Early 13th century, Europe. The time of the Crusades, the fight against heresy, secret societies, alchemists and warlocks. Two old friends-companions, collecting occult relics and valuable books in the countries of the East and selling them to believers and the powers that be, after one of the transactions began to be pursued by emissaries of the secret tribunal of St. Thema. To escape pursuit, