When she's sent to a crime scene and finds her second dead woman in as many weeks, half-banshee detective Kiera "Mac" McLoughlin is convinced a serial killer is on the loose. Incubi are extinct, her boss insists. But what else can kill a woman in the throes of pleasure? When her partner is murdered after using witchcraft to locate the killer and Mac is thrown off the case, her frustration turns to desperation.

Certain the killer is an incubus, Mac works behind her department's back to chase down slim, sometimes perilous leads. While the killer eludes her, she does discover handsome Aidan Byrne, an investigative counterpart from the enigmatic Otherworlder Enforcement Agency. Mac typically runs her investigations fast and hard, but with Aidan at her side, she's running this one "hot" as well. But Aidan knows more than he's letting on-something that could shatter their blazing romance and add Mac to the killer's growing body count...