the house since the digging it would require navigating back past the foundations, etc?  And — though, again, it’s been a number of years — isn’t the fact of the  exit outside the house being in a particular place used to explain how one witness sees someone who must have come out of the tunnel but another doesn’t, since they would have passed them while in the tunnel (or similar — I’m not sure that book is so well-read as to risk spoilers)?  That’s no simply dropped in out of nowhere as used in the chain of reasoning to support a conclusion…so in what way is it “hardly fair”?  Dammit, man, define your terms!

Hmm, that appears to be it for this week.  Not gonna drag this out needlessly, but rest assured that plenty of tedious 3,000-word essays remain in the wings for when I pick this up again sometime in 2020.  The reader is fore-warned…

10 thoughts on “#598: Reflections on Detection – The Knox Decalogue 3: Secret Passages

  1. The “kicking” of The Red House Mystery is no doubt due to its huge popularity (for many years after its publication) among the public. I’m not saying it was jealousy, but it was jealousy. And surely this popularity was not because of innovation or brilliance, but rather because TRHM is a celebration of the detective story with a lot of warmth and good humor. As such it has every right to employ the secret passage–Of course it would have a secret passage!


    • It’s a flawed book, no doubt, and I can understand Raymond Chandler paying into it in ‘The Simple Art of Murder’ because Chandler had no perspective on the type of story the detective novel was telling and TRHM is an easy target (given that it has, like, three characters and two of them are the sleuths…geeeeeee, who could the killer be?). Knox seems to come out of nowhere here, slap it while it’s not looking, and then run for cover with no further word of explanation.

      Maybe I should reread it, in light of the classic GAD I’ve consumed since first encountering it (unsurprisingly, it ends up on a lot of “Hey, try this!” lists). A project for 2020, maybe…


  2. Agree with all you write here, but just want to apply Knox’s rule to my reductionist list of genre expectations, again:

    1. The puzzle shall indicate the solution.

    2. The solution shall account for the puzzle.

    3. The solution shall surprise.

    The prohibition (or limitation) on secret passages would seem to reflect (depending upon how one looks at it and how the issue is presented) either #1 or #3. If a secret passage is presented at the denouement as an explanation without earlier indication (clueing) it would certainly qualify as as the type of post-equals-sign element that is tacitly agreed upon as unacceptable and referenced by expectation #1. And even if indicated, it might be considered a violation of #3 as a solution that has lost its power to surprise via over-familiarity.


    • Undoubtedly, Scott. Should a secret passage simply crop up at the end — which, for a second, I thought might have happened in TRHM, since I recall vaguely mention of it in the summary chapter — to explain how suspect A could be both in the vicarage and at the scene of the murder, heads would roll (or eyes, at the very least).

      The concept of being surprised does then make it all the more interesting when we encounter a book from this (or any) era which legitimately surprises us — there’s a tendency to pre-empt what you know are going to be hoary rehashes of very, very old solutions (have just given up on a modern locked room novel which uses two of the oldest and then has the temerity to label itself brilliant). The secret passage is difficult to surprise with, then, because there’s either a passage for there isn’t. Hinting at one can only really be done through repeated use of it, since the possible ways to indicate its presence are rather limited.

      So, yes, I agree with your summary above. Man, I need to get less verbose.


  3. My stance on hidden rooms, secret passageways and invisible doors is very simple: only allowed in pre-1920s mysteries and acceptable post-1920s if the writer has a clever or innovative take on it. So pretty much what you said.

    Someone on the old JDC forum compared the harsh criticism leveled against The Red House Mystery to taking a sledgehammer to a butterfly or stomping on a flowerbed.


    • There’s a Carr novel (of which I am a big fan and others seem to like much less) which drops a secret passage a bit out of nowhere, and I just hooted with joy when it happened. And one of the best discoveries in my Adventures in Self Publishing throws a passage at us for sheer kick and giggles which is also a great deal of fun — so, yeah, there’s a time and a place, and it’s probably the one conceit of classic GAD which can be subtly misused without appropriate care and so go on to ruin everything. Who’d be a writer, eh?

      I am definitely going to reread TRHM at some point next year. Probably. It’s been a long time, and I feel it’s worth a revisit.


      • I know the Carr novel that you’re referring to, and it jumped to my mind immediately as an example of brilliant use of hidden passageway. The hidden passageway isn’t even really clued (in a roundabout way I suppose it kind of is), and I recall my initial horror that Carr had “violated a rule.” It’s so clever though in the way that it flips around expectations of what a secret passage should be used for. In fact, I’ll suggest that Carr could have flat out stated there was a hidden passage right up front, and I still never would have come close to the solution.


        • Yeah, you’re right — there’s that initial reaction of “Hey, hang on, that’s not really on, because now it explains everything” and then you think about it for a minute or two and go “Yeah, no, it doesn’t explain anything, actually” 😂

          There was an earlier book which dropped in a secret passage, too, but it seems Carr grew out of them fairly quickly. Maybe after reading those Carolyn Wells novels Curtis posted about earlier he felt they’d been somewhat done to death…


  4. ‘I would add that a secret passage should not be brought in at all unless the action takes place in the kind of house where such devices might be expected. When I introduced one into a book myself, I was careful to point out beforehand that the house had belonged to Catholics in penal times. Mr. Milne’s secret passage in the Red House Mystery is hardly fair; if a modern house were so equipped – and it would be villainously expensive – all the countryside would be quite certain to know about it. ‘
    In context you see his reasons for saying ‘hardly fair’ (it not being supported by any historical background). The final sentence reads less like harsh criticism than a whimsical wink at what novelists can get away with.


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