D.I. Duncan McAdam is dispatched home to the Misty Isle. A body has been found buried in a remote location on the Waternish peninsula. Well-preserved in the peat, Isla Matheson—missing for the better part of two decades—is revealed to a shocked island community. A teenage runaway is dead...and no one is talking.

When the chief suspect in the notorious "peekaboo cop killer" case blew himself up, almost taking lead investigator DCI Duncan Bone with him, the psychologically damaged detective thought his days on the force were over. But, when another PC is abducted and murdered in the same deranged peekaboo fashion, Bone is persuaded to return to lead the new investigation.

After an elite criminal profiling unit is shut down amid a storm of scandal and mismanagement, only one person emerges unscathed. Forensic psychiatrist Doctor Alexander Gregory has a reputation for being able to step inside the darkest minds to uncover whatever secrets lie hidden there, and soon enough he finds himself drawn into the murky world of murder investigation. In the beautiful hills of County Mayo, Ireland, a killer is on the loose. Panic has a stranglehold on its rural community, and the Garda are running out of time.

In the shadow of the Pentland Hills, a man has been callously struck down in front of his home. Tyre marks suggest it was no accidental hit-and-run. Somebody wanted him dead and as the man fights for every breath, they might still get their wish. Grappling with the demons he thought he could leave behind after months away on enforced leave, D.S. Malkie McCulloch resists pressure from his superiors to pass the case on to the road policing unit, convinced that whoever was behind the wheel will be waiting for the chance to finish the job.

A woman is found in a local cemetery, crushed to death under a gravestone. A production company is there, filming the remake of a classic sci-fi TV show on the grounds, making the investigation more difficult for DCI Harry McNeil. It's his first day in charge of the cold case unit in Edinburgh. After spending four years in Professional Standards, he has little choice but to take the promotion.