Father Ignaz (Ygnacio) Pfefferkorn, a missionary from the Sonora Desert region of northern Mexico, is caught in the expulsion of all Jesuits in 1767. After enduring eight years of prison and abuse, he is incarcerated in La Caridad Monastery where the abbot recruits him to help solve two murders. In the course of his investigations, Father Ignaz finds his own life in peril.