How to Write a Mystery (From the Author of 90+ Books!)

Writing a mystery looks simple from the outside, but the moment you sit down to plot one, you realize just how many moving parts there are.

It’s not brain surgery, but it does require forethought, careful planning, and a sense of timing. That’s one of the reasons the genre has a reputation for being tricky to pull off.

Think of this article as a quick-start guide to mystery writing. Of course, no single blog article can capture every nuance of the craft (unless your name happens to be Agatha Christie or Sir Arthur Conan Doyle).

But there are several core elements you’ll need to nail if you want your readers to feel that satisfying “aha!” at the end.

Here’s what we’ll cover:

• Choosing the right antagonist
• Building believable motivations
• Planting red herrings that actually work
• Weaving together your main plot and subplots
• Common pitfalls to avoid

Disclaimer: Just so you know where I’m coming from, I primarily write cozy mysteries with a small-town flavor. That said, the principles here apply across the spectrum, whether you’re tackling hard-boiled, police procedural, or anything in between.

Step 1: Craft Suspicious Characters

Creating compelling characters is a must in any story. In mysteries, though, you get to add an extra twist: suspicion.

That’s where the fun comes in. Mystery thrives on uncertainty… on the possibility that even the most ordinary person might be hiding something. Think of the sweet neighbor who suddenly seems capable of terrible things, all because they had something to gain.

When you’re building your cast, assume that every character (except your protagonist) should carry at least a faint shadow of doubt.

A single suspicious character makes it too easy for readers to guess the culprit. But a web of potential suspects (each with their own secrets, flaws, and motives) keeps readers guessing until the last chapter. Those “I didn’t figure it out until the end!” reviews? They come from stories where suspicion was spread around effectively.

Your protagonist is the exception.

They need to be credible, relatable, and anchored in the reader’s trust. That doesn’t mean they’re perfect (they’ll still need real flaws and growth), but readers shouldn’t seriously wonder if they committed the crime.

What your protagonist needs:

• Conflict and stakes. For example, maybe your sleuth is rebuilding their life after a major setback. When someone dies under suspicious circumstances in their orbit, they risk losing everything they’ve worked for if the truth doesn’t come out.
• A clear goal. Their drive to solve the mystery should be tied to their personal struggle. In uncovering the crime, they’re also forced to confront something internal.
• A growth arc. By the end, they should be changed. Solving the case not only resolves the external mystery, but pushes them forward in their own life.

Once your main character is set, it’s time to fill the stage with suspects. This is where you can let your imagination roam.

How to build your cast of suspicious characters:

• Start with a diverse list. Mix in different personalities and roles. A colleague, a rival, a neighbor, a friend… the variety makes the puzzle richer.
• Give each suspect a goal. Maybe one wants professional recognition, another wants revenge, another wants money. Keep the motives believable but varied.
• Layer in flaws. A character’s weaknesses should raise questions. Someone who lies easily, cuts corners, or hides a shady past will always seem like they could be capable of worse.
• Establish rivalries. A suspect with a clear enemy instantly gains an extra layer of tension. Rivalries create built-in conflicts that fuel red herrings and subplots.

As you do this, you’ll find that each character has a believable motive for murder (or at least for looking guilty).

Some may end up being crucial to the central mystery, while others serve as distractions or side stories that enrich the world. Either way, readers will enjoy trying to puzzle out who they can actually trust.

Step 2: Decide on Who’s Dying, Why and How

One of the central decisions in any mystery is choosing the victim.

That choice ripples through the entire plot: who notices their absence, who benefits, who looks guilty, and what questions the reader will ask.

In cozies the victim is often someone nobody will mourn (which multiplies suspects and gossip), but you can pick anyone on your character list. What matters is having a clear, believable reason they were targeted.

Think about the victim’s role in the community and how they intersect with other characters’ needs and fears.

Were they owed money? Keeping a dangerous secret? Harassing an ex?

Those hooks create motive, and motive generates suspects. You’ll write all this background into your notes, but you won’t hand it to readers all at once. You’ll reveal it in pieces as the plot demands.

