The most violent thunderstorm in living memory occurs above a sleepy village on the West Coast of Scotland. A young couple take shelter in the woods, never to be seen again…DCI Jack Russell is brought in to investigate. Nearing retirement, he agrees to undertake one last case, which he believes can be solved as a matter of routine. But what Jack discovers in the forest leads him to the conclusion that he is following in the footsteps of a psychopath who is just getting started.