How to Write a Mystery Novel, Step by Step

To write a mystery novel, decide the crime and its solution first, build a small circle of suspects who each have a motive, the means and the opportunity, give a detective the job of finding the truth, plant the clues fairly where the reader can see them, and end with a reveal the reader could have reached alone. A mystery is written backwards: the author knows the answer before page one, and the book is the route the detective takes to it.

The nine steps below take that in order. The rules behind them come from the people who shaped the genre: Edgar Allan Poe, who wrote the first Dupin story in 1841; S. S. Van Dine and Ronald Knox, who wrote down the fair-play rules in 1928 and 1929; Raymond Chandler, who argued with them; and P. D. James, who summed the form up in 2009. Every quote was checked in the original text.

What Makes a Novel a Mystery?

A crime, a question and an answer. P. D. James gave the classic definition in Talking About Detective Fiction (2009):

"What we can expect is a central mysterious crime, usually murder; a closed circle of suspects, each with motive, means and opportunity for the crime; a detective, either amateur or professional, who comes in like an avenging deity to solve it; and, by the end of the book, a solution which the reader should be able to arrive at by logical deduction from clues inserted in the novel with deceptive cunning but essential fairness."

That one sentence holds the whole structure: the crime, the suspects, the detective, the clues and the solution. Everything in this guide is one of those five parts.

The question matters as much as the crime. A mystery is what Orson Scott Card calls an idea story, and in How to Write Science Fiction and Fantasy (1990) he gives its shape: "The Idea Story begins by raising a question; it ends when the question is answered." A mystery that answers its question in chapter 30 and keeps going for ten more chapters has ended without telling the reader. The four kinds of story, and why their endings differ, are set out in the MICE Quotient.

What Are the Steps to Write a Mystery Novel?

1. Choose the kind of mystery.
2. Plan the crime and its solution first.
3. Create the detective.
4. Build a closed circle of suspects.
5. Plant the clues and the red herrings.
6. Plot the investigation.
7. Write the reveal.
8. Play fair with the reader.
9. Write to length and revise.

Step 1: Which Kind of Mystery Are You Writing?

Choose the kind first, because it decides who investigates, how much violence is on the page and what the reader expects at the end.

Kind	Who investigates	What readers expect
Classic whodunit	A brilliant amateur or a private consultant	A puzzle, a closed circle, a gathering for the reveal
Cosy mystery	An amateur in a small community	Violence off the page, a likeable sleuth, a series
Private eye (hard-boiled)	A professional detective for hire	A city, moral grey, the detective's own code
Police procedural	Police officers	Realistic method, teamwork, more than one case at once
Historical mystery	Any of the above, in the past	Period detail that matters to the solution

A mystery is not the same as a thriller. In a mystery the question is who did it and why, and the crime usually happens near the start. In a thriller the question is whether the hero can stop it, and the danger is still ahead. Many books mix the two, but the balance tells the reader which kind of suspense to expect.

Step 2: Why Should You Plan the Crime First?

Because the solution decides every clue. Poe knew this about his own Dupin stories. In a letter to Philip Pendleton Cooke on 9 August 1846 he called them "tales of ratiocination" and was frank about how they work: "In the 'Murders in the Rue Morgue', for instance, where is the ingenuity of unravelling a web which you yourself (the author) have woven for the express purpose of unravelling?"

That is the method. Weave the web first. Before you draft, write down:

• What really happened. The crime, minute by minute, from the culprit's side.
• Who did it and why. A motive the reader will believe.
• How they did it. The means, and how they hid it.
• What they did afterwards. The lies and the cover-up, which are where most clues come from.

Raymond Chandler put motive first. In his "Twelve Notes on the Mystery Story", printed in The Notebooks of Raymond Chandler (1976), his first note is that a mystery "must be credibly motivated, both as to the original situation and the denouement; it must consist of the plausible actions of plausible people in plausible circumstances". In "The Simple Art of Murder" he praised Dashiell Hammett because he "gave murder back to the kind of people that commit it for reasons, not just to provide a corpse".

Step 3: How Do You Create a Detective?

Give the detective a reason to investigate, a method of their own and something to lose. Van Dine's sixth rule is the minimum: "The detective novel must have a detective in it; and a detective is not a detective unless he detects." The detective's job is to find and read the clues. If the answer arrives by luck or by confession, the book has no detective in it.

Then choose the detective's distance from the crime:

• An amateur has a personal reason to care: a friend is accused, or a body turns up in their shop. The reader learns the method alongside them.
• A professional has a job to do and the access that comes with it. Their story is often about the cost of doing it.

