During the severe winter of 1814, musician Jane Ambrose is found murdered in a snowdrift. Her employment in the household of Princess Charlotte alarms the palace, which tries to prevent questions about the heir presumptive and the rival factions seeking to control her future.
Sebastian and Hero follow Jane's contacts through musical, diplomatic and royal circles while crowds gather on the frozen Thames for a Frost Fair. The victim's private work and knowledge of the court expose a network of coercion in which an apparently powerless woman had become dangerous to influential people.