On New Year's Eve, partygoers at a secluded nature reserve north of Glommen discover a man's body rising from an old stone quarry.

The victim is a quiet accountant from Varberg with no known enemies — only an obsessive passion for genealogy and secrets he was determined to protect.

As threatening notes appear and firebombs explode, Detective Chief Inspector Kajsa Rudolfsson uncovers a web of extortion and a criminal network with roots stretching far beyond Swedish borders. But there's someone that will stop at nothing to keep the past buried.

With her marriage fraying under pressure and her closest colleague facing a family reckoning, can Kajsa catch the killer before they strike closer to home?

Unknown Origins is the fourth installment in the atmospheric Falkenberg Murders series.