Set theory, assumptions and the whodunit
As we know (and love), the whole idea behind a "whodunit" is to find out who does the crime. I have read quite a bit of the classic detective fiction stuff and prefer the old-fashioned and sanitised crime world of Doyle, Poe, Christie et al. The thought came to my mind that in some sense, in many of these, the reader is nominally invited to take a guess at who the culprit was (and if the butler really did it). The success of these plots (films/plays/TV serials all included) depends on presenting us with a choice of people.Take a typical Christie. A whole array of characters will be presented to us and the sleuth will eventually figure out who was the criminal in question. We can guess that as with any evolving genre of plot, initially the criminal was the most villainous of the lot (this is especially true of films - the audience will, with their experience of the movies, identify very early who the villain of the piece was, and it remained for the narrative to provide the links). There was a straightforward translation of the good-vs-evil template.
Holmes stories were not like Christie formats, in the sense that we did not see all the pieces at the same time the detective did. We would eventually marvel at Holmes unravelling a very mystifying set of items, but we travelled with Watson and Holmes hardly told him anything :-). We were usually meant to drop our jaws in awe. The Christie version was more of a jigsaw puzzle, where usually one was given several important pieces of information at the same time as the problem-solver was. The unlikeliness of the person was very central to her success and this didn't require her popular and geriatric detectives to bound about unlike Holmes, whose legwork was a vital part of his triumphs (which many a time excluded Watson and hence us).
So essentially, in the classic whodunit of the Agatha Christie variety, it came down to a set of choices. Method was secondary to this. As you read her books, your mind opened up to the possibilities - she cleverly manipulated our naivété & biases. Soon, she churned out an array of unlikeliest criminals and tried almost everything possible with rearranging the set. One can only guess, but it is not hard to imagine the Dame beginning with a group of characters and wondering "what if XYZ did it? How would one weave a story with that ending". At any rate, that is what I would do :-)
I'll avoid spoilers and instead recommend the following Christies as great examples of what I've just talked about. The Murder of Roger Ackroyd is of course her most famous work, and something that justifiably caused a lot of ripples in those days. Hercule Poirot's Christmas, Murder on the Orient Express, Ten Little Niggers, Evil Under The Sun and Crooked House are other examples where our inherent assumptions are cleverly challenged. As a finale, Curtain: Poirot's Last Case is also recommended.
From making several variations on individuals in a set, authors then moved on to even making it a subset of people - this, again, would have been very novel then. We have seen several examples on screen and page since, so it may not seem so new to us. So to maintain the twist that gives the whodunit its lastpage turning spice, some enterprising authors even increased the subset size to be almost as same as the complete set!
A day came when all this became very predictable, so creators again shook off the burden of making everything available to the viewer/reader. Now, sudden twists came in by the addition of characters midway through the plot or ingeniously reviving forgotten characters. An examples of movie in these cases would be certain David Fincher films. Certain Ed Norton films also had this element - and again, they challenge some assumptions we're led to making. This makes it a lot of fun. Occasionally, you lose the ability to predict the twist by gaining such a lot of "experience" - it happened with Identity and sadly, with the The Usual Suspects. Perhaps I heard about the latter elsewhere without actually making an explicit association. But the kick of the first realisation - that was lost.
TV serials like Columbo eschewed the whodunit path for a different "howdunit" approach (there was a Hindi remake of this concept featuring Anita Kanwar). But still, the whodunit holds sway. Jonathan Creek (will be writing about this extensively some day :-) ) was hence a rarity - it had both the whodunit and the howdunit given equal prominence. In several (would this be an example of "post-modern" consciousness?) cases, we now have reality and fiction overlapping - take a Hey Ram for example.
So what are the tiny variations left for writers of creative fiction to exploit? This is an interesting exercise for people like me who like the "puzzle" nature of whodunits rather than the more realistic American styles involving Marlowe, Spade etc. Perry Mason, the ubiquituous paperback, was a more classic British style than of the noir variety. Poirot stories didn't have any unnecessary subterranean complications and they lived in a less grey world, but I liked that a lot more. Jonathan Creek was, for me, very much in that mould with its tongue-in-cheek humour and a slightly unrealistic world, where the crime will be solved by our detective. There is a certain reassurance in all that :-)
{For some hilarious thoughts on the whodunit genre, read some of the Jeeves-and-Wooster stories by PGW, where Bertie usually has a whodunit at hand, but events prevent him from immersing himself in them. He also consults them with fervent interest with the usual imbroglios resulting. As a result of watching these British serials over the last one year and having read several British detective books over the last 20 years, I really envy the range of plots they have explored.}
I'm going to end this piece with one version of a "twist" that I had employed (so I'm cleverly using this opportunity to re-plug an old attempt of mine: A Head For Red). And perhaps the last movie whose ending totally surprised me and shook some assumptions was The Others.