1916: While German Gotha bombers raid London from above, a man's body is fished from the Thames below. The man had been garrotted and his tongue cut out before he was left to his watery grave, and as the killer had taken care to remove identifying items and even labels, Inspector Marmion and Sergeant Keedy struggle to name the victim before they can begin properly with their investigation. As family and business associates are found, the list of suspects grows ever longer; and as Marmion wrangles with the case, he and his family must also contend with their anxieties for his now-missing son, Paul. With great care, Marmion must pick his way along a twisting path that will lead him towards the killer.