In the summer of 1144, Brother Cadfael departs once again from his monastery. This time, his companions include Helent, a young woman desperately trying to escape from a marriage arranged for her, and young Brother Marco, who represents the bishop in a matter of ecclesiastical diplomacy.

Cadfael does not anticipate any troubles on this mission, but during their journey, the three travelers unwittingly get entangled in the conflict of the Lord of Wales, Owen Gwynedd, with his treacherous brother Cadwalladr. The latter allies with a fleet of Danish mercenaries in order to crush Owen.

[Excerpt from the text on the back cover of the edition]