Book excerpt: In the Mirror of the Prodigal Son provides a comprehensive history of the function of the parable of the prodigal son in shaping religious identity in medieval and Reformation Europe. By investigating a wealth of primary sources, the book reveals the interaction between commentaries, sermons, religious plays, and images as a decisive factor in the increasing popularity of the prodigal son. Pietro Delcorno highlights the ingenious and multifaceted uses of the parable within pastoral activities and shows the pervasive presence of the Bible in medieval communication. The prodigal son narrative became the ideal story to convey a discourse about sin and penance, grace and salvation. In this way, the parable was established as the paradigmatic biography of any believer.