Every 73-75 years a comet travels close to Earth, opening a rift between dimensions that allows paranormal entities to travel through. These entities are called preternaturals and unfortunately most are criminals. As a result, human police forces work with preternatural Councils all over the world to handle matters of crime. Half-human, half-demon, Nix De La Fuente is a special liaison reporting to the Phoenix, Arizona Council. When her vampire friend is murdered - the second vampire death in days - Nix is determined to find the killer. She is shocked to learn her former lover Tobias Caine - the vampire who'd walked out on her five years before - has been assigned to investigate with her. Rumours begin stirring that a demon may be responsible for the murders and Nix herself becomes a suspect but as more bodies turn up, the evidence points to Tobias's arch enemy, Natchook, whom Tobias felt was responsible for the assassination of his vampire leader centuries before. The only problem is Tobias has no idea where Natchook may be hiding.
With the Council determined to get rid of Nix and murders steadily on the rise, time is running out, forcing Tobias and Nix to put aside their past in hopes of saving their futures.