From BBC Radio 4 Extra. Written by Ellis Peters; Full-cast dramatisation starring Philip Madoc as Brother Cadfael, with Michael Kitchen and Susannah York; Dramatised by Bert Coules.

It is 1141. In Shrewsbury, civil war is tearing the country apart as the bitter feud between King Stephen and Maud shows no sign of abating. Cadfael, safe within the peaceful walls of the Abbey, does not expect to be drawn on to the battlefield - but when a Welsh prisoner of war is brought to him for treatment of a sword-wound, he finds himself embroiled in the conflict. The young soldier is the foster son of the Prince of North Wales, and a prized possession. In fact, he is so valuable that he can be offered in exchange for Gilbert Prescott, the Sheriff of Shrewsbury, who has been captured by the Welsh.

A swap is duly arranged, but when one of the prisoners is found dead before the transaction takes place, the community learns the horrifying truth: there is a murderer in the monastery. Can Cadfael find out who it is?