In his historical novella, Gottfried Keller (1819-1890) draws on the religious conflicts between the Reformed and Old Catholic Swiss cantons at the beginning of the 16th century. When the reformer Zwingli attempts to enforce the Reformation in Zurich by force, the mercenary Hansli Gyr sides with him. However, this puts him in conflict with his fiancée Ursula, who belongs to the radical religious sect of the Anabaptists. Both are inexorably drawn deeper into the horrors of the religious war.