Chandler wrote the best-known portrait of the private eye at the end of "The Simple Art of Murder": "But down these mean streets a man must go who is not himself mean, who is neither tarnished nor afraid. The detective in this kind of story must be such a man. He is the hero; he is everything."

A companion helps too. Ronald Knox's ninth rule, from 1929, describes the Watson role: "The stupid friend of the detective, the Watson, must not conceal any thoughts which pass through his mind; his intelligence must be slightly, but very slightly, below that of the average reader." The point is not that the friend is foolish. A narrator who sees what the reader sees, and says what they think, lets the reader compete with the detective on equal terms.

Step 4: How Many Suspects Should a Mystery Have?

Enough for real doubt, few enough for the reader to keep track: usually three to six. P. D. James calls it "a closed circle of suspects, each with motive, means and opportunity for the crime." Closed means the culprit is inside the circle. A stranger who appears in the last chapter is not a solution.

For each suspect, work out:

• Motive. Why they might have wanted it done.
• Means. Whether they could have done it: the strength, the skill, the poison, the key.
• Opportunity. Whether they were there, or could have been.
• A secret. Something they are hiding that is not the crime. This is what makes innocent suspects lie, and lies are what make them look guilty.

The culprit should be someone the reader knows. Van Dine's tenth rule: "The culprit must turn out to be a person who has played a more or less prominent part in the story". Knox's first rule says they must be "mentioned in the early part of the story". How to hide that person in plain sight is the subject of how to write a plot twist, and a culprit with a real goal of their own is easier to write once you know what makes a good villain.

Step 5: How Do You Plant Clues in a Mystery?

In plain sight, without pointing at them. Chandler's third note is the clearest rule on this: "It must be honest with the reader. This is always said, but the implications are not realized. Important facts not only must not be concealed, they must not be distorted by false emphasis. Unimportant facts must not be projected in such a way as to make them portentous."

In practice:

• Bury each clue in an ordinary scene. A clue in a scene about something else is visible but not loud.
• Use more than one kind. Physical clues (a stopped watch), testimony (a lie about the time), behaviour (a suspect who changes the subject) and absence (the dog that did nothing in the night, in Conan Doyle's "Silver Blaze").
• Plant at least three clues to the truth, spread through the book, so the answer survives a reader missing one.
• Give every red herring an innocent explanation. A red herring is a clue that points the wrong way. When the truth comes out, the reader should see why it looked bad. How Conan Doyle and Christie built theirs, and where the term comes from, is set out in what a red herring is.

Van Dine's first rule sets the standard: "The reader must have equal opportunity with the detective for solving the mystery. All clues must be plainly stated and described." Every clue is also a promise the ending has to keep, which is the idea behind Chekhov's gun; and a hint that only makes sense later is foreshadowing by another name.

Step 6: How Do You Plot a Mystery Novel?

Plot the investigation in rounds, each one changing what the detective believes. A common shape:

1. The crime. Early, often in the first chapter. Van Dine's sixth rule speaks of "the dirty work in the first chapter". If the body arrives late, open with a question that pulls the reader in until it does.
2. The first round. The detective meets the suspects, and each one lies about something.
3. The turn. Around the middle, a discovery changes the case: a second crime, an alibi that collapses, a suspect cleared.
4. The second round. Narrower and more dangerous. The detective follows the real clues, often without knowing which ones they are.
5. The crisis. The detective is wrong, or in danger, or both.
6. The reveal. The truth, and the proof of it.

Keep the pressure on. Chandler, looking back at the pulp magazines in his 1950 introduction to The Simple Art of Murder, said the demand was for constant action: "When in doubt, have a man come through a door with a gun in his hand. This could get to be pretty silly, but somehow it didn't seem to matter." He was describing a habit, not recommending it. The better fix for a slow middle is a new fact that changes the case.

A subplot, such as the detective's family or a romance, can run beside the investigation. It works best when it collides with the case, as how to write a subplot explains.

Step 7: How Do You Write the Reveal?

Let the detective reach the answer by reasoning from the clues the reader has already seen. Van Dine's fifth rule: "The culprit must be determined by logical deductions", not by accident, coincidence or a confession that comes from nowhere.

A good reveal does three things:

• It names the culprit, a familiar figure the reader had stopped suspecting.
• It shows the proof. The detective walks through the clues, in order, and the reader sees each one again.
• It explains the red herrings. Every innocent suspect's lie gets its reason.

