When the corpse of an old man is discovered in a sack at the Abbey, Cadfael believes the man has been murdered. Among the suspects are a group of pilgrims, including two thieves. Cadfael imprisons them in a bid to draw out the killer.

When a potter gives up his former life to enter the monastery just as his wife dies, the other monks all suspect him of murder. But as Cadfael begins to investigate, he uncovers a bizarre web of jealousy, infidelity and suicide pacts.

Prior Herluin and his apprentice, Tutilo, arrive from a distant abbey that has been sacked in the civil war, requesting the loan of the bones of St Winifred. Abbot Radulfus finds it hard to refuse him, but then a local benefactor comes to his rescue, and he decides to keep the holy casket. Then a beautiful slave girl, Daalny, and the bones of St Winifred are abducted from the Abbey, and Cadfael is commissioned by the abbot to find them both. But a man is found murdered before Cadfael can determine what has been happening.