In August 1816, crop failure, relentless rain and post-war unemployment leave London close to unrest. Lord Preston Farnsworth is found hanging upside down in a ruined chapel, posed like the Hanged Man tarot card, and an orphan who led Sebastian to the body vanishes.
The dead nobleman was celebrated as a campaigner against vice, but Sebastian discovers that his reforms injured and intimidated many of the people he claimed to save. When further victims are killed and marked with tarot cards, the murders threaten to ignite a city already divided by hunger, fear and demands for political change.