Imagine Hercule Poirot is talking to Sherlock Holmes about solving crimes. Poirot using order and method approach is convinced that the murderer is someone other than the victim’s relatives, their alibi’s all accounted for. Holmes is not so sure of that. He even quotes Sir Arthur Conan Doyle, his own creator.
“Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.”
Say the victim was poisoned overnight. The resident relatives are suspects. A box of chocolates was delivered that evening and the victim ate one or more though no poison was found there. Holmes argues that death from candy is impossible. Poirot, now knowing that death followed indulging in them is not convinced. Was it the wrappers, or in the box, or somewhere else?
As omniscient author (that’s you), the possibilities are numerous. There’s everything from the cook used a slow- acting poison in the victim’s dinner to the victim poisoning himself. Imagining plot is fun sometimes. Write it your way, just make it convincing to readers. Not to argue with Holmes, but sometimes working ideas include impossibilities in the solution.
In another case, a famous movie star is suspected in a love triangle murder, having been spotted entering the victim’s home. The murder occurred at two in the afternoon on October 11 this year. Investigations found a video of her bowing to and greeting the English Queen in Buckingham Palace October 11 for that exact time. It’s impossible for her to be in two places then. The recording hasn’t been altered and traveling the distance fast between scenes is impossible. Poirot and Holmes independently reach the same improbable solution. The famous woman has a twin previously unknown publicly. It’s only one explanation but that was used successfully in an NCIS episode in the past.
Astute readers may find holes in some scenarios, therefore authors need to think things through first and avoid incongruities. Research is key in obtaining relevant information.
Think of all the mysteries concerning trains for instance – Murder on the Orient Express (Agatha Christie), Strangers on A Train (Highsmith/Hitchcock), The Girl on the Train (Paula Hawkins). If you know nothing about trains, how frequently they stop, average speed, or destinations, research is needed. I’ve travelled on Japan’s Bullet Train and local commuter ones. They’re very different and also in types of passengers, which you’ll want to use in writing background for the story.
Imagining that Poirot and Holmes are riding on the train as you think of story possibilities could keep it interesting and importantly logical.