How the murder happens matters almost as much as who is killed. The choice of method can become a clue (or a red herring) and should feel consistent with the world you’ve built.

If you use poison, research its effects and timing; if it’s a firearm, think about wounds, range, and forensics; if it’s a staged “accident,” work out what would look accidental to police and what wouldn’t. Mystery readers notice mistakes, so do the homework… but don’t let technical detail overwhelm the human drama.

Also think practically: who had the opportunity?

A clinic receptionist might have access to pharmaceuticals; a chef could handle food easily; a groundskeeper might know where a shovel is buried. Tying the method to believable access creates strong narrative logic and it gives you a tidy way to plant clues and misdirections.

Actionable steps

1. Pick the victim. Decide which character’s death will best drive the story and raise stakes for your protagonist.
2. Write the motive. Note why they were killed and how that connects to several other characters’ wants and needs.
3. Choose the method and research it. Make sure the effects, timing, and practicalities of the method you pick hold up under scrutiny.
4. Map opportunity. Give a handful of characters plausible access to the weapon or means. This creates the pool of suspects.
5. File the facts (but don’t reveal them all). Keep a private dossier of who, why, when, where, and how you can pull from when planting clues.

A small-town pastry feud, a stolen recipe, or an argument over a property line… any of those everyday conflicts can become the hinge that turns motive into murder.

Use ordinary details to seed believable reasons, then let your plot reveal them in the right order so readers stay guessing until the last page.

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Step 3: Pick an External Conflict

This is kind of an optional step. It depends on how long your mystery is going to be. In cozy mystery, books usually range from 20,000 words to 70,000. If you’re writing a longer story, you’ll need more intrigue, more conflict, and more plot.

This is why I’ll generally pick out an extra external conflict to include in the story. Say we use Jessica’s bakery as an external conflict–she’s being stolen from and things have been going missing in her apartment above the store. What could it mean?

The theft and the murder can be unrelated, or they can be part of the same motivation for the death of the victim. That’s up to you to decide. You can include several sub-plots for characters who Jessica is friends with too.

Perhaps, her new friend is being stalked, or has recently come into money and some of it has gone missing. Or she’s just broken up with an ex-boyfriend, who keeps threatening revenge on the bakery. All of these subplots add up to equal little clues.

The trick is to make the clues of one subplot connect with the main murder mystery. For example, Jessica is suspicious of the theft in her store, and when someone breaks in and steals her journal, she’s not sure if it’s the thief or the murderer.

Important to note: you don’t have to tie off every subplot with a neat ending as you close the book. You can leave some of them open for further exploration in the series. But, you should always give the murder mystery a satisfying conclusion, and your protagonist resolution of their current conflict or goal. Jessica has saved her bakery, she throws a party with her friends afterward to celebrate.

Actionable steps:

1. Write up a list of external conflicts you want to use in your story and how they connect to each character.
2. Pare the list down to one or two subplots.

Step 4: Write up a List of Clues

Another fun step!

Here, you get to write down all the clues that pertain both to your subplot and your main plot. You’ll do this by identifying the crime scene and the clues that are already present there. Since you have the inside edge–you know why your victim was killed and by whom–you can plant evidence over the course of the story that will redirect your protagonist.

You can also plant false evidence, or clues that make it seem like someone else commited the murder. These are called ‘red herrings’ — and they must be believable. All your clues and red herrings have to make sense, after all.

Motivations and clues tie in with each other. Granny wants to get into Jessica’s bakery, so it would make sense that Jessica would walk in on Granny rummaging through her things. Granny can make an excuse, but Jessica will have her suspicions–is Granny the murderer? We know Granny isn’t, but Jessica doesn’t–that’s a red herring that makes sense.

And now, because Jessica believes that Granny might have something to do with the murder, she’ll start following her and unraveling more of the mystery that is Granny’s motivation. Ultimately, she’ll hit a brick wall when she realizes that Granny can’t possibly have commited the murder… until Granny gives her another clue that leads Jessica onto the next suspect.

