A rich priest is found killed, and the finger of suspicion points to a new monk at Shrewsbury Abbey. Meanwhile, a civil war raging around England is piling political pressures on the Abbot. Cadfael investigates the murder and uncovers a tangled web of dishonesty and nepotism.

Cadfael puts Hugh Beringar to the test, and Hugh has to choose between loyalty to the king and friendship with Cadfael. Meanwhile, at the annual St. Peter's Fair in Shrewsbury, townspeople come into conflict with the Abbey's officers and with visiting merchants. A curfew is ordered, but not fully observed—then Cadfael finds he has a murder to solve.