whodunit

[ hoo-duhn-it ]
/ huˈdʌn ɪt /

noun Informal.

a narrative dealing with a murder or a series of murders and the detection of the criminal; detective story.
Also especially British, who·dun·nit.

Origin of whodunit

1925–30; jocular formation from question Who done it?, for standard English Who did it?
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for whodunit