The apostle Peter is a pillar of the church whose writing has been overlooked until recently when scholarship remedied this gap, significantly elevating Peter's letters. However, one critical area has been omitted. Within the Petrine writing is a robust, empowered, and beautiful mystical theology, which makes Peter an unexpected but vital Christian mystic. In exploring his love of artwork, German theologian and priest Romano Guardini developed the Threefold Seeing, which has been brought to light by Yvonne Dohna Schlobitten of the Pontificate Gregorian University. His unique method of viewing the artist, artwork, and observer develops a way of encountering the world and word. Instead of looking at the world or the biblical text through separate vantage points, the Threefold Seeing integrates all disciplines under greater view of God, the artist of all creation. The Letters of an Unexpected Mystic employs Guardini's Threefold Seeing to encounter the mystic Peter and the Petrine mystical theology. The result is a book that provides its readers with a means to become the Christian Karl Rahner wrote about in 1971: "The devout Christian of the future will either be a 'mystic,' one who has 'experienced' something, or he will cease to be anything at all."