Creating Mystery Characters: Putting the Who in Whodunit

Abi Wurdeman
July 19, 2023

The characters make the mystery.

Sure, the puzzle itself is a good time, but the characters are what make the story memorable.

Your readers only feel that chill because they care what happens to the sleuth. They come back for the series because they can’t get enough of your impossibly clever detective and the unlikely sidekick. They gasp at the twist because they never in a million years would have suspected the beekeeper, but in retrospect, the clues were all there.

Because you did the hard work of crafting characters that make the story feel real and the mystery matter.

If you’re lookin’ to write a mystery and are feeling a little mystified by this aspect of it, don’t worry. You’re about to learn the key elements of mystery character development, including:

  • What character development even means
  • How to create fictional folks that are super compelling to mystery readers
  • How to choose the right arc for your sleuth
  • Common pitfalls to avoid
  • The roles of red herrings and foreshadowing in character development
  • Suggestions for further learning

All shall be revealed in time. By which I mean right now.

The Basics of Mystery Character Development

A hand points a pin at an evidence board.

Character development is the process of turning what’s essentially a chalk outline of a person into a fully realized human being.

In writing, we use the term “character development” to talk about the behind-the-scenes process of creating characters and the way we gradually reveal our fictional people to the reader over the course of the story. 

When you write a mystery, you want to build your characters using the same elements you’d use for any other genre (I’ll share what those are in a sec), but you also have to constantly consider how your sleuth, perp, and suspects all contribute to the overall puzzle of your story.

It sounds like a lot, but we’re going to walk through this nice and slow.

What Character Development Includes

A silhouette of a person with short hair against a pink and blue background.

So what exactly do you need to know about your characters?

We actually have a whole article on that, but here’s the snapshot:

It’s not what I’d call a simple list, but as you may have noticed, there are tons of links leading to articles that make these topics a little less overwhelming.

In a moment, we’re going to talk about how to create some of these character elements for a mystery novel specifically. But before we can dive into the details, we need to get one major consideration out of the way.

Considering the Subgenre

A female noir character in a black leather jacket stands in a doorway holding a gun.

Before you start dreaming up the riveting dynamics between your protagonist and their antagonists, make sure you’re clear on your mystery subgenre. That’s going to influence the way you build this cast of characters. For example:

Police procedural - Your sleuth is a professional detective. They’re probably haunted by something (aren’t we all?). Some folks in your story might be witty or say funny things, but no one is wacky or silly.

Noir - Your sleuth is probably a professional, most likely a PI. They’re deeply flawed, probably self-destructive, and unlikely to change. Many of the characters in their world are gritty, cynical, dangerous, or traumatized.

Suspense - Your protagonist can be an amateur or professional detective—or a retired or disgraced cop. Either way, they’re probably going to be resilient, resourceful, and smart. 

Caper - Lots of colorful characters. Both sleuth and criminal are funny, even if they don’t mean to be.

Cozy - The protagonist is an amateur detective—usually someone who seems like they wouldn’t have a dark enough mind to solve a murder. Tea-drinking senior women are the most popular option. This sleuth is often surrounded by a close-knit community full of quirky folks.

Read current bestsellers in your mystery subgenre to get a sense of reader expectations. When you have the basic gist of it, you’re ready to get into the details.

Creating Compelling Mystery Characters 

Close-up of a human eye.

So how do you make sure your characters aren’t just fully developed but also contribute to spine-tingling story?

Here are a few sneaky little tricks.

Identifying Your Sleuth’s Superpower

Your detective is great at solving crimes—we know that much. But why are they great? What unique talent makes them better at this than everyone else?

Do they have a photographic memory? An uncanny ability to read people? A Super Smeller like Burton Guster?

Identifying what your protagonist is uniquely good at is key in any story, but it’s especially helpful in mysteries. 

For one thing, when your sleuth has a talent for a specific aspect of detective work, you avoid making them too perfect or generically awesome. There’s room for them to make mistakes without compromising your reader’s faith that they can still solve the crime.

Plus, if your reader knows what the sleuth’s superpower is, they can start examining the clues the way your protagonist would.  

