It began as an intriguing piece of puzzle-solving - and ended with the discovery of the greatest secret of all. Dissatisfied with the explanations of previous researchers, Richard Andrews and Paul Schellenberger applied mathematical logic to the enduring mystery of the Rennes-le-Chateau and the 'treasure' alleged to be buried there. The quest began with an investigation into the activities of a group of 19th century priests who had become embroiled in the legend. These priests had grown rich because of their involvement and had maintained the anonymity of the paymasters, but in 1993 an extraordinary clue came to light which suggested the priests were engaged in activities at odds with traditional Roman Catholic pastimes. A series of paintings was unearthed which incorporated a cryptic, obscure geometry; a set of interrelating shapes with a very direct link to the priests' habitat and spiritual role. Through the centuries a pattern emerged - a web of concealment on maps, in fine art, on tombstones which defied coincidence and pointed to one very specific location...