Actionable steps:

1. Write down a list of clues that connect the characters to the crime scene or make them suspicious.
2. Organize the clues in the order you want them to happen. (i.e. Jessica finding Granny in the bakery after hours. Jessica follows Granny and finds her meeting with Jessica’s enemy etc.)
3. The list doesn’t have to be exhaustive, but it must make sense and tie into your murder and sub-plots.

Step 5: Outline Your Story

I’m not going to go into the outlining process in full here because that would take another article’s worth (and more) of information. However, if you’ve followed the steps above, you’re halfway there. You just need to organize your clues into an events list, and then have your protagonist take action throughout the story.

Let’s look at our example of Jessica and her bakery.

The basic idea is to note down the following:

1. Jessica’s conflict and goal.
2. Her external conflict.
3. An events list of what happens.
4. A short scene or chapter-by-chapter breakdown.

We already have Jessica’s conflict and goal, as well as her external conflict. Now, we need an events list that ties in with all of the above. An events list is a short breakdown of what happens over the course of the three-act story. The events are important plot points that drive the mystery forward.

• The inciting event. This is what starts off your entire mystery. Jessica’s customer drops dead after tasting her cupcake.
• The first act climax. Here, Jessica believes she’s closer than ever to solving the mystery–thus casting her back into her comfy ‘not trusting anyone zone.’ Jessica finds a clue that leads her to believe Granny is the murderer.
• The midpoint reversal. At this point, your character’s goal is flipped. Where Jessica didn’t want to trust anyone before, now she has to. Jessica snoops in a suspect’s house and gets caught. She’s arrested and has to rely on her friend to bail her out.
• The second act climax. Things get even worse. Jessica is completely stumped. She’s been reprimanded and her bakery is no longer popular because of the suspicion that she’s murdered the victim. At the end of this period of sadness, Jessica will discover or connect two clues together that she hadn’t before. Now, she really knows who did it.
• Climax. Here comes the building action and climax of the plot as Jessica faces off against the real murderer.

There’s a denouement–a resolution–as well, where Jessica and her friends celebrate their victory. Jessica will have resolved her conflict. She now loves the town and its people, and trusts her friend. Her bakery is also doing fine again.

After deciding on your events, you’ll pepper them with your clues and find unique ways to solve the mystery and tie the subplots into it.

Bonus Step 6: Mystery Don'ts

Don’t fall into the trap of relying on easy fixes in mystery stories. The readers in this genre are voracious, and they enjoy being challenged. They want you to keep them guessing until the end.

Here are a few mystery don’ts to bear in mind when writing your story.

• Don’t make it too obvious. Readers don’t want to figure out who did it in the first few chapters. They’ll stop reading the book.
• Don’t bore your reader. Don’t use too many unnecessary details or backstory elements that don’t matter. Intrigue is the key. Less is more.
• Don’t provide too much information. You want to pepper in those clues, not have two per chapter — otherwise you’ll overwhelm your reader with information, some of which doesn’t pertain to the murder mystery.
• Don’t provide too little information. You don’t want your reader to feel cheated. Give them enough clues to try to work out the mystery by themselves, but be clever about it. You don’t actually want them to solve it before you do.
• Don’t murder someone too late. Murder mysteries need to have a dead body somewhere near the beginning of the story. It doesn’t have to be in the first chapter, but you’ll need it somewhere close to the front of the book. Foreshadowing is your friend.

How to Write a Mystery: Final Word (or is it??)

If you’ve worked through these steps, you’ve already laid the groundwork for a mystery readers won’t want to put down.

The final piece is practice — both in your own writing and by reading widely in the genre. Every author brings a different rhythm to suspense, a different way of planting clues and misdirection.

The more mysteries you read, the sharper your instincts will become for what works and what falls flat.

Pay attention to the choices other authors make (from crime scene setups to character reveals) and let that inspire (but not dictate) your own style.

Most of all, enjoy the process. Writing a mystery isn’t just about tricking readers; it’s about inviting them into a puzzle only you can create.