Jakob Ziegler, the son of a wine merchant, experiences the eve of the Reformation as a Latin student in Neustadt an der Haardt and as a student in Heidelberg. Initially trapped in the fears of his time, he encounters the sale of indulgences but also the humanists, whose ideas inspire him. As a lawyer, he observes Martin Luther during the Heidelberg Disputation (1518) and at the Diet of Worms (1521), becoming embroiled in the wars against Franz von Sickingen (1523), against the peasants (1525), and in the persecution of the Anabaptists (1527). Ultimately, he finds the courage to forge his own path. He plays a role in the implementation of the Reformation in Hesse and is among the "Protestants" at the Diet of Speyer (1529) who, invoking their conscience, defended their faith against the Emperor and the majority of the imperial estates. The historical novel "The Protestant" sheds light on the period between 1500 and 15.