In a tiny, dilapidated trailer in northeastern Oregon, a young Mexican woman sees a vision of the Virgin Mary. After being met with scepticism from the local parish, the Catholic diocese officially places the matter 'under investigation'. Journalist Randall Sullivan wants to know how exactly one might conduct the official inquiry into such an incident and sets off to interview 'the miracle detectives'. These are the theologians, historians and postulators from the Sacred Congregation of the Causes for Saints who are charged by the Vatican with testing the miraculous and judging the holy. Sullivan's investigation leads from Vatican City in Rome via Lourdes to the tiny village of Medjugorje, where six visionaries have been receiving apparitions of the Virgin Mary over a number of years. An examination of the longest-running Marian apparitions in history, and the author's own faith and beliefs as he himself becomes a miracle detective, are at the heart of Randall Sullivan's stunning new book.