Martin Luther begins as an Augustinian monk terrified for his own salvation, and ends as the man who split western Christianity in two. The film follows him from his early crisis of faith to the night in 1517 he is said to have posted 95 theses on a Wittenberg church door, attacking the sale of indulgences by the Catholic Church. It traces his refusal to recant before Emperor Charles V at the Diet of Worms, his excommunication, and the years in hiding at Wartburg Castle where he translated the New Testament into German, putting scripture into ordinary readers' hands for the first time. Central to the account is Luther's doctrine that faith alone, not clerical mediation, secures salvation, an idea that turned a monk's personal doubts into a continent-wide rebellion against Rome. The title's tension runs through the film: a reluctant participant in a reformation he did not set out to start.