The first book in Ellis Peters's series, The Brother Cadfael Chronicles, is A Morbid Taste for Bones. The story takes place in the fictional Shrewsbury Abbey in 1137 A.D. After a full and varied life including participation in the Crusades, Cadfael returned to his native land, Wales, and has found a different calling as a monk, gardener and herbalist.
Brother Cadfael is chosen to go on a trip to retrieve the bones of local Saint Winifred. He gets involved in investigating a local murder -- in part because of his history and experience with violent deaths from when he was a soldier.
The next book in the series is One Corpse Too Many.