Keep it short. The reader wants the moment of understanding, not a lecture. After the reveal, give the story a page or two to settle: what the crime cost, and what changed for the detective.

Step 8: What Are the Rules of Fair Play?

They are the promise that the reader could have solved it. Van Dine's twenty rules (The American Magazine, September 1928) and Knox's ten (1929) set them down. The Detection Club, formed in 1930, whose members included Knox and Agatha Christie, made new members promise that their detectives would solve crimes by their own wits, not by coincidence or divine revelation. The core of every list is the same:

• The culprit is someone the reader meets early.
• Every clue the detective uses is shown to the reader.
• No supernatural help, no lucky accident, no secret poison unknown to science.
• The answer comes from the clues, not from a confession.

Some of the old rules were taste, not fairness. Van Dine's third rule, "There must be no love interest", has been broken by a great many good mysteries. Christie's The Murder of Roger Ackroyd (1926) breaks what became Knox's first rule three years before he wrote it, and the book is still a classic, because every sentence its narrator wrote was true. The fair-play rules, and how a twist can break one and still play fair, are set out in full in how to write a plot twist.

Step 9: How Long Should a Mystery Novel Be?

It depends on the kind. The Mystery Writers of America defines a full-length cosy mystery as 65,000 words or more for its Lilian Jackson Braun Award, and the figures for each publisher are on cosy mystery word count. Crime fiction that leans towards suspense runs longer, as thriller novel word count sets out.

Then revise in two passes. Read once as a reader, for pace. Read once as a detective, for fairness: list every clue, where it is planted and where it pays off, and check that each one appears before the reveal. A clue that only appears in the explanation was never planted. Reading the draft for plot holes catches the rest: an alibi that changes, or a time that does not add up.

A Worked Example

Here is the plan for a short mystery, The Tide Clock.

• The crime: Edwin Hale, the harbour master, is found drowned under the pier at dawn. Dr Alder says he fell in drunk.
• The detective: Ivy Cole, the postmistress, who knew Edwin never drank after nine.
• The truth: Dr Alder, treasurer of the lifeboat fund, has been taking its money. Edwin found out and was going to the committee. Alder met him on the pier at half past eleven and pushed him in.
• The suspects:

Suspect	Motive	Means and opportunity	Secret
Tom Hale, nephew	Inherits the boatyard	Quarrelled with Edwin; no alibi after eleven	He was meeting a girl her father has forbidden him to see
Gwen Price, innkeeper	Edwin knew about her smuggled brandy	Served his last drink	The brandy
Dr Alder	Edwin found out about the fund	Says he was at a farm inland all night	The fund, and the murder

• Scene 1, the body under the pier. The crime, and the doctor's easy answer.
• Scene 2, Tom's quarrel. Red herring: the nephew fought with Edwin at the inn and inherits everything.
• Scene 3, the stopped watch. Clue: Edwin's watch stopped at 11.40 when it hit the water. Alder says he saw Edwin alive on the pier at midnight.
• Scene 4, the brandy. Red herring: Gwen lies about the time Edwin left. She is hiding the brandy, not a murder.
• Scene 5, salt on the boots. Clue: Alder's boots are white with dried salt. He says he spent the night inland.
• Scene 6, the ledger page. Clue: a torn page from the lifeboat fund ledger, in Edwin's coat. Alder keeps the ledger.
• Scene 7, the reveal. Ivy lays out the watch, the boots and the page. Tom's quarrel and Gwen's lie each get their reason.

The culprit is in the first scene, offering the answer everyone accepts. Each suspect has motive, means and opportunity, and each innocent one has a secret that makes them lie. The three real clues come before the reveal, in three different scenes, and none of them is pointed at: the watch is about the time of death, the boots are about the weather, and the ledger page is about Edwin's paperwork.

How Do You Plan a Mystery Novel in Deckle?

Deckle is a novel-writing app for Windows, macOS and Linux. Its Codex holds characters beside the manuscript, and its Outliner is a board of cards, one for every document in the book, each with a synopsis. Together they hold the suspects, the clues and the order the reader meets them in.

