Catherine Grayston wants to save her marriage. A vacation in the quiet French village of Rousinac will surely help. Tom Grayston harbors a terrible secret that has pushed them apart. The town's secrets are far more frightening. When the couple doesn't return to England, Tom's work colleague and forensics specialist, David Frankel, sets off to France to find out what happened. He brings along eccentric and well-known criminal profiler James Harrison who can spot telltale patterns in criminal activity with savant-like brilliance and is sure to be invaluable to the case-as long as he keeps his promise to stay on his meds. What should be a routine investigation in Rousinac gets hampered at every turn by local residents who have a lot to hide. How far down the rabbit hole will David and James have to go to solve the mystery of the Grayston's holiday gone wrong? What does the frightening honeycomb of tunnels underneath the town have to do with the couple's disappearance? And why are the well-organized residents of Rousinac so hell-bent on covering up the truth at all costs?