Whodunit

A whodunit, a colloquial elision of the question Who has done it, is a complex, plot-driven variety of detective fiction in which the puzzle of who committed the crime is the main focus. The crime is treated as "a puzzle to be solved through a chain of inquiries", and the genre's signature structure is the double narrative: the hidden story of the crime is reconstructed alongside the open story of the investigation, so the reader can deduce the culprit before the reveal. The theorist Tzvetan Todorov treated that structure as a paradigm for fiction generally, a story unfolding toward a past event rather than a future one.

The word was coined by the reviewer Donald Gordon in 1930, per Merriam-Webster as the article relays, and the form flourished in the Golden Age of Detective Fiction between the world wars, when it was the predominant mode of crime writing and was dominated by British and female authors: Agatha Christie, Dorothy L. Sayers, Margery Allingham, Ngaio Marsh, with John Dickson Carr and Ellery Queen among the Americans who imitated the British style. Its conventions hardened into furniture: the secluded country house, the familiar cast, the misdirection toward an unlikely suspect. The inverted howcatchem flips the structure by revealing the culprit first; the whydunit makes motive the mystery. For web-serial writers the whodunit is the fairest puzzle contract in fiction, formalized in the fair-play mystery tradition, and the locked-room mystery is its showcase form. See how to write mystery.