Mystery writing prompts: 99 mystery story ideas by subgenre

A good mystery writing prompt hands you a question with a findable answer, such as a body, a theft or an impossibility, and someone with a reason to look for it. The 99 mystery story ideas below are original and grouped by subgenre: cozy, amateur sleuth, police procedural, locked room, noir and historical, with clue prompts and first lines at the end. Pick one, decide who did it and why before you write a word, then open on the moment somebody finds the problem.

Each subgenre promises the reader something different, so choose a row in the table by the promise you want to keep. The story ideas page has fourteen more crime premises, none repeated here. This page is for finding the premise. For the whole road from premise to finished book, with the crime card, fair clues and the reveal, see how to write a mystery novel.

Cozy mystery prompts

A cozy needs a community small enough that everyone is a suspect, an amateur with a reason to be in every kitchen, and violence kept offstage. The puzzle can be dark while the tone stays warm.

1. The judge of a village jam competition is found dead in the church hall, face down among the strawberry entries. Every jar on the table has been opened except one.
2. A knitting circle in Bar Harbor notices that the scarf one member has worked on all winter has a strange pattern of dropped stitches. Laid out flat, they match the dates of four burglaries on the harbor road.
3. A secondhand bookseller in Hay-on-Wye finds a first edition on her shelf that she never bought, with a library card inside belonging to a man who drowned last spring.
4. The hundred-year-old sourdough starter at Dunmore's Bakery is stolen the night before the county fair. The only other jar of it was left, in writing, to the baker's estranged son.
5. The vicar's wife runs the village lost-and-found and notices that the same green umbrella has been handed in three times this month, by three different people, each of whom found it somewhere they shouldn't have been.
6. During a storm that cuts the power at a Cornish guesthouse, a guest is found dead in the library. Everyone says they were in the parlor singing hymns by candlelight, and the landlady, a retired choir director, heard one voice missing from the alto line.
7. A caller to a small-town radio gardening show asks, very casually, how deep to plant a rosebush over something large. The host recognizes the voice as the mayor's.
8. The organist of St. Wendel's dies at the keyboard during evensong. The hymn numbers he posted on the board that morning don't match any service, and the churchwarden's granddaughter thinks they're page numbers.
9. A dog groomer in Asheville finds a diamond earring tangled in a poodle's coat. The owner swears she has never owned a diamond, and the earring matches a pair missing from a widow's house two streets away.
10. The village postmistress notices that old Mr. Penhale hasn't collected his pension in a month, but his weekly letters to his sister in Australia keep arriving at the counter, in his handwriting.
11. In the week of the scarecrow festival, one of the scarecrows on the high street is wearing the clothes the missing parish treasurer was last seen in.
12. A book club's chosen novel, by an unknown author, describes an unsolved death in their village in details only a local would know. One of the six members wrote it.
13. A florist in Savannah is paid in cash every year to deliver the same funeral wreath to the same grave. The card is always signed by the man in the grave.
14. At a Tuscan cooking school, the instructor's famous ragù recipe disappears from her locked drawer. The thief must be one of the eight students, and all eight are lying about something else.

Amateur sleuth prompts

An amateur needs what the police lack: access, and a particular kind of knowledge. G. K. Chesterton's Father Brown, a priest whose first book of cases was The Innocence of Father Brown (1911), explains his in “The Blue Cross”: “Has it never struck you that a man who does next to nothing but hear men's real sins is not likely to be wholly unaware of human evil?” Each sleuth below has a job that taught them something.

15. A piano tuner who visits forty homes a month notices that a widow's piano has been tuned by someone else, badly, the week her husband died.
16. A court stenographer rereads the official transcript of a murder trial she typed eleven years ago and finds one word changed on page 212. It's the word that convicted the man.
17. A sommelier at a charity dinner tastes a rare Bordeaux and knows it's younger than its label. A week later, the man who donated it is found dead in his own cellar.
18. A hospice nurse notices that three patients changed their wills in the week before they died, each leaving money to the same small charity.
19. A tattoo artist recognizes her own work on a body pulled from the river: a design she drew for only one client, who is alive and booked into her chair on Thursday.
20. A ghost-tour guide in Edinburgh tells the same story every night about a woman who vanished in 1974. One night a man in the group quietly corrects the color of her coat.
21. A retired weather forecaster reading about a murder trial notices that the key witness describes a thunderstorm on a night she knows was clear across the county.
22. A sound engineer is asked to clean up a missing girl's last voicemail for the police. Under the traffic noise she hears a station announcement from a rail line that closed in 2019.
23. A school librarian notices that a quiet student borrowed every book in the library on poisons, in order, and returned them all on the morning his stepfather was taken to hospital.
24. A carpet fitter replacing the stair runner after an old man's fatal fall notices that the scuffs on the wallpaper go up the stairs, not down.
25. A stage manager notices that on the night the leading man collapsed onstage, his understudy was already in costume and makeup at the half-hour call.
26. A hairdresser in a Glasgow salon hears three clients tell three versions of the same Saturday night, and only one of them mentions the fire.
27. A conservator cleaning the skeletons in a natural history museum's long gallery notices that one of them has gained a bone, and the new one is human.

