Mariam was Cadfael's Syrian lover, a widow who ran a small fruit stand in the market. She was a Muslim, but this didn't seem to create any difficulties between her and the devoutly Christian Cadfael.
After Cadfael's departure from the Holy Land, she gave birth to his son, Oliver de Bretagne. Though she never told Oliver his father's name, she praised him extensively. She died some time before the series.