This is the story of the most significant devotional author of the seventeenth century in his first full English language biography. Using previously unknown letters as a few of the resources, this story aims to recreate the theological, sometimes magical, and social worlds of Johann Arndt. Arndt was regarded by his peers and successive generations as either the most significant Reformer since Luther, or an uneducated and dangerous element within the Lutheran church. Later commentators have given Arndt the credit, or blame, for the founding of the Pietist movement. Arndt was a central figure in the forging of various Lutheran “orthodoxies” of the early seventeenth century and thus the first generation to attempt an interpretation of the Lutheran Confessions of Faith. He is challenged by some on the conservative right for his mystical influences, but was a hero to orthodox Lutheran Johann Gerhard. He did more than found the pietist tradition (which he actually may or may not have); he also became the father of a Lutheran spiritual, maybe mystical tradition. While this movement would only last in more extreme forms of the Lutheran church, the argument from Arndt, Gerhard, and others was that this tradition was not in conflict with the teachings of the Lutheran Confessions. It’s a movement that almost was, and lives on in whispers in the church today.