I’m writing from a farm in Tennessee right now, a little less than halfway through a week-long writing retreat. It. Is. Great. It’s amazing how much writing I can get done when it’s my only job.
The story I’m working on is essentially a murder mystery in the clothes of a fantasy novel (which, minus the “murder”, is also true of most Harry Potter books, in case you didn’t know.) Mystery is probably the genre I read the most, and I’ve always known I was going to write one someday — but the idea of plotting one was daunting.
There are a lot of plot outline templates for novels, which give you a layout of what beats to hit when, which is the kind of thing that’s hugely useful to me. But I needed something specifically for mystery, and something that could be adapted to a very different setting than the classic real-world investigative whodunnit. I started working out my own theories, and halfway through doing that I found this Two-Body Plot breakdown by John P. Murphy.
Below, I’ve basically taken the two-body plot as described by Murphy, and thrown in my own take at a couple of points. I think it’s a pretty good act framework for a mystery, and is certainly what I’ll be using for my first stab at outlining.
Act 1: the characters are introduced: the eventual suspects, killer, and victim, and sometimes also the detective. Conflicts and tensions that hint at the murder motive, as well as some red-herring motives, are presented. If the detective has personal issues to work out in this story, they come up here too. The reader should be getting invested in either the detective’s situation, some of the characters’ conflicts, or just in trying to guess who’s going to be killed and why (I always do this if I know I’m reading/watching a murder mystery — if your readers aren’t likely to know that, though, you need to build tension in one of the other ways.)
Act 1 ends on the discovery of the initial victim, which pivots us into the investigation.
Act 2: Early-stage investigation. The detective and reader are scoping out the terrain of suspects, motives, and clues. During this act we should be rapidly piling up questions in addition to the main “whodunnit” question. Why did Sally go visit Jane in the middle of the night? Who moved the teakettle from its usual place? How could someone have gotten to the fifth floor of the building? What are suspects X, Y, and Z hiding?
Act 2 ends on the discovery of something that dramatically alters the tone of the investigation. In the original essay it’s another body, but I think a major reveal (“Jane is secretly Sally’s mother, and Sally had no idea!”) can serve the same role. Even if it’s not a corpse, it should represent some kind of failure or disaster for the detective: their main working theory disproven, the person they love suddenly implicated, something like that.
Act 3: Late-stage investigation. The stakes are raised by the Act 2 corpse/reveal; the detective is more emotionally invested and driven. Where in act 2 we raised more questions than answers, here we should be getting answers in pretty quick succession — but answers that create additional questions, or tension or danger. Often there’s something in place to put time pressure on the solving: fear that the killer will strike again, a suspect the detective who’s in growing danger of being arrested although the detective believes they’re innocent, the risk of the detective being taken off the case. In general things are moving much more quickly, and with much more tension, than in act 2.
Act 3 ends with the big reveal. The reveal scene needs to be very tense, dramatic, and exciting, even though ultimately the reveal can be expressed in three words: “X did it.” There are two time-honored ways of doing this. You can create some action around the scene: a chase, a third murder attempt narrowly averted, a life-threatening trap the detective walks into. Or you can assemble all the suspects in a room and let the tension come from everybody’s suspicion of each other, and the slow unpeeling of secrets by the detective.
In the denoument (Act 4 in the original scheme) you answer any unanswered questions, resolve the relationships of the remaining characters, and sort out whatever personal consequences the detective faced. Mystery readers want to walk away with everything tucked neatly to bed, with the possible exception of some personal arc for the detective that will carry over into the next book.