Mild-mannered amateur detective Albert Campion finds himself and his family caught up in a terrifying series of events. Meg Elginbrodde has believed herself to be a widow for five years. Yet since she announced her intention to remarry, she has been receiving some very odd communications: photographs of her husband, Martin, looking very much alive. But why? Is it blackmail, or something more sinister? Chief Inspector Luke joins forces with Campion to uncover the truth. And, amid the gloom of London's November smog, they begin to draw the net round a man who's 'killing mad'.