Cadfael meets The Name of the Rose in a medieval eastern European village when two young adults encounter a witch in a wooded glen.
Eric and Julia seek tree grafts to help their families' orchards. When darkening skies and distant thunder tell of an approaching storm, Eric motions them back home. Sullya, a witch hidden in the trees, grabs Julia as they walk past. Eric swings his axe and severs Sullya's hand. Wounded, Sullya seeks refuge in the deep bole of an old oak in the center of the glen. Her hand falls onto the same oak and crawls up the trunk to join her.
The sky opens with heavy rain. Eric wants to flee but Julia, believing they're safe, torments the witch. Sullya safely hid in the old oak, curses them, their families, their crops, their livestock, and their village.
Soon crops wilt, livestock die, and much of village falls ill. The village priest, Father Baillot, seems ignorant of church ways and proves ineffective against the curse.
The village elders seek help elsewhere, specifically from a distant priest, Father Patreo, who knows the Old Ways as well as the New. Patreo is out of favor with the Church because he makes no effort to hide his belief that progress comes from exploring all paths, not just those the Church decrees acceptable.
He and Verduan, one of the village elders, investigate the witch and her curse, encountering espionage, treason, witchcraft, demons, religious persecution, mistaken identities, and fear of what was and what will be, and what they discover changes the face of Eastern Europe forever.