Inverted detective story

An inverted detective story, also known as a "howcatchem", is a murder mystery fiction structure in which the commission of the crime is shown or described at the beginning, usually including the identity of the perpetrator. The story then describes the detective's attempt to solve the mystery. There may also be subsidiary puzzles, such as why the crime was committed, but those are cleared up along the way. This format is the opposite of the more typical "whodunit", where all of the details of the crime and the perpetrator are not revealed until the story's climax.