Here’s a good post from Jane Friedman’s blog: Designing Thriller and Mystery Twists That Work
The protagonist’s journey in both thrillers and mysteries is effectively the unveiling of the villain’s plan, as experienced by the protagonist. The protagonist is our (the reader’s) “guide” through the story, because the protagonist is the character leading the reader along as they uncover what the villain was/is ultimately up to.
That’s an interesting way to look at it! The protagonist’s journey is the unveiling of the villain’s plan. I guess that’s true!
Twists are the reveal of the villain’s truth. This truth feels “twisty”, because the reveal of the truth is unexpected to the protagonist. … Satisfying twists are the only logical answer to a puzzle that seemed seemingly impossible to solve as the reader/protagonist moved through the story. Satisfying twists are unexpected, but do not appear out of nowhere. They make perfect sense when the reader looks backwards at what they’ve already been shown on the page via the protagonist and what the protagonist saw, but aren’t easily guessed until they’re revealed because the protagonist led us astray. All the clues were “on screen,” i.e., on the page for us to see the correct answer (the villain’s truth), but those clues were seen (but ignored), or seen (but misinterpreted), or seen (but overlooked) by the protagonist throughout the story.
This is all a neat way to look at this. The protagonist is not your ally! The protagonist is misleading you! Whoops!
Viewed this way, I guess part of the trick is to make the protagonist seem intelligent (even though they are wrong about everything). That can be difficult, and that’s a way a mystery can fail as a mystery even if it succeeds as a story in other ways. I rather like Anne Perry’s mysteries, but in one or another, the physical evidence was quite clear and the only reason the protagonist didn’t realize that was because the murderer was a woman. Even in a historical setting, I don’t think most readers would find that very satisfying or “twisty” today.
The author of this post says: I recommend keeping the protagonist (logically) convinced about a plausible other solution right up until the point they face the truth. This applies to all the main twists: the midpoint twist (at 50%, where the story takes a turn), the climactic twist (at roughly 85%, where the protagonist faces the villain themselves or the person they think is the villain, and restores order) and the final twist (at roughly 98%, where the protagonist uncovers something unexpected, sometimes facing the true villain).
That’s a very beat-heavy, analytical type of suggestion. I guess it’s ideal for formula mysteries if these beats always happen at those points in the story. I would be making a mental note note never to write a mystery or thriller if I thought you always had to follow the beats this closely.
There’s another way a thriller can succeed, though. I mean, a way that has nothing to do with a plot twist, so this departs from the subject of the linked post. But a thriller can be highly successful if the protagonist knows everything early, but keeps encountering obstacles to stopping the bad guy from achieving his nefarious ends. Not sure that’s possible with a mystery, which is one reason, I guess, that I tend to treat them as separate genres rather than lump them together as so often seems to happen, including in the linked post.
Regardless, because the linked post emphasizes that the villain is central and the protagonist’s role is to be misled and then finally uncover the truth, the villain needs to be able to hold up the story.
I’m not a hundred percent sure that’s true. I can think of mysteries where the villain has some very simple motivation and is not a complicated or interesting person. Just wanted Grandma’s fortune early, maybe. That’s simple and boring. The protagonist and everything else going on then take center stage. I’m thinking of Lindsay Chamberlain‘s novels here, especially the one I just linked, though to be fair, there are three mysteries braided together in this novel: the historical one, the contemporary one, and the one where the protagonist is a target. The historical one is the saddest.
Anyway, much more at the linked post about developing the villain and using that as a foundation for everything else:
[O]nce we understand the villain’s actions and motivations, we can lay the protagonist’s journey (solving the mystery/stopping the crime/bringing chaos to order) on top of the villain’s journey. From there, we can figure out the moments their paths intersect, which is key for understanding how the protagonist might misinterpret the villain’s truth.
Even though usually I’m not that interested in the villain’s motivations, I do think this is an interesting and potentially useful way to look at the design of a mystery plot, which is something I’ve always thought looked difficult.