December, 1145. Hamelin Isenmongere, trader in iron and charcoal from Gloucester, is considered by many to be the most popular man in Worcester. Why then is he found on the quayside near his warehouse with his head beaten in? As the winter bites, Undersheriff Hugh Bradecote, Serjeant Catchpoll and Walkelin begin the hunt for a killer.

However, matters are complicated when evidence leads them to Worcester Ccastle itself and the hunt for a spy in the midst of complicated political crosscurrents. Bradecote, Catchpoll and Walkelin must uncover whether the murder was an act of betrayal from close to home, or one that casts a shadow over the fight for England's crown.