Free medieval romance from Patricia Ryan, originally published in 1996:
Heaven's Fire
Spoiler:
Rainulf Fairfax—priest, Oxford scholar, and ex-soldier—is summoned to give last rites to a village rector who died of smallpox, and discovers Father Osred's lovely young housekeeper, Constance, near death from the same disease. With Rainulf's help, she recovers, only to find herself at the mercy of the village's brutal overlord, who means to make her his unwilling mistress. Disguised as a male, she escapes to Oxford in search of Rainulf, who offers her the protection of his home. Inexorably drawn to each other, the celibate Rainulf and the beautiful and vibrant Constance find themselves swept into a firestorm of forbidden passion. Originally published by NAL