The Rules of Mystery
Ever since the explosion of the mystery genre during the Golden Age of Detective Fiction, there has been no dearth of whodunnit stories. In 1929, Ronald A. Knox compiled a list of ten rules he claimed all good mysteries followed. Collectively known as Knox’s Decalogue or Knox’s Commandments, they embodied the spirit of the 1920s ‘games’, as they were called. A more comprehensive list of 20 rules was published by S.S. Van Dine, but they never reached the same popularity that Knox achieved. While not being up-to-date with modern standards, the edicts still provide some insight into the correct way to write a mystery.
The first Commandment goes: ‘the criminal must be mentioned in the early part of the story, but must not be anyone whose thoughts the reader has been allowed to know.’ The half is still followed religiously – nobody in their right mind would spring the murderer role onto a character not known early on by the reader – but the second part is no longer valid. Taking the example of Into the Water by Paula Hawkins, the culprit’s viewpoint is shown often enough even before the reveal. This is actually reasonably easily achieved: the Unreliable Narrator trope comes in handy here, though it takes a bit of work to perfect the character’s voice.
‘All supernatural or preternatural agencies are immediately ruled out’ is the second. This generally still holds true, but more loosely. Since many more detective stories are being set in universes where magic exists, the second rule effectively changes to ‘Any forces unfamiliar to the detective are to be ruled out.’ Of course, the reader needs to be informed of the working of magic near the beginning, but that is a relatively minor obstacle in the act of storytelling.
The third is: ‘not more than one secret room or passage is allowable.’ This one should be taken as a rule of thumb rather than a rigid commandment. Keeping track of the house’s layout is tiring for a reader, especially since they have to construct the whole thing in their minds from the description. Adding more than two secret passages shows incompetence on the author’s side because the plot requires so many hidden details to stand on its own. If it seems that you absolutely need more, try and sketch out the crime scene and see if you could do away with one, or make it a normal passageway instead. Instead of secret rooms, use mop closets and other generally overlooked storage spaces.
The fourth is one which I believe still applies to this day: ‘no hitherto undiscovered poisons may be used, nor any appliance which will need a long scientific explanation at the end.’ If it requires more than a paragraph’s worth of exposition at the end, do away with it, or find a way to provide the information within the story itself. One of the reasons mystery is such a popular genre is because there is an opportunity for the reader to solve the crime on their own; however, if you include devices that need in-depth knowledge of a particular field as a significant plot point, there is no doubt the viewer will feel cheated.
The fifth has firmly passed into the realm of obsolescence: ‘no Chinaman must figure in the story.’ The wording itself is racist, nevermind the rule: using the word ‘Chinaman’ (making it seem like being Chinese is the only important thing about the character) instead of ‘Chinese person’. The 1920s weren’t amazing times to be alive for anyone other than the cishet white upper-class male; almost every form of bigotry – be it sexism, racism, homophobia, transphobia or classism – was rampant and indeed socially required.
The sixth is true for any story, not just mysteries: ‘no accident must ever help the detective, nor must he ever have an unaccountable intuition which proves to be right.’ While having an incredible intuition is fine, it is always better to have a proper explanation of the character’s thought process. Likewise, small fortunate coincidences are acceptable, but no major plot point should ever be solved through luck alone, unless you are writing a comedy.
‘The detective himself must not commit the crime’ is the seventh Commandment. It is no longer considered to be as sacred as it once was, but is still generally followed, probably because there are only so many original plots that can be written with the detective as the killer. (Spoiler Alert) Agatha Christie’s The Mousetrap is an excellent counterexample to this edict.
The eighth states that ‘the detective is bound to declare any clues which he may discover’, which is perhaps another one that still retains its worth, if for no other reason than to ensure the audience is on the same page as the detective regarding the plot. However, since most mysteries of this day do not have the investigator as the main character, this rule tends to not be encountered particularly often.
The second last directive says that ‘the detective’s sidekick must not conceal from the reader any thoughts that pass through his mind: his intelligence must be slightly, but very slightly, below that of the average reader.’ While some still religiously follow this, most have moved to a different setting where there may not necessarily be a sidekick. Even if there was a sidekick, their viewpoint might not ever be shown.
The final rule is another one which has mostly stayed strong: ‘Twin brothers, and doubles generally, must not appear unless we have been duly prepared for them.’ Twins are impossible for a reader to naturally predict (blame Occam’s Razor) and are thus frowned upon, unless there has been some clear indication of their existence. One example I can give is from the manga Dead Tube (a rather gory and violent story, which is nevertheless a fantastic thriller). At one point, the main characters are forced to stay on an island with a serial killer and several other ‘players’ like them as part of a ‘killing game’, with the goal being to catch the murderer. On the very first day, they find the severed head of the de facto leader, after which all hell breaks loose. As more and more people turn up dead, all the leads turn to dead ends, until finally only the main character’s group is left. The protagonist, however, is a filmmaker by passion, with an eye for detail. He quickly worked the mystery out: the severed head had a mole on the cheek which the original player didn’t, who turned out to be the murderer. The head they had found belonged to his nearly-identical twin, who was killed a day before the main cast arrived on the island.
The reason barely any of the list still applies is because of the shift in the method of storytelling. Golden-age games had a rigid formula: a detective (usually with a sidekick from whose view the story is told) learns of a mystery defying common sense. They both investigate the mystery, finding various clues. The detective then brilliantly works out the entire sequence of events in a single bit of exposition, and the story wraps up. In today’s mysteries, the story is told from any number of perspectives, and the detective isn’t nearly given as much importance. The process of the solving the conundrum is not the sole goal; character development has equal importance: humans – and sometimes the world they inhabit – are the main element, not the crime.
While Knox’s efforts may not be of much use today, they aren’t worthless: they capture the prevailing sentiments of a bygone era, conveying to us the customs and cultures of past times. At the very least, the next time you read any 20’s detective fiction, you would see how these rules were each being followed, and that despite the constraints, each story was unique and enjoyable in its own right.
Proofreaders: Durga C., Mokshit N., Smit W.
