Truth be told, the private eye of Chandler and Hammett and their hard-boiled successors has more in common with the vampires and werewolves of horror fiction than with most real-life private investigations. Whereas their fictional counterparts are solving murders, unraveling plots, and walking through the bad neighborhoods that even the cops dare not enter, the real-life PIs spend their days documenting adultery for sleazy divorce lawyers, dealing with corporate security and industrial espionage, and investigating fraudulent insurance claims. The urban fantasists are only taking the trope one step further. Sam Spade has more in common with Harry Dresden than either of them do with the people you’ll find listed under “Private Investigators” in the yellow pages.

Raymond Chandler also wrote:

The private detective of fiction is a fantastic creation who acts and speaks like a real man. He can be completely realistic in every sense but one, that one sense being that in life as we know it such a man would not be a private detective.

The heroes of urban fantasy come out of the hard-boiled mystery, while the villains, monsters, and antagonists have their own roots in classic horror . . . but it is the combination that gives this subgenre its juice. For these are two genres that are at heart antagonistic. Horror fiction is a fiction steeped in darkness and fear, and set in a hostile Lovecraftian universe impossible for men to comprehend, a world where, as Poe suggested, death in the end holds dominion over all. But detective fiction, even the grim, gritty, hard-boiled variety, is all about rationality; the world may be dark, but the detective is a bringer of light, an agent of order, and, yes, justice.

You would think this twain could never meet. But bastards can break all the rules, and that’s half their charm. The chains of convention need not apply.