A marine engineer is found hanged in a locked apartment. Some artwork is stolen, then mysteriously returned. A security guard is found dead at the base of a Welsh cliff. When Fiona Griffiths is tasked to look through a stackload of cold cases, her bosses don't expect her to find anything of interest. But then she finds that an impossible robbery really happened. That a nailed-on suicide was anything but. That the dead security guard was almost certainly murdered. Before long, Fiona is embroiled in what will become the toughest case of her career so far--one that forces her to enter the heart of darkness, and a journey that will test her mental toughness to its very limits.