On a chilly morning in February, DCI Claire Pierce is called off her latest investigation—an animal sacrifice case—to a graveyard in Nottinghamshire, where a murder scene looks set to re-open an old case.

Three times before, Yorkshire's Ritual Crime Unit tried and failed to catch the "Valentine Vampire," a ritualistic serial killer whose victims show up drained of blood. Fourteen years after the last deaths, it seemed the case would never be solved.

Now there's another body, and if the killer's pattern holds up, there are at least two still to come. Last time, Pierce's superiors had insisted she hunt for a monster she knows doesn't exist, that can fly and turn to mist; the media had a field day, and the "Vampire" became the subject of a best-selling book. This time she's determined to find and stop the all-too-human culprit before it's too late.