Creating Unique Backgrounds

What’s your detective’s backstory? 

An intriguing background can explain why your sleuth is so good at what they do. Do they have military experience that emboldens them in dangerous situations? A psychologist parent who taught them how to read body language to determine a suspect’s emotional state?

Backstory can also explain why your sleuth cares about this case, what’s at stake for them, or what errors they’re likely to make. Have they been kicked off the force for being reckless? Are they haunted by a similar case that they failed to solve before the murderer struck again?

Create relevant backgrounds for other characters, too. Consider your suspects. Is there anything in their past that makes them extra suspicious?

Don’t forget about the victim! The victim’s backstory should be full of clues, including a few that point your detective in the wrong direction. Remember that your victim doesn’t necessarily have to be an all-around innocent person. A victim with a messy past often means there are more people in their life with a believable motive to murder.

Developing Intriguing Character Motivations

A female-presenting person stands in a kitchen, staring off into the distance, as a male-presenting person watches them from a few feet away.

Every major character in a mystery novel is flirting with danger.

The detective is taking on a job they know will put them in contact with criminals. The perpetrator has done something horrifying that could cost them their freedom or even their life. Your suspects may be innocent, but it has to be believable that they could have committed murder (or whatever crime you’re writing about).

Even if your sleuth has a devoted spouse who teaches preschool and spends their free time gardening, that person chooses to live in constant close proximity to crime.

All this to say, everybody in this story needs compelling motivation for pursuing whatever ill-advised goal they’re after. You can find a super helpful guide to character motivation right here. The big idea is that every motivation should be realistic, compelling, and proportionate to your characters’ actions.

In other words, you probably shouldn’t have a character commit a grisly crime because their local grocer stopped carrying pop tarts. You can have them say that’s the reason, but you also have to indicate that something much deeper is going on in their troubled, violent soul.

As I mentioned before, backstory is a great tool for establishing motivation, especially in mysteries. After all, your detective is trying to identify suspects who would have the 1) means, 2) opportunity, and 3) motive to commit the crime. 

Motive is almost always going to show up in a suspect’s backstory. Maybe the victim was blackmailing them. Maybe they always dreamed of making it big on Broadway and the victim was in their way. 

For more on weaving backstory into your characters’ present, check out this article.

Adding Depth to Your Characters With Flaws

Don’t forget to give these people flaws and weaknesses. Perfect characters don’t make for very good conflict. 

Your main character should be exceptional at solving crime, but they need blindspots, deficiencies, and moral failings, too. Let them follow the wrong clue or make a bad call that sets the whole investigation back a month. Toss a little chaos into their personal life, too.

It’s also important that the sleuth has vulnerabilities—something that makes the reader worry about them as they approach that nail-biting climax. Maybe their child is somehow caught in the middle of the investigation. Or maybe they’re planning to confront the killer while being 82 years old (Hello, cozies!). 

On that note, a common weakness for many beloved mystery protagonists is the fact that they don’t seem like the crime-solving, villain-confronting type. In the right situation, this weakness becomes a major strength.

Finally, while you’re loading up your detective with all these failings, don’t forget to give flaws to your other characters, too. After all, someone has to make your protagonist’s life harder. And also commit crimes.

Building Character Arcs

A detective looks at an evidence board.

When we talk about a character arc, we’re talking about the way a character changes—or refuses to change—over the course of a story. 

Mystery character arcs are a little different from the arcs you see in many other genres. Sort of.

The basic principles are the same. You still have characters who confront challenges and change as a result. The basic structure of the arc isn’t any different. (You can learn more about that here.)

What’s different is that in mystery novels, the main character usually doesn’t change all that much. Sometimes they do. But it’s more common for the characters around them to transform over the course of a single novel.

Let me explain.

The Importance of Character Arcs in Mystery Storytelling

Mystery writers usually work with three types of character arc:

Positive arc - A character lands in a challenging conflict that forces them to confront their weaknesses and reconsider their perspective. They change for the better, either morally or in terms of skill. Usually both.

Negative arc - A character’s response to conflict is to change for the worse. They’re total jerks by the end of the story.

