Fair Play

I've spent a lot of time thinking about detective fiction lately. I'm an unabashed fan of Golden Era detective stories: you know, the ones with the brilliant detective who goes to an English country house and discovers that the doctor killed the matron of the family even though everyone says it's either the butler or some mysterious outsider. Agatha Christie is widely regarded as the queen of the format, and remains one of the best-selling English-language authors ever. If you're going to strike up a literary conversation with a stranger, you're statistically better off bringing up Hercule Poirot than Harry Potter.

But there are Commandments to be obeyed when writing GE-style fiction! Knox's list, as posted in Wikipedia, is pretty useful. Reasonably applicable to sci-fi mysteries, too. I'll annotate with my thoughts.

1. 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. Agatha Christie famously broke this one in a book that a lot of people think was a total cheat. What Knox is getting at, I think, is that the reader shouldn't be coerced into identifying with the criminal. For a sci-fi story this has a different reading: it is traditional in these works to have a character stand in for the reader. Knox would say that this character should not be the killer.
   
2. All supernatural or preternatural agencies are ruled out as a matter of course. This holds true, of course, for science fiction, but I'd go further: any science related to the murder itself ought to be impeccable or the story will feel like a double cheat. I've never seen this broken in a way that was done well: this may very well be the one truly unbreakable rule on this list. A number of excellent stories have had the appearance of breaking this rule, right up until the last page, but these days you'll just invite unflattering comparisons to Scooby Doo.
   
3. Not more than one secret room or passage is allowable. My take on this is that the reader deserves to know the lay of the land as soon as possible. One twist on this, says Mr. Knox, is acceptable in the name of an interesting plot, but more than one wears thin. I'd go so far as to say that any such cartographical twist ought not be introduced after the first two-thirds of the story. As far as science fiction goes, I think this can be extended to the laws of physics and the rules of the milieu as well: all of a sudden faster-than-light travel turns out to actually be possible? OK, there's your one allowed "secret passage," good luck with it. But there's a caveat...
   
4. No hitherto undiscovered poisons may be used, nor any appliance which will need a long scientific explanation at the end. This one's a lot more important in sci-fi, I think. Part of fairness is understanding what's possible. But also, these things let the readers off the hook, lets them say, "Oh, I had a good excuse not to get that." Rubbish! This gets back to #3, in terms of knowing what's possible. One twist is fine, but it had better not be the key to the whole mystery!
   
5. No Chinaman must figure in the story. Like the man says, no Chinaman. Er, wait. How about, no inscrutable foreigner who the audience simply can't relate to, and automatically suspects? (Aliens might well apply, depending on milieu) Even then, this is kind of a lame rule. I'd rephrase it, "No Chi -- er, no inscrutable foreigner should be the killer" Otherwise the author is pretty much let off the hook for a believable motive, and the reader's only clue will be simple xenophobia. Then again, the presence of the Chinaman can't be an excuse not to cast doubt on some other character.
   
6. No accident must ever help the detective, nor must he ever have an unaccountable intuition which proves to be right. This one holds up pretty well, but is damned hard to pull off. This commandment is most often partly broken in the "Dimwitted assistant accidentally says something that puts the detective on the right track" trope. Watson did this, Captain Hastings did this, Magersfontein Lugg did this, countless one-appearance befuddled Scotland Yard detectives did this -- and then were obliged to feel good about having contributed! This trope can be done well, especially if it is a way of giving an extra clue to the reader, but often is not, and just seems like an unfair insult to the poor benighted Dr. Watson.
   
7. The detective himself must not commit the crime. This is related to the first commandment, as the detective is also often a focus for audience sympathy. This is not to say, however, that the detective must not commit a crime, just not the crime being solved. Otherwise you're just toying with your readers, making them play catch-up.
   
8. The detective is bound to declare any clues which he may discover. This is an important one, and so often broken. The clues don't have to be declared in a way that highlights them ([BLINK]CLUE HERE!!![/BLINK]), but the reader should have access to all the information the detective does, at about the same time (if not more and earlier!) Context is key during an investigation: you'll read an interrogation differently if you already know that the suspect's alibi has been blown. If the detective merely suspects something, however, that information can be safely kept. As far as science fiction goes, that means that relevant science and facts about the milieu have to be trotted out as early as possible. It's not fair for a detective to sit and interrogate someone who obviously doesn't know how anti-gravity works and not clue in the reader.
   
