Here’s why murder mysteries are hard to write.
In any other kind of story, we come in at the inciting incident – the point at which the action of the story begins, the point at which the hero’s world is turned upside and she has to take action to save the day. Then we follow her through a gradual process of learning, changing and growing, up to the final decision where she triumphs over adversity/ her enemies and gets what she wants (or more likely, what she needs).
Murder mysteries do not work like this.
A murder mystery has an inciting incident: a body is found, or a person reported missing. They have a denouement: the murderer is caught and the detective’s theory vindicated. But that process of learning, changing and growing, the second act of your story, is missing – because all the significant events in the story have already happened. The victim is already dead, the clues have already been accidentally left or deliberately concealed, the various suspects’ have already done and said most of the things that will make them suspects or eliminate them from the enquiry.
The detective spends the second act finding out about things that are in the past – the dead man’s brother hated him, he’d changed his will, he had an illegitimate daughter, there was a diamond ring missing from the body… So I suppose he’s learning, in the strict sense of the word, but not in the self-revelatory sense in which we use the word when we’re talking about character. The detective can’t change and grow (and neither can anyone else) because nothing is happening to him. He’s just discovering information about historic events, all of which are beyond his ability to influence.
Put another way, a normal drama is like showing a football match from beginning to end. A murder mystery is like explaining why the two teams have to play each other (they’re both finalists in the FA cup, say), showing some flashbacks to previous matches to explain their rivalry, and then showing the last five minutes of the match to establish who wins.
This would explain why many murder mysteries have a second or even third murder during the course of the action, or interweave a subplot about the detective’s work life or home life. It’s current action. Something is actually happening to the character, allowing some level of character development. Because without that, it’s really difficult to sustain a story.
Undoubtedly there are writers who are brilliant at this. They manage to involve us intellectually with the puzzle of the story, and engage us with characters despite the fact that they’re not changing and growing. That’s a real skill, and if you’ve got it, congratulations!
But if you’re having difficulty structuring a detective-style story, as I so often do, perhaps bearing all this in mind will help…