1. Open the Codex from its button in the menu bar. In Characters, click the + (New entry) and choose Character, once for each suspect. In the line under the name ("One line: who or what this is") write their motive, means and opportunity. Put the secret they are hiding in the entry's Backstory.
2. To mark the suspects, open the Role menu, choose Edit roles… and add a role called "Suspect", with a colour. The suspects then stand out in the Codex's list of characters.
3. Open the Outliner on the Draft and add a card for each scene with Add › Scene. In each synopsis, write what the scene does for the case: "Clue: Edwin's watch stopped at 11.40."
4. Open a scene and make three labels, "Clue", "Red herring" and "Reveal", each in its own colour. The pencil beside Status in the Inspector's Properties opens Edit labels & statuses.
5. Click Grid View to switch the Outliner to List View, and set each scene's label from its row. Read down the colours: every clue should sit above the reveal, spread through the book rather than bunched at the end.
6. Click Filters and pick "Clue" in All labels. Only the clue scenes stay on the list. Read them on their own: together, they should point at one person.
7. For the truth beside each scene, add a column with the + at the end of the list's header row (Add custom column) and call it "What really happened".

The same Codex can hold the setting, the timeline of the crime and the minor cast, as what to include in a story bible sets out. When a clue needs to move earlier, the Outliner is where you drag its card into place.

Common Mistakes

• Starting to draft before you know the answer. A mystery written forwards tends to end with a solution that the clues do not support.
• A culprit from outside the circle. If the reader never had a chance to suspect them, the ending feels like a cheat.
• Clues that are too loud. If the narration lingers on the stopped watch, the reader solves it in chapter three. Chandler's "false emphasis" works both ways.
• Red herrings with no explanation. Every false lead needs an innocent reason by the end.
• A detective who does not detect. A confession, a coincidence or a lucky find is not a solution.
• A sagging middle. Each round of the investigation should change what the detective believes.
• An ending that drags on. Once the question is answered, the story is nearly over.

Which Mystery Advice Is Misattributed?

• Chandler did not write "ten commandments". The ten-point list that circulates online, ending "It must be honest with the reader", is a condensed version printed in Nicholas Parsons's The Book of Literary Lists. Chandler's own text is "Twelve Notes on the Mystery Story", in his notebooks, and honesty with the reader is his third note, not his tenth. A separate set, "Casual Notes on the Mystery Novel" (1949), was printed in Raymond Chandler Speaking (1962).
• "When in doubt, have a man come through a door with a gun in his hand" was not advice. In the introduction to The Simple Art of Murder (1950), Chandler was describing what the pulp magazines demanded, and his next sentence is "This could get to be pretty silly".
• Poe's Dupin stories never call Dupin a detective. The word does not appear in "The Murders in the Rue Morgue" (Graham's Magazine, April 1841), "The Mystery of Marie Rogêt" or "The Purloined Letter". Merriam-Webster dates the first known use of "detective" as a noun to 1842. Poe called the stories "tales of ratiocination", and he thought people found them "more ingenious than they are".

Sources

Retrieved 30 October 2026.

• P. D. James, Talking About Detective Fiction (2009), read through Open Library's search inside (archive.org).
• Edgar Allan Poe to Philip P. Cooke, 9 August 1846, The Edgar Allan Poe Society of Baltimore; publication details of "The Murders in the Rue Morgue" on the same site; the Dupin stories in The Works of Edgar Allan Poe, volumes 1 and 2, Project Gutenberg eBooks 2147 and 2148.
• S. S. Van Dine, "Twenty Rules for Writing Detective Stories", The American Magazine, September 1928, reprinted in Howard Haycraft (ed.), The Art of the Mystery Story (1946) (archive.org) and in The Winter Murder Case (archive.org); full text at the Gaslight archive.
• Ronald A. Knox, introduction to The Best Detective Stories of the Year 1928 (Faber and Gwyer, 1929), reprinted in Knox, Literary Distractions (Sheed and Ward, 1958) (archive.org).
• Raymond Chandler, "Twelve Notes on the Mystery Story", in Frank MacShane (ed.), The Notebooks of Raymond Chandler (Ecco, 1976) (archive.org), and in Later Novels and Other Writings (Library of America, 1995); "Casual Notes on the Mystery Novel" (1949), in Raymond Chandler Speaking (1962) (archive.org).
• Raymond Chandler, "The Simple Art of Murder", in The Simple Art of Murder (1950), Faded Page; the 1950 introduction as reprinted in Trouble Is My Business (archive.org).
• Quote Investigator, "When in Doubt Have a Man Come Through a Door with a Gun in His Hand", 2014.
• Orson Scott Card, How to Write Science Fiction and Fantasy (Writer's Digest Books, 1990), on the idea story (archive.org).
• Nicholas Parsons, The Book of Literary Lists, for the condensed Chandler list (archive.org).
• Agatha Christie Limited, "The Detection Club", for the year it was formed and its members.
• Merriam-Webster, detective, first known use.
• Mystery Writers of America, Lilian Jackson Braun Award, eligibility rules.