Watch on Soap2day. This documentary discusses a mysterious priest named Berenger Sauniere who allegedly discovered a secret treasure in his church at Rennes-le-Chateau in southern France. The program takes a fanciful journey as to whether the treasure existed and what might have been its source. It also seeks to connect Sauniere with the mythological "secret society" known as the Priory of Sion. The 1982 book Holy Blood, Holy Grail and Dan Brown's 2003 novel The Da Vinci code are both inspired by the Rennes-le-Chateau myth.