When Detective Clayton Tyler is tasked with reviewing the formidable archives of unsolved homicides in his police department's vaults, he settles on one particular cold case from the 1980s: The Chester Creek Murders. Three young women were brutally murdered—their bodies dumped in Chester Creek, Delaware County—by a serial killer who has confounded a slew of detectives and evaded capture for over thirty-eight years. With no new leads or information at his disposal, the detective contacts Venator for help, a company that uses cutting-edge investigative genetic genealogy to profile perpetrators solely from DNA evidence. Taking on the case, Madison Scott-Barnhart and her small team at Venator must use their forensic genealogical expertise to attempt finally to bring the serial killer to justice. Madison, meanwhile, has to weigh professional and personal issues carefully, including the looming five-year anniversary of her husband's disappearance.