I’ve come, over the past week or so, to realise that the best murder mysteries are, ultimately, about serial killers.
Not, necessarily, the Gory Hannibal Lecter type of serial killers; even the classic Agatha Christies, for example, seem to work even better when the Nemesis has a couple of (or preferably three) victims.
The classic Murder mystery pits a sleuth against a murderer. There’s a first murder – a hook; something to attract the attention of both the sleuth and the reader. Normality has been upset; the natural order has been broken, and must be restored.
And if there’s one murder, and the detective can investigate and, eventually, unmask the killer, then it can be a good story. But what makes it a Great story is when the stakes are upped.