September 1940. With London having endured the Blitz for nearly a month people are calling for vengeance but once again the night heralds more destruction. In Custom House anxious residents dutifully head to the nearest public air-raid shelter as the warning siren wails. When dawn brings the all-clear people disperse but one man remains - he is dead stabbed through the heart. Detective Inspector John Jago discovers that the victim was a pacifist. But why then was he carrying a loaded revolver in his pocket?