9. The stupid friend of the detective, the Watson, must not conceal from the reader any thoughts which pass through his mind: his intelligence must be slightly, but very slightly, below that of the average reader. If you're going to have such a character, he needs to be a comfort to the reader, as a companion and guide through the universe being inhabited. Any story with a Watson tends to result in a dozen put-downs: if Watson's ahead of the reader, those are going to sting. This is not to say that Watson should not have information in his own right! Just that any information he has (such as resulting from his medical training) should be provided quickly and clearly to the reader. Having a Watson who knows the milieu well can be a real benefit in a science fiction story, but I would say that there's a serious risk of being ham-handed here, overwhelming the reader with exposition. Tread lightly!
   
10. Twin brothers, and doubles generally, must not appear unless we have been duly prepared for them. Ditto clones, holograms, and someone time-traveling from the future back to his own timeframe.
    

If you read through that list thinking, "Argh! I can think of a dozen potential stories that break this rule to result in a good mystery!" then rant about it here, then go write that story! The rules aren't hard and fast, and I believe that Agatha Christie went out of her way to break every single one. Like many rules related to writing, the key is not to avoid breaking the rules, but to only do so explicitly and with understanding of why they are there.

I'm a bit too tired to go into Van Dine's 20 commandments in this much detail, not least because there's so much overlap. A few do stick out, though:

• There simply must be a corpse in a detective novel, and the deader the corpse the better. No lesser crime than murder will suffice. Three hundred pages is far too much bother for a crime other than murder. After all, the reader's trouble and expenditure of energy must be rewarded. This one makes me laugh, and yet it does give me pause. Grand larceny plots (jewels, natch) are a favored exception to this rule, and yet it's hard to imagine this translating well in a future society. The scarcity and value of physical belongings may seem odd, even tawdry, in many possible settings. If the victim's response to the loss of a diamond the size of a bowling ball ought to be, "Damn, I'll have to grow another one. At least my poor aching back will get a week's rest." then grand larceny may not work. Grand larceny has to be really ludicrously grand for this to work in many milieus. And of course, "Recover the secret files!" plots (except maybe blackmail) are in many ways already outdated: cats leap out of their bags and simultaneously pop out a million kittens these days. Also: be careful in choosing your metaphors. Moving on.
  
• A servant must not be chosen by the author as the culprit. This is begging a noble question. It is a too easy solution. The culprit must be a decidedly worth-while person — one that wouldn't ordinarily come under suspicion. No robot killers, unless you're Asimov. And, as I recall, not even then.
• Secret societies, camorras, mafias, et al., have no place in a detective story. A fascinating and truly beautiful murder is irremediably spoiled by any such wholesale culpability. To be sure, the murderer in a detective novel should be given a sporting chance; but it is going too far to grant him a secret society to fall back on. No high-class, self-respecting murderer would want such odds. Agatha Christie famously broke this one in The Big Four, and it was pretty much her worst book ever, by an enormous margin. This notion that the murderer ought to be individually culpable can be broadened in a science-fiction to include, for example, the Borg. The military and government tend to be far more sinister in the sci-fi tradition than in Golden Era detective fiction, or Van Dine would probably have included them as well.
• A detective novel should contain no long descriptive passages, no literary dallying with side-issues, no subtly worked-out character analyses, no "atmospheric" preoccupations. such matters have no vital place in a record of crime and deduction. They hold up the action and introduce issues irrelevant to the main purpose, which is to state a problem, analyze it, and bring it to a successful conclusion. To be sure, there must be a sufficient descriptiveness and character delineation to give the novel verisimilitude. This one is a challenge to the science fiction author, who must carefully weigh the needs of the milieu. If the setting is so cliched that the reader won't need much introduction, then you may lose that reader for whom the science is first and the mystery second. On the other hand, if the setting is so outlandish that explaining it takes forever, your story might only progress at a snail's pace.
  

Of course, in all of these rules, there is one unspoken: The story must make sense. The murder method may need to be novel and clever indeed to fool the forensics tools available to a 2Nth-Century detective! John W. Campbell thought it impossible, only to be proved wrong by Isaac Asimov. But that's another post.