June 1917. 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, and as the killer has taken care to remove identifying items, Detective Inspector Marmion and Sergeant Keedy struggle to name the victim before they can begin properly with their investigation. 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. The interminable presence of war and pitched battles between rival gangs suggest the Home Front is more insecure than ever before.