Thou shalt not break Knox’s Third Commandment

Way back when God was a boy, in 1929 to be precise, Ronald Knox, a Catholic priest and author of such Golden Age detective fiction novels as The Viaduct Murder, composed a set of ten commandments for his fellow members of the Detection Club, for the writing of their detective novels. He was not the only one given to setting out such rules. SS Van Dine came up with twenty different rules in a 1928 article. And Raymond Chandler also came up with another decalogue which, in a sideways blast at what he perceived as the effete and unrealistic English detective stories, focused more on what makes a good novel rather than a good puzzle plot – reflecting his view that too often the puzzle got in the way of good writing.

Naturally, Knox’s fellow club members set about breaking every one of his rules with cheerful energy. Indeed, they had all been breaking them equally often before they were codified. But, and this is crucial, they and the other Golden Age writers knowingly broke Knox’s commandments with malice aforethought. They transgressed for effect and for their own ends. They did not merely blunder into their breaches to no purpose.

My doubts about the writers of modern crime fiction is that they are unwitting breakers of the rules. Many modern crime writers express reverence for the Golden Age authors and cite them as major influences since their childhoods. Others at least acknowledge that the Golden Age authors, whatever their short-comings from a modern perspective, did at least manage to sell vast numbers of books and so cannot be dismissed out of hand.

It is therefore somewhat depressing for me to find that so much of the modern crime fiction I read is stuck in stereotypical tropes. The cliche which concerns me here is the penchant for the serial killer in too many of the newer psychological crime thrillers of the “Noir” end of the spectrum to break Knox’s Third Commandment:

“Not more than one secret room or passage is allowable.”

Now, it seems, every Tom, Dick and Harry on a killing spree has recourse to a hidden basement. I am sure that the dreadful crimes of Josef Fritzl, who incarcerated his daughter in a secret underground annex and sexually abused her for 24 years, and which came to light only in 2008, have been an influence on this recent trend. Now, as back in the Golden Age, real life crime inspired the writers of fictional crimes.

Knox, when he devised the rule, was concerned with ensuring the Golden Age plots did not descend into absurdity. He knew that the plot devices employed by his fellow writers frequently stretched realism – as Chandler accused them of doing – but he wished to keep authors on the correct side of breaking point. The reader will suspend their disbelief but only so far. At some point their credulity is overtaxed and the whole edifice collapses beyond any shoring up on the part of the author – or his perpetrator.

I would like to consider the practical implications for the lone serial killer in constructing his underground chamber of horrors for inclusion in what might, with some justice, be regarded as this sub-genre of modern crime fiction.

Beneath his apparently normal suburban house, he must excavate a chamber that measures some two metres in all directions as a minimum. This gives room for him or her to stand upright and for the victim to do so too if they are not physically restrained. It also gives room for the imprisoned victim to lie down, or to be tied down if that is the perpetrator’s preference, full-length on the floor – if no bed is provided. It also gives space for the killer to come in and torture the victim if that is his particular thing.

Imagine that space. It is the size of a small box-bedroom in a modern home.

What this requires is that 8 cubic metres (2m x 2m x 2m) of soil has to be removed. Dug out by the lone killer without the benefit of power tools. It must be done by hand to avoid the noise and vibration – let alone the difficulties of smuggling any sort of serious earth moving equipment into and out of the supposed cozy family dwelling.

Each cubic metre of soil weighs somewhere between 1,200 kg and 1,600 kg – depending on how compact it is. So 8 cubic metres represents between about 10,000 kg and 12,500 kg of soil.

Shifting that, once the killer has dug it out, is no small matter. A large family estate car, say a BMW 5 series, has a maximum load-carrying capacity of about 600 kg – including the driver (taking up the better part of 100 kg himself). So we are looking at approximately 20 to 25 full car-loads of earth to take to the local tip.

And all of it has to be hauled out through the house, from wherever the secret panel is that conceals the entrance to the bunker, and loaded into the car. Managing this without leaving any trace, particularly of the sort that a police investigation team – or even more painstaking, a forensics team – might notice would be a spectacular feat of cleaning up after oneself. Think how quickly carpets or even wooden floors show up the dirt you tread into the house if you are not meticulous in taking off your outdoor shoes when arriving home. Think how hard it is to get them looking clean again if you neglect them in this way for even a relatively short period of time. And how they never do quite look as good as new. Now multiply that effect by the impact of shifting the equivalent of a decent sized garden’s-worth of top soil through the house. That’s an industrial scale challenge for even the toughest of steam-cleaners.

But let’s return to all that digging our serial killer is doing in his patient plan to construct the perfect secret torture chamber for his victims. How long is this going to take a man on his own?

To answer that question, based on practical experience of underground digging in secret, I must return to Tom, Dick and Harry. These were the nicknames given to the three tunnels dug by Allied prisoners of war at the Stalag Luft III camp where they were held by the German Luftwaffe. In his book The Great Escape, Paul Brickhill explains that the tunnels were constructed over a period of 12 months from March 1943 to March 1944  (with a three month break when one of the tunnels was discovered by the guards). The work was carried out by some 600 of the prisoners. Harry, the longest tunnel and the one through which the eventual escape was made, measured some 102 metres in length and was slightly more than 50 cm high and 50 cm wide. The volume of soil removed was, therefore, of the order of 25 cubic metres.

The other two tunnels were shorter but would require broadly similar volumes of soil to be dealt with.

The dispersal of the soil – much done through pouches concealed in the trousers of the airmen by which the soil could be released and then hastily trodden into the surrounding earth to disguise it (since it was a different colour from the topsoil) – took an estimated 25,000 trips. Clearly here, by the way, we have a vital clue for the maverick detective in the hunt for his serial killer: forget the shifty, nervous-looking creep in the skinny jeans, it’s the bloke with the baggy trousers you should be watching.

So if we allow that the 600 POWs, working in shifts, took a nine months to dig three tunnels whose total volume was perhaps approaching 75 cubic metres – that is about ten times the volume our hypothetical serial killer must deal with on his own – we have some measure of the scale of the task when tackled in the real world. He is facing some 45 man-year’s worth of work at the rate they achieved to build their secret tunnels.

Of course, the 600 POWs were not working full time on the escape tunnels – they had to maintain a presence in the camp under the watchful eye of the guards who would notice the absence of any significant number at any given time.

But, our serial killer must also conduct his secret life as some sort of human mole behind a facade of normality. He may be holding down a full-time job. His murderous hobby cannot be carried out to the exclusion of everything else if he is to appear like the average man in the street to his neighbours and work-colleagues – even if with hindsight they may reflect that he was “a bit of a loner”.

Nevertheless, 45 man-year’s worth of work does seem a lot to tackle as mere preparatory task before one can begin to indulge even the sickest of fantasies.

So I am forced to conclude that Reginald Knox was right to bar the use of secret rooms and passages when he drew up his list of commandments.  He was right not only on purely aesthetic grounds, that they were an affront to the intelligence of the reader and spoiled the enjoyment of a well-plotted story if over-used, but also on purely practical grounds. Creating the secret chamber would be quite simply beyond credible bounds as a one-man feat of engineering. As a result, whenever I now read a novel in which the serial killer conducts his business in a secret underground bunker I feel entitled to throw the book across the room in disgust – where it hits the opposite wall almost exactly 2 metres away…



3 responses to “Thou shalt not break Knox’s Third Commandment

  1. Pingback: Ronald Knox: The Shorts Stories (1931-1947) – The Reader Is Warned

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