whodunit
\hoo-DUHN-it\
noun
1. Informal. a narrative dealing with a murder or a series of murders and the detection of the criminal; detective story.
Quotes
The rival investigative teams have helped turn the case into a whodunit that has gripped the nation. They have failed to agree even on such basic facts as the time of death.
-- Taos Turner and Reed Johnson, "In Alberto Nisman Case, a Body, a Pistol and Few Answers in Argentina," Wall Street Journal, May 15, 2015
Origin
Whodunit entered English in the 1920s from the question "Who done it?", which stems from the standard English "Who did it?"
Dictionary.com
