When Laurie Montgomery temporarily steps down from her position as Chief Medical Examiner, she and Jack find themselves uncharacteristically free for a couple of weeks. And the timing couldn’t be better when they receive a call from Jack’s former medical school classmate, Robert Neilson, who is the sole family practitioner in Essex Falls, an idyllic town tucked away in New York State’s Adirondack Mountains. Serving also as the Hamilton County coroner, Dr. Neilson is in over his head trying to explain the sudden death of a young, healthy pest control worker on top of an outbreak of rapidly progressive Alzheimer’s-like cases, and he pleads with Jack and Laurie to come lend a professional hand. Unable to resist a good mystery and a vacation in one, Laurie and Jack agree to help and head upstate.

Essex Falls is beautiful enough and their accommodations are even better than they imagined. But they soon learn the town has suffered a major economic and social setback, which has shaken its residents to their cores. When the body of the pest control worker disappears without a trace just prior to an autopsy, Jack’s penchant for solving forensic conundrums launches him into a full-scale investigation that uncovers the most frightening modus operandi of his career so far.