Languedoc. Land of the Cathars, the last stronghold of the rebellious Templars. According to legends, somewhere here, in the labyrinths of caves, the mystical “Cathari Grail”, rescued from the castle of Montsegur, is kept. Do the legends lie? Probably... But just recently a mysterious cave was found in Languedoc , where the walls are completely covered with mysterious writings. And in its very heart is a mesmerizing bluish glow, the source of which is impossible to determine... On behalf of the UN, the study of this phenomenon is entrusted to historian Peter Lavell, engineer Patrick Nevro and linguist Stefanie Kruger. They get down to business, but soon a real hunt begins for them, in which they participate and intelligence services, and secret Catholic organizations and even members of ancient occult sects...