Flat arc - A character doesn’t change, even though they might consider it at some point in the story. I don’t know why we don’t just call this “no arc.” A flat arc is just a line. This should be a character line. But no one calls it that, so don’t retain the terminology that makes sense. Just keep saying “flat arc.”

Now, here’s where it gets interesting.

If you were writing a romance or fantasy novel, you’d probably give your main character a positive arc, and seeing that character grow would be part of what sucks the reader in.

In a mystery novel, a lot of the suspense comes from witnessing the positive and negative arcs that happen around the protagonist.

The victim’s sister starts out chill, then acts increasingly erratic until she breaks and reveals a secret that turns the whole case upside down. Or your sleuth’s preschool-teaching spouse decides they can’t be married to a detective anymore after getting kidnapped for the third time. 

So where does that leave your sleuth, arc-wise? Let’s talk.

Choosing the Right Arc for Your Mystery Protagonist

An older, female-presenting person looks over the top of their purple glasses.

Your gumshoe can have any kind of arc you want. That said, you should do some strategic thinking before you commit. Let’s look at how these three types of arcs usually play out for mystery protagonists.

Flat Arc

If you read a lot of mysteries (hopefully you do), you may have noticed that the sleuths who are most likely to have a flat arc are the ones who appear in a series. 

See, when you’re writing an entire series, you have to keep in mind that your readers will get attached to that character as they appear in book one, flaws and all. If your reckless rookie detective undergoes a huge transformation in your first novel, you’re gambling that your readers will be just as charmed when that character shows up as a level-headed rule-follower in book two.

By book three, you’ll have run out of ways for your detective to evolve.

That’s not to say that every sleuth starring in a mystery series has to be too stubborn to change at all. 

Many of these characters appear to have a flat arc when you only see their life one novel at a time. But observe them over the course of eight books, and you realize something has changed. They’ve gotten better at talking to their kid or have become obsessed with one elusive serial killer. (It happens.)

Even if you decide to give your sleuth a pancake-flat arc throughout the entire mystery series, make sure they’re not all emotionless about it. Let them get lonely because their high-risk lifestyle prevents them from starting a family. Let an occasional moment of hope or kindness touch the heart of your die-hard cynic. Give them an internal conflict.

Then let your readers see why your main character believes not changing is the only option.

Positive Arc

You’re more likely to see a positive arc—at least a big one—in a standalone mystery novel. The detective starts with a particular belief or flaw. The external conflict in the story forces them to reconsider their beliefs or overcome a shortcoming. By the end, they’re a better person.

For example, The Searcher tells the story of a recently retired police officer who has zero interest in continuing his detective work. But not only does he get roped into a murder mystery, he also gains a new perspective on what it means to show up in a crisis—a perspective that could heal his fractured personal life. 

Negative Arc

The Searcher’s positive arc is actually a rare occurrence for a Tana French novel. This mystery author has a tendency towards negative arcs when it comes to her detectives. And if you live for chaos and devastation, you might consider this route, too.

In a negative character arc, your sleuth changes for the worse. They might suffer a complete psychological collapse because of the things they’ve seen or succumb to the temptation of corruption, becoming a villain by the end of the story.

We actually have a whole article on negative arcs if you’d like to explore this topic further.

Avoiding Common Pitfalls in Character Development

View from the bottom of a box showing two detectives looking down into the box.

Now you’re all set to write a mystery packed with fascinating characters and artfully crafted arcs. What could go wrong?

Plenty of things. Writing is messy, and you’ll have to go through several drafts before your novel reaches its full potential. But you can make that process just a little bit easier by avoiding these common pitfalls.

Making the sleuth too good - I know we touched on this, but it’s important. Let them miss clues, get sloppy, be difficult to work with… whatever fits the complex character you’ve created.

Hiding crucial character backstory from the reader only - It’s true that in a mystery story, you want to roll out your clues little by little. But if you wait 149 pages to reveal that the victim’s roommate has a reputation for rage, make sure this is the first the detective has heard about it, too. Your reader is the sleuth’s sidekick. Don’t leave them in the dark.

Underdeveloping the perp - Your story’s criminal should be a character your reader feels like they know. Without making the perp’s guilt obvious, give your readers enough opportunities to get to know this person that they feel like they’ve had a chance to consider the true baddie alongside all the other suspects.

Using Foreshadowing and Red Herrings to Develop Mystery Characters

The tools that make for a nail-biting murder mystery can also help you add complexity to your characters.

Think about what it takes to set up a red herring, for example. You have to give a character a backstory that gives them a believable motive for committing the crime. To rule them out, you need to create an alibi, which might give readers an additional glimpse into that character’s life.

Then there’s the thrilling possibility that an innocent suspect is withholding their real alibi. Maybe they’re not particularly proud of what they were actually doing at the time of the crime. Now we’re in the delicious realm of character secrets

In fact, that’s an essential question to ask yourself when writing mystery characters. What are these people hiding? Most of them are probably hiding something.

Foreshadowing is another clever little tool—one that mystery novels make more complicated by turning foreshadowing into its own kind of red herring. 

One character might hint that another character is dangerous, suspicious, or has a secret. Maybe there’s a clap of thunder as your protagonist’s new partner arrives on the scene. Perhaps the mayor warns the amateur detective that digging into this case will create unrest in the community.

These tidbits might guide your sleuth to the answer or simply be distractions. But they all foreshadow the very real inter-character conflict that lies ahead.

Examples of Compelling Mystery Characters

A person lies on a couch reading a book.

Mystery writers learn a lot from each other. So now that you understand what it takes to create fascinating characters in this genre, it’s time to study how successful writers put these principles in action.

Here are some of the best mystery characters out there:

Every Single Character in The Thursday Murder Club Series

…but especially Joyce. 

The Thursday Murder Club is made up entirely of senior citizens who live in the same retirement home and choose to live out their golden years solving crimes, as one does. Every member of the club has a distinct and entertaining voice. So do the professional detectives they work with and many of the criminals they pursue. 

But Joyce—the most chipper and seemingly naive member of the club—is a full-on masterclass in underestimated characters weaponizing their invisibility.

Charlie Cale in Poker Face

Charlie’s sleuth superpower is detecting B.S. She can immediately recognize a lie, and this skill is constantly getting her tangled up in murder mysteries. (That and the fact that people get killed everywhere she goes.)

Plus, Poker Face takes a backwards approach to mystery stories. The viewer learns whodunit early in the episode. The real mystery is how Charlie’s going to figure it out, making this show a great study in weaving the sleuth’s skill set into the suspense.

Isaiah Quintabe in the IQ Series

Isaiah (IQ) is an unlicensed private detective whose whole thing is that he wants to put his exceptional skills to work for his community. His only real resource as a sleuth is his own sharp observations and remarkable intelligence. He’s also willing to accept whatever type of payment his clients can afford.

IQ is a good option if you want to learn about blending extraordinary talent and suspenseful situations with grounded characterization.

Keeping Track of All These Characters

There’s one more thing that makes crafting mystery characters uniquely challenging. You have to keep track of who knows what and where they were with whom on the night of which murder.

I know. Almost too confusing to even conceptualize. But don’t fret; Dabble can help.

On top of its many other features, the Dabble Plot Grid is a-ma-zing for keeping track of characters, subplots, red herrings, clues, and more. It’s designed to show you the entire story at a glance, so you can immediately see what’s working and where the holes are.

Screenshot of a Dabble Plot Grid showing character whereabouts for every scene in a mystery novel.

Plus, you have all your notes (including character notes!) right at your fingertips as you draft your novel.

Want to test drive it for yourself? Go here to snag a 14-day free trial, no credit card necessary. 

Then go turn all this hard-earned knowledge into a mystery masterpiece. 

Whodunit? Youdunit!

Abi Wurdeman

Abi Wurdeman is the author of Cross-Section of a Human Heart: A Memoir of Early Adulthood, as well as the novella, Holiday Gifts for Insufferable People. She also writes for film and television with her brother and writing partner, Phil Wurdeman. On occasion, Abi pretends to be a poet. One of her poems is (legally) stamped into a sidewalk in Santa Clarita, California. When she’s not writing, Abi is most likely hiking, reading, or texting her mother pictures of her houseplants to ask why they look like that.