Whodunit
Also known as whodunnit
A mystery built around one question, who committed the crime, in which the audience gets the same clues as the detective and the culprit is revealed at the end.
In practice
A whodunit is a mystery story organized around a single question: who committed the crime? A murder or theft happens early, a detective investigates a closed circle of suspects, and the answer is withheld until the end, when the detective explains how the clues point to one person.
The word, a contraction of who done it, appeared in American publishing in 1930, during the golden age of detective fiction. Agatha Christie, Dorothy L. Sayers and Ellery Queen wrote the classic examples, and Christie's Murder on the Orient Express (1934) remains the best known.
Its central promise is fair play: the reader or viewer gets every clue the detective gets and could solve the case first. Writers of the period even published rules, such as Ronald Knox's ten commandments of detective fiction (1929). On screen, the form has returned with Knives Out (2019) and its sequels.
A whodunit scene in screenplay form
INT. LIBRARY - THORNE HOUSE - NIGHT
All six suspects, arranged on sofas like a family portrait. DETECTIVE ADA OKAFOR stands by the dead man's chess board.
ADA
He was killed at a quarter past ten. Five of you have someone who saw you at that hour.
She moves one chess piece.
ADA (CONT'D)
The sixth has a witness too. But the witness is a clock, and the clock was wrong.
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The gathering of the suspects is the whodunit's classic finale. Every clue Ada uses must already have appeared on screen, here the clock and the chess board, so the audience can feel that they might have solved it themselves.
How a whodunit works
The classic structure has four parts: the crime, the investigation, a turn where the obvious suspect is cleared or a second crime happens, and the reveal. The suspects form a closed circle, such as the guests at a house, the passengers on a train or the members of a family, so the culprit must be one of them.
Clues and red herrings are the genre's machinery. A clue points toward the truth, a red herring toward a false answer, and the best clues are hidden in plain sight among details the audience notices for another reason.
Whodunit movies and series
Murder on the Orient Express (1974): Sidney Lumet's adaptation of Christie traps Hercule Poirot on a snowbound train with a dozen suspects.
Clue (1985): six guests, one mansion and several possible endings. The comedy plays with every convention of the form.
Gosford Park (2001): a murder at a 1930s shooting party, seen as much from the servants' quarters as from upstairs.
Knives Out (2019): a famous crime novelist dies after his birthday party, and a detective questions his greedy family.
Only Murders in the Building (2021): three neighbors who love a true crime podcast investigate a death in their apartment block, one season per case.
Whodunit vs. howcatchem
In a whodunit, the audience does not know who the killer is until the end. In an inverted mystery, sometimes called a howcatchem, the audience sees the crime and the killer at the start, and the pleasure is watching the detective work it out.
Columbo is the classic howcatchem, and Poker Face (2023) revived the form. The choice changes the suspense: a whodunit asks who, while a howcatchem asks how the detective will catch someone the audience already knows.
How to write a whodunit
Write the solution first. Decide who did it, how and why, then work backward to the clues the culprit leaves and the false trails that point elsewhere.
Give every suspect a motive and a secret. A good secret makes an innocent suspect act guilty, which is the most natural red herring.
Show each clue on screen before the reveal, ideally while the audience is looking at something else. A clue mentioned only in the final explanation breaks fair play.
Track the evidence. In Plot, a note on each scene can record which clues it plants, so you can check before the reveal that every one was shown.
Common questions
What is a whodunit?
A whodunit is a mystery in which the main question is who committed the crime. The audience follows the investigation and the culprit is revealed at the end.
Where does the word whodunit come from?
It is a contraction of who done it, first recorded in American publishing in 1930, during the golden age of detective fiction.
Is it whodunit or whodunnit?
Both spellings are correct. Whodunit is the usual American spelling, and whodunnit is more common in British English.
What makes a good whodunit?
Fair play, a closed circle of suspects with real motives, clues shown in plain sight and a solution that surprises but feels inevitable once explained.
What is a reverse whodunit?
A reverse whodunit, or howcatchem, shows the crime and the culprit first, and the suspense comes from how the detective proves it, as in Columbo.