"Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth." —Conan Doyle. A quote that seems to be the crux behind solving anything with a hint of mystery.
Mysteries can be compared to puzzles. However, the supposed 'pieces' of this puzzle a sentient and emotional people who are not willing to just stand around unless confined by a specific reason to do so.
Even in detective games, the criminal is always trying to hide the evidence, which in turn leads to the slipping up and accidentally revealing their true identity. The whole 'detective vs criminal' shtick is popular in the wake of Sherlock Holmes, despite it not being the only way to write a mystery narrative.
The essential part to be aware of when writing a mystery isn't what information you share with the reader but the 'legitimacy' of that information. If it came from a suspect, then it is natural to assume the information to be false. Contrarily, if it was to come from someone the 'detective' trying to solve the mystery trusts, then the reader would take is as fact.
However, just because I say that doesn't mean that trusted people should always be believed and suspects should be ignored. After all, the beginning of any mystery always makes sure that no one is safe from being seen as 'suspicious', even friends.
In this context, you could say that until proven otherwise, there is no possible way for anyone to be trusted. I find this kind of setup to be a little too simple to work with since there are no stakes for the main character or even drama caused by suspicion.
On a related topic, one of my favourite Light Novel Author by the name of Nishio Isin is a master at creating intrigue through subtlety. In his most widely known works of the Monogatori Series, even the main character can be considered the 'culprit' sometimes in the mysteries he's trying to unravel.
The enjoyment I get from reading his works has nothing to do with the mysteries themselves, but rather the way they are presented. He never makes it so any of his characters encounter a mystery that they are not 'involved' with in some way.
For example: The mystery could be about the death of a pop star they admired, thus allowing for subtle characterisation as they work through the mystery using their own 'perspective' of what should be considered the most important clue in the mystery.
If that person is not a airhead but is more of a regular salaryman, then his deductions will be flawed or maybe even too simplistic. However, as a writer who seems obsessed about 'geniuses', there is always one particular person with a high IQ that can put the pieces together in a more convincing way.
This isn't just me gushing about my favourite author though. As I am clearly aware that his style of writing is less suited for thriller-type mysteries and instead focuses on the more 'personal' aspects of it.
A person may find a clue because they can see it from the perspective of a gamer or maybe they'd see it through the lens of a storyteller if they are more of a bookworm. They are deeply personal, but these kinds of mysteries don't have any 'thrilling' aspects that arises from knowledge that time is ticking.
To insert these kinds of moments of tension, there are two requirements that need to be fulfilled for it to work. The first is something the protagonist could potentially 'lose' if he doesn't get something right while the second being properly paced events.
When a scene drags out, tension is built from the answer being found being so close yet still not leaving the tip of the author's tongue. An important moment is dragged with an air of suspense as the reader desperately wishes that the answer they received isn't something that will lead to a more tragic outcome. It is easy to point fingers at people you don't have feelings for, but what is a 'detective' supposed to do when the culprit is a friend?
No one is a logic machine that will choose the prim and proper approach to dealing with such a situation. If the answer that came from eliminating the possibilities is something they can't internally accept, then how would they respond?
It is both a test of character as well as their ability to not be sentimental when determining the cause for an event. Those who link mysteries with the supernatural also have fun with this situation as well. For example: What if the culprit was possessed? Or maybe even blackmailed into it?
This leads to deeper questions than who is the culprit or not and tackles the heart of morality in a cruel way, by forcing the main character to come up with a reply to those questions difficult to answer.
As you can tell, I am very fond of mysteries despite not having dabbled in it myself. As there are many possibilities that can be uncovered from just a simple interaction or maybe even something in the background. There is one more thing I'd like to talk about that has to do with the MC of a mystery.
Let's say the one trying to unravel the mystery isn't Sherlock Holmes one is a person with a exceedingly high IQ. In this situation, how is the main character supposed to figure out a mystery even those around him are unable to solve? The answer to this question is two things: Having help from someone with knowledge but not the perspective needed to put all the clues together in a convincing manner, or making it so the mystery is related to him deeply.
For example: Let's say the culprit is actually the main character's sister. It is of course more easier for him to gain more clues if that's the case since he would have more chances to find evidence on her than anybody else through knowing her intimately.
Finding a way to balance the simplistic aspects of a mystery along with the complexity of events that lead to it becoming a mystery at all in the first place is key. You can't dump great amounts of irrelevant information and expect the reader to be invested into kicking out the 'irrelevant' information in order to find that one answer everyone is looking for.
What a good mystery entails is that the seemingly irrelevant bits of information are put together in ways even the reader should be able to figure out by themselves. Some information can be used as alibis to narrow down the culprit while seemingly unimportant events could increase the suspicion on the person who is truly the culprit in the mystery.
Have fun with trying to write this and be sure to PM me if you have anything else you want an Analysis of.
Have a great day~ 😊