There’s two plots in a mystery novel: what actually happened, and how the detective figures it out. My understanding is that the short story he describes is th

There’s two plots in a mystery novel: what actually happened, and how the detective figures it out. My understanding is that the short story he describes is the former, and defines the puzzle part of the mystery: what clues are available, where are they, and what do they really mean? The actual novel, though, is the story of the investigation. It can be written in any way the author likes, so long as the detective only uncovers clues that the prewriting indicates should exist. One clear example of this distinction is the old Columbo TV series, where the murder happens onscreen at the beginning of each show. The bulk of the time is spent on the mental sparring match between the culprit and the detective.