In late 1145, England remains divided between King Stephen and Empress Matilda, and an attempted peace meeting at Coventry fails to end the conflict. Brother Cadfael learns that Olivier de Bretagne, the son whose existence he has kept secret, disappeared after the surrender of Faringdon Castle and may be held by men whose loyalties have shifted during the war.
Cadfael leaves Shrewsbury without formal permission and enters the contested country around Gloucester and the Thames Valley. His search draws him into a murder accusation, a castle siege and the bitter division between Robert of Gloucester and his son Philip. The final chronicle brings Cadfael's monastic vocation into direct conflict with his duty as a father.