The Raven in the Foregate by Ellis Peters

It is Christmas, A.D. 1141, Abbot Radulfus returns from London, bringing with him a priest for the vacant living of Holy Cross, also known as the Foregate. The new priest is a man of presence, learning, and discipline, but he lacks humility and the common touch. When he is found drowned in the millpond, suspicion is cast upon a young man who arrived with the priest's train and was sent to work in Brother Cadfael's garden. Indeed, he is soon discovered to be an impostor. To Brother Cadfael, now falls the familiar task of sorting out the complicated strands of innocence and guilt.
 
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