I was reading a P.D. James novel and realized I hadn’t added this most basic plot of all.  It honestly feels more like a technique than a plot.

  1. A crime happens.
  2. The solver either mentally or literally lists the suspects, their motives, their methods, and their opportunities to commit the crime, as if on one of those teeny checklists from the Clue game.
  3. When only one possible suspect remains, the crime is solved!
  4. The solver laboriously explains their methods in case the reader missed a clue.

A lot of mysteries tap into this, but don’t rely solely on it.  A note: some of the better mystery-writers will add a technique of corroboration.  If multiple people don’t confirm an alibi, then it can almost be assumed to be a lie.