It's June 1814, and several royal families have gathered in London at the Prince Regent's invitation to celebrate the defeat of Napoléon, but the festive atmosphere is marred by the murder of a disgraced British nobleman long thought dead. Sebastian St. Cyr, Viscount Devlin, is drawn into the investigation—his 15th, after Who Slays the Wicked—by his valet, Jules Calhoun, an old friend of the dead man. Now Sebastian must discover: Why did Nicholas risk his life by returning to England? And who was the boy he brought with him?