Police procedural prompts

In a procedural the investigation is the plot: the order things must be done in, the rules of evidence, the team, and what happens when someone skips a step.

28. A detective three weeks from retirement is handed a cold case: her own first case, which she closed with a confession she's no longer sure was true.
29. A body is found on a bridge exactly on the county line, and two sheriff's departments that have loathed each other for a generation both claim it, then both try to give it away.
30. An evidence-room clerk notices that a bag of evidence from a 1994 murder was signed out last month by a detective who died in 2001.
31. A lab technician finds the same DNA profile at three unconnected crime scenes. It belongs to a constable who attended all three, and who swears he touched nothing.
32. A missing-persons detective gets a call from the woman she has been searching for, who says she is safe and asks her to stop looking. Then she names the person who reported her missing.
33. A sergeant is found dead in the station locker room during a shift change, and every suspect is a police officer with a reason to want the case given to a friend.
34. A passenger is found dead in her cabin on the overnight ferry from Harwich to the Hook of Holland. British and Dutch detectives argue over jurisdiction, which depends on what time she died.
35. A cold-case unit gets a familial DNA match on a 1987 murder. The match is the lead detective's own niece, who sent off a test for fun.
36. A forensic sketch artist draws a suspect from a witness's description and finishes with her own son's face looking back at her.
37. A man walks into a station and confesses to a murder. There is no body and no missing-person report, and he insists the detectives check the address before the end of their shift.
38. A run of burglaries in a quiet suburb has the squad baffled, because nothing is ever stolen. In every house, one family photograph has been turned to face the wall.
39. A collision investigator measuring skid marks on a mountain road realizes the car sped up into the bend. The driver's widow has already had the car crushed.
40. Internal affairs is asked to investigate the detective with the best clearance rate in the city. Every one of his solved cases has the same eyewitness.
41. A probationary officer's body-camera footage of a routine traffic stop is missing four seconds. Her training officer tells her the cameras glitch all the time.

Locked-room and impossible crime prompts

Edgar Allan Poe's “The Murders in the Rue Morgue” (Graham's Magazine, April 1841), one of the first detective stories, is also a locked-room puzzle: “The door leading from the front room into the passage was locked, with the key on the inside.” The pleasure is the impossibility. The fairness is that the reader could have solved it.

42. A passenger vanishes from the dome car of a sleeper train halfway through a twelve-mile tunnel. Seven people watched her walk in, and both doors were in view the whole time.
43. A chess player collapses inside a sealed, soundproof booth during a televised tournament game. Four cameras were on him throughout, and nobody else came near the glass.
44. A ski instructor is found dead in the middle of a freshly groomed slope, with only her own ski tracks leading to her.
45. A bank manager is found dead inside a vault on a time lock that hasn't opened since Friday. The logs say the door never moved, and the bank wants the case closed by Monday.
46. Twelve people are holding hands around a séance table when the lights come back on and the medium is dead. Every one of them swears no one let go.
47. A researcher is found dead in a sealed Antarctic station in midwinter, when no plane can land until spring. The other eleven residents were all on camera in the mess hall at the time.
48. Eight people eat soup from the same tureen at a family dinner, served with the same ladle. Only the grandfather dies, and only his bowl tests positive.
49. A small painting disappears from a museum wall during a guard's shift, though she sat facing it the whole time. She's sure she never looked away, and the frame is still hanging.
50. A man is found shot in a study bolted from the inside, and there is no gun in the room. The only thing missing is the goldfish.
51. A hiker is found drowned in a dry canyon in Utah, miles from any water, with sand in her boots and fresh water in her lungs.
52. A hotel guest is found dead in a room with the chain on and the door bolted, fourteen floors up. The room-service tray outside the door has two cups.
53. A magician is found dead in the sealed water tank at the end of his escape act, in front of nine hundred people. His assistant's stopwatch says he died before he went in.
54. A woman is on camera in a Lisbon café at the moment her husband is killed in their apartment in Porto, three hours away by car. She has no twin, and the café's clock is right.
55. The building's only elevator stalls between the ninth and tenth floors for twelve minutes. When it moves again, its one passenger is dead, and the camera inside shows nobody else.

Noir and hard-boiled prompts

Hard-boiled fiction, in the line of Dashiell Hammett and Raymond Chandler, follows a tough investigator through a crooked city. Noir runs darker still: its hero is as likely to be the one in trouble as the one asking questions, and the solution rarely fixes anything.

56. A disgraced insurance investigator in Reno is hired by a widow to prove her husband's death was an accident, so she can collect. The more she proves it, the less she believes it.
57. A private investigator who takes jobs through a gig app gets a one-star review from a client who was found dead the day before it was posted.
58. A lounge singer at a Miami club is asked by a detective to inform on her boss, and the same night her boss asks her to inform on the detective. Both pay in cash, and both know about her brother.
59. A tow-truck driver in El Paso hauls a car from a no-parking zone and finds a wedding dress on the back seat and a bullet hole in the windshield. Nobody ever comes to collect it.
60. A detective who has taken envelopes from the same bookmaker for fifteen years is assigned the bookmaker's murder. Everyone in the squad room is watching to see how hard he looks.
61. A woman walks into a private investigator's office in Marseille and hires her to prove she's alive. The state declared her dead six months ago, and someone in Lyon has been living as her ever since.
62. A political fixer in New Orleans is paid to make a scandal disappear by Monday. The scandal is a dead woman in a French Quarter apartment, and he recognizes her from his own past.
63. A crime reporter who was fired last spring still listens to the police scanner every night. Tonight he hears his own address called in.
64. A casino's oldest card dealer is asked by the new owners to name the regulars who cheat. She has been helping one of them for twenty years.
65. A charming man hires an investigator to find his missing wife. She finds her easily, alive and hiding from him, and the wife offers double to tell him she's dead.
66. A retired boxer working the door at a jazz club is paid to throw a man out at midnight. The man is found dead in the alley at ten past, and everyone saw the boxer's hands on him.
67. A private eye who lost his license works out of a laundromat. His only client is the cop who took it from him.

Historical mystery prompts

The period decides what your detective can know. List the tools your sleuth doesn't have yet, then turn each missing one into a scene.

68. In Rome, on the night of the great fire of 64, a freedwoman who runs a bakery is accused of starting it in her own ovens. She has three days to find out who did.
69. During London's Great Stink of 1858, a sewer engineer finds a body in a new tunnel that has no entrance yet.
70. In Edo in the 1700s, a fire-watch lookout sees a lantern signal from a tower that should be empty, on the night a rice merchant is killed.
71. In 1925 Harlem, a numbers runner who remembers every bet notices that a dead man's numbers are still being played, in his exact pattern, every day.
72. In a Flemish cloth town in 1380, a dyer is found drowned in a vat of blue, and each of the town's guilds insists the investigation belongs to them.
73. In 1880s Manchester, a young telegraph clerk notices that the same coded message was sent to a dozen men, each on the day before he died.
74. During the Blitz, an air-raid warden digging through a bombed house finds a man who was dead before the bomb fell, in a house that was supposed to be empty.
75. In a village of tomb builders in ancient Egypt, a painter is accused of robbing the tomb he decorated. He knows who did it from the way the thief cut the plaster.
76. At a summer ball in Saratoga Springs in 1885, a young widow finds a name she didn't write on her dance card, beside the last waltz. The man was buried that morning.
77. In 1849 San Francisco, the harbor is crowded with ships abandoned by crews gone to the gold fields. A harbor pilot boards one and finds its crew still aboard, dead at the table.
78. During the New York blackout of 1977, a jeweler's shop is emptied, and the jeweler insists the thief had a key and never needed the dark.
79. In Vienna in 1900, a psychiatrist's patient keeps describing a murder in her dreams, in a building nobody has heard of. Then a detective finds the building.

Clue and red herring prompts

Each prompt here starts from a single clue or a red herring. Decide what it really means, what the reader will think it means, and who put it there. Where to plant it and how it pays off belong to the outline, and the guide to writing a mystery novel covers both.

80. A victim's broken watch shows 9:14, and everyone in the house can account for 9:14. The question is who knew the watch ran eleven minutes fast.
81. A cup of tea is still warm on the table beside a woman who has been dead for hours.
82. The victim's glasses are folded neatly on the nightstand, but she couldn't see a step without them, and she died at the bottom of the stairs.
83. A shopping list in the victim's handwriting includes the one food he was allergic to.
84. The victim's phone shows forty-three unread messages and one that was opened after she died. It came from her own number.
85. The victim's dog was fed, walked and given fresh water the morning after the murder.
86. The obvious suspect lies about where she was that night. Write the scene where the detective learns what the lie was really hiding, something smaller and sadder than murder.
87. The study window was open all night in freezing rain, and the carpet beneath it is dry.
88. A restaurant receipt for two steak dinners, dated the night of the murder, turns up in the pocket of a man who says he ate alone.
89. A threatening letter was typed on the victim's typewriter, whose r always drops below the line. In the letter, every r sits level.

Mystery first lines

Use one as your first sentence and write the next without stopping. Each hides a question the rest of the story has to answer.

90. “The body was found in the one room of Aldwick House that nobody had ever been allowed to clean.”
91. “My aunt solved her first murder at eighty-one, mostly to prove the vicar wrong.”
92. “Everyone at the reading of the will had a motive, which the lawyer seemed to find funny.”
93. “The fourth time someone confessed to killing Gerald Marsh, I started to wonder whether anyone had.”
94. “It rained for nine days in Port Aster, and on the tenth they found the second car.”
95. “I knew she was lying because she described the weather, and nobody describes the weather.”
96. “Dad always said the town had only one secret, and that everybody knew it.”
97. “The night clerk said the woman in room 6 had checked in alone, which was odd, because two people checked out.”
98. “By the time I reached the lighthouse, the keeper's log had one page torn out, and it was the page I had come to read.”
99. “Nobody in the village had locked a door in forty years, which made the key in the dead man's hand all the more interesting.”

Turn a prompt into a case

A prompt gives you the first scene and a question. These steps turn it into a case you can plot, before you start the full outline.

1. Name the question

   Decide exactly what is unknown: who did it, how it was done, why, or whether it was a crime at all. The drowned hiker in prompt 51 is a how. The changed transcript in prompt 16 is a who and a why. The question decides what your sleuth spends the book looking for.

2. Close the circle

   List everyone the setting allows. The guesthouse in prompt 6 gives you the guests, the landlady and whoever came in from the storm. Four to six names, each with a reason to be there, is enough to start. If anyone in the city could have done it, add a storm, a guest list or a locked gate.

3. Give the sleuth a stake

   Why can this person ask questions, and why won't they stop when someone tells them to? The stenographer in prompt 16 typed the word that convicted a man. Nobody can take that stake away from her.

4. Decide the answer before page two

   Pick the culprit from the circle and write the motive in one sentence. Then fill in the crime card from the guide to writing a mystery novel, and list the chapters in a novel outline once the case holds.

5. Use the clue the setting hands you

   Most prompts have a clue built into the place: singing in the dark, one set of tracks in fresh snow, a name on a dance card. Before you invent a clue, use the one the setting already offers. A clue that grows out of the place tends to feel inevitable rather than planted.

6. Write the discovery in the subgenre's voice

   The first scene tells the reader which promise you're making. Write the moment the problem is found, which is usually your inciting incident, in the voice of your subgenre. Plant one clue in it, and end the scene when the sleuth decides to look.

   To check that the scene doesn't give the game away, select it and ask the Strokes Assistant who a first-time reader would suspect after it, and why. If the answer is your culprit, the scene says too much. Treat the answer as one reader's guess.

Here is prompt 85, the dog that was cared for after the murder, as the opening of a cozy and then of a noir. The clue is the same in both.

The facts match: someone who knew the house cared for the dog after the death. What changes is the promise. Mrs. Tilley notices the bowl the way a neighbor would, as a thing out of place in a tidy life, so the cozy promises a puzzle the reader can play along with and a village that will be set right by the end. The private eye notices the kibble through his own fee and his own loneliness, so the noir promises an answer that will cost him something and may not fix anything. The subgenre lives in what the narrator sees first.

Mistakes that spoil a mystery prompt

A promising prompt often goes wrong in the first chapter, before the clues even start. Watch for these.

• Starting with the backstory. Two chapters on the village and the victim's marriage before anyone dies. Open on the discovery and let the history come out as testimony.
• A circle with no edge. If anyone in the city could have done it, the reader can't play along. Close it with a place, a guest list, a storm or a deadline.
• Expertise the reader can't share. When the piano tuner hears a wrong note, the reader has to hear it too. Show what your amateur knows in an ordinary scene early on, so the clue lands as a discovery and not a lecture.
• Breaking the subgenre's promise. Graphic violence in a cozy or a joke-a-page noir can send readers back to the shop. Mixing is fine. Breaking the contract by accident isn't.
• All twist, no puzzle. A prompt can hand you a great last-page surprise and no questions to ask along the way. Build the investigation first, then see whether the twist still fits. The plot twist ideas show how to set one up fairly.
• A thriller in disguise. If the story's question is whether the hero can stop something rather than who did something, you may be writing a thriller, which runs on different rules. The guide to how to write a thriller covers them.