The fourth anniversary of the transfer of Saint Winifred's bones to the Abbey at Shrewsbury is a time of celebration for the 12th-century pilgrims gathering from far and wide. In distant Winchester, however, a knight has been murdered. Could it be because he was a supporter of the Empress Maud, one of numerous pretenders to the throne? It's up to herbalist, sleuth, and Benedictine monk Brother Cadfael to track down the killer in the pious throng.