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A whodunit, a popular form of detective fiction, is a mystery story that starts with a crime, such as a murder, a theft, or a kidnapping. The focus of the whole story is on the motives and identity of the criminal, which are only revealed at the very end.
A whodunit constructs a puzzle around solving the crime. The who, what, when, where, and why of the crime are slowly revealed throughout the story.
So, how do you write a believable whodunit that shocks and excites your reader?
This article covers the characters your whodunit needs, how to write a great twist, and what to include in each of the four acts.
Who’s in Your Whodunit?
Mystery readers love puzzles, but they still want to connect with the characters.
Build a solid cast of characters to emotionally connect your reader to the story. In order for readers to feel involved in solving the crime, they need to care about the people involved. Your characters drive reader engagement.
Readers expect to find certain characters when reading whodunits. Here are a few common character archetypes.
The victim of the crime is the fulcrum around which the rest of the story pivots. Without them, there’s no whodunit question. Your victim connects to all the suspects, including the villain.
Your entire story leads to the revelation of the villain. As cunning, clever, and intelligent as your detective, the villain builds smoke screens and creates false trails that puzzle the reader and your sleuth.
Your sleuth is the reader’s guide to solving the puzzle. Whether professional or amateur, their goal is to find out “whodunit.”
Your detective has a strong personality and, like any protagonist, takes action. Create strengths and weaknesses to make them relatable and engaging.
Suspects have a connection to the victim. Each suspect tests your sleuth’s skills in discovery and deduction.
They each have a unique personality which tests your sleuth, and the interactions between the detective and the suspects are the meat and potatoes of your story.
One of the suspects eventually turns out to be the villain, but the set of suspects creates the puzzle for your sleuth and your reader to solve.
Supporting characters enhance your sleuth’s world. They add dimensions to your protagonist and to the story. These run the gamut from sidekick to love interest.
You may add a guiding mentor or a jealous colleague. Every interaction your protagonist has with supporting characters enlarges the story.
Create a character bible to keep track of all the characters in your mystery, even the minor ones.
Fill in each character’s background with personality traits, unique dialogue phrases, and patterns. Know how each character relates to the other characters and their role in the story. Once you have a good grasp of your characters, you can refer back to your character bible for details as you are writing.
Twister for Whodunit Plots: Quick Tips
Every great whodunit story needs a twist. A good twist should shock, intrigue, or amaze the readers, without annoying, confusing, or frustrating them.
But reaching this balance can be tricky, so here are three quick tips for writing a great plot twist your readers will love.
Drop subtle clues: The best twists are the ones where your reader thinks, “I should have seen that coming.” Include foreshadowing to give them clues along the way.
Subvert expectations: Common twists are easy to see coming and can be disappointing. Put a spin on common plot twists to keep your readers guessing.
Make it plausible: Your twist should make sense and be plausible. You don’t want your reader to feel tricked by a twist that has come out of the blue.
Pacing Is Key
Even if your plot is gripping, your reader will get bored if your pacing is wrong.
When you’re wrapped up in the mystery, it’s easy to dive too deep into the details. Make sure you’re varying your exposition, action, and dialogue with ProWritingAid's Pacing Report.
ProWritingAid can highlight your slower-paced paragraphs so you can make sure you’re getting all of the detail across without losing your reader.
Let's take a look at the story beats you can use in the plot of your whodunit.
Act One: Set Up and Complicate
Act One is about bringing your reader into the story. In a mystery, you introduce the reader to your sleuth and, usually, the murder.
One of the best ways to introduce your sleuth is to show them solving a problem. This shows your readers your sleuth can do what they’ll need to do to find the murderer.
Illustrate at least one of your sleuth’s key strengths early in the story. If you know how they will catch the villain, mirror that talent in the beginning.
Once your reader knows your sleuth and sees them in action, something happens that triggers your story.
The Inciting Incident
Move your sleuth out of their everyday world into a new challenge. In this scene, present them with a challenge they didn’t see coming.
Something happens that pulls your sleuth toward the main mystery. It could be a new neighbor, an old lover, a vehicle breakdown, or anything you want to imagine.
Although your sleuth (and your reader) doesn’t know it yet, this small disturbance in their regular life is leading them toward the big mystery.
Once you introduce this event and show your sleuth’s reaction, it’s time to meet the mystery head on.
The First Plot Point
Now you introduce the dramatic event that must be answered in the climax of your story. At this point, the sleuth is brought in or volunteers to find the killer.
How this event unfolds will depend on the type of mystery you write. A cozy heroine may take on the search, or a cop may be assigned to solve the crime. Either way, your detective enters the mystery and takes on the challenge of solving the puzzle.
Act Two: Conflict and Rising Action in Discovery
Now your sleuth must poke and probe to learn about the victim and the murder. They examine physical evidence and build a list of possible suspects.
In this section of your mystery, your sleuth gets to know the victim’s world—what the victim did, who the victim spent time with, and why the victim was where they were when they were murdered.
Act Two is also the right time to introduce any subplots. Perhaps the sidekick has a problem, your sleuth meets a love interest, or outside forces put extra pressure on them.
Things aren’t going smoothly with the case, either. A piece of evidence is lost, or your sleuth misinterprets (for now) its significance.
Challenge your sleuth at the pinch point. Whatever they think is the right approach doesn’t work.
Your sleuth is nowhere near discovering who the killer is. During this discovery phase, throw in as many complications as you can. Each suspect should have their own personal reasons for resisting and not fully cooperating.
Make each complication more challenging than the last. More complications mean more tension and more tension keeps readers guessing and turning pages.
The Midpoint (also called the Second Plot Point)
The midpoint comes between Act Two and Act Three. This is when the story pivots in some crucial way.
Your sleuth may discover that they’ve been going down the wrong path and start to rethink everything. Or they may find out a crucial piece of information that takes them in a new direction.
Act Three: Crisis
After the midpoint, your sleuth looks for an alternative approach to solving the puzzle, and it doesn’t go well. Your sleuth must reexamine everything they learned in Act Two.
You can add even more complications and twists to the subplots here.
Second Pinch Point
The second pinch point shows your sleuth that the new direction they chose after the midpoint will not get them the results they want. The undiscovered villain may set a trap that confuses your sleuth. Your sleuth realizes they’re in over their head.
Now your sleuth must gather forces. They may find new support, discover new evidence, and somehow get closer to discovering the murderer.
Your sleuth examines all the old evidence with new information and a fresh approach. They’re looking for the evidence or suspect statement they overlooked before.
Now that they’re on a new discovery path, your sleuth feels closer to catching the killer.
Third Plot Point
The killer uses a smoke screen and everything the sleuth thought they knew leads nowhere. Your sleuth needs to clear their vision of the victim’s world and take a new approach.
Act Four: Climax
Your detective is captured or blocked from finding the killer. The victim’s world becomes more of a mystery.
Your sleuth is just not seeing anything the right way. If they’re trapped or captured, there’s no way out.
At last, your sleuth sees a way out. After the escape from the trap or block, they start rethinking and get a glimpse of who the killer might be.
But there’s still something that isn’t clear. They get ready to confront the killer, but there’s one last defeat, and it’s the biggest of all.
Your detective knows the killer is dodging but can’t get to that final confrontation.
And when your detective finally finds the killer, the killer has a surprise in store. Your detective may have made a false assumption or misread the killer’s intent.
The killer pulls out one last trump card, one the detective didn’t expect. Whether it’s a battle of wits or hand-to-hand fighting, the killer plays that one last card.
Your detective finally realizes how to confront the villain and challenges them face to face. At this point, your sleuth reveals the murderer. In addition, your sleuth shines the spotlight on their special skills that led them to this final confrontation and revelation.
In the midst of all this rising action, bring each subplot to a conclusion because once your sleuth reveals the killer, you’ve finished your unwritten agreement with your reader to solve the puzzle.
Revelation and Conclusion
Once your sleuth has revealed the villain, wrap up your mystery. When the killer is revealed, bring your story to a quick conclusion.
A Discovery Journey
A straightforward way to approach a whodunit is in two parts: the beginning and the ending.
Before the middle, the story expands. The reader receives clues, evidence, and information on potential suspects. After the middle, the story contracts. Your sleuth eliminates false clues and suspects one by one until the logical conclusion is the villain.