Four bodies have been discovered along Europe’s riverbanks, placed with care—and completely drained of blood. Pinpricks on their throats indicate a slender murder weapon, but DNA found in the wounds suggests something far more sinister. Tasked with investigating, the FBI recruits Agents Della Hamilton and Mason Carter to Blackbird, an international offshoot of the Krewe of Hunters. If you want to catch a vampire killer, you need agents who can speak with the dead.

It's a pub in lower Manhattan, run by the Finnegan family for generations and now owned by Kieran and her three brothers. Kieran Finnegan, who still works there whenever she can, has become a criminal psychologist - a fitting reaction, perhaps, to her less-than-lawful past. Meanwhile, New York's Diamond District has been hit by a rash of thefts. No one's been killed - until now.

A ritualistic murder on the side of a remote road brings in the Florida state police. Special Agent Amy Larson has never seen worse, and there are indications that this killing could be just the beginning. The crime draws the attention of the FBI in the form of Special Agent Hunter Forrest, a man with insider knowledge of how violent cults operate, and a man who might never be able to escape his own past.

When FBI special agent Luke Kendrick discovers chilling evidence of dozens of victims at a crime scene in London, he recognizes the calling card of the notorious H. H. Holmes Society. Named for the eighteenth-century monster regarded as America’s first serial killer, the society is comprised of a twisted web of killers, working to carry out heinous murders in Holmes’s memory. And now the group’s been linked to a Scottish castle turned B and B—where guests check in but never check out.

When FDLE special agent Amy Larson discovers a small horse figurine amid the bloody aftermath of a gang massacre in the Everglades, she recognizes it immediately. The toy is the calling card of the apocalypse cult that Amy and her partner, FBI special agent Hunter Forrest, have been investigating, and it can only mean one thing: this wasn’t an isolated skirmish—it was the beginning of a war.