Cadfael's novice, Brother Oswin, is found close to death, babbling about a woman. When a nun is found raped, murdered and encased in the ice of a frozen stream, Oswin is accused of murder. Cadfael tracks the nun's companion, Ermina Hugonin, and sets out to prove Oswin's innocence.

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.

The monks of Shrewsbury go to Wales to recover the bones of St. Winifred. But their attempted bribery of the Welsh puts them at odds with the local residents—and when the local landowner is found murdered, the monks are regarded as prime suspects.