Shatterproof is the fourth book in the Cahills vs. Vespers series and was available on September 4, 2012, along with Card Pack 2: The Magellan Heist. It is written by Roland Smith, who has written many book including the I.Q. series, Peak, Cryptid Hunters series, Tentacles, and more, but this is his first The 39 Clues book. The mission unlocked with the cards from this book reveals Vesper Three, "The Mole".