Dominican friar Etienne de Bourbon visits a 13th-century French village in search of heretics for the Inquisition. Despite the opposition of the local priest and the indifference of the villagers, he finds a seemingly perfect suspect: a young woman who lives in a forest outside the village and cures people with herbs and folk remedies. In the process, he discovers the cult of the greyhound "Saint" Guinefort, and confronts his own troubled past.

L'histoire, inspirée d'une anecdote du XIIIème siècle, d'une jeune guérisseuse accusée de sorcellerie qui réussit, grâce a son immense générosité, à attendrir un redoutable inquisiteur.