When Detective Mark Turpin is assigned the task of investigating the death of a local businessman, the case is first thought to be one of accidental drowning. Until a bullet hole is found where the victim fell into the River Thames. Then a number of graves are unearthed at a disused airfield site being redeveloped by the dead man, exposing a horrific secret and plunging Mark into one of the darkest investigations of his career. After two more bodies are discovered amongst the burnt-out ruins of a building on a nearby industrial estate, Mark realises that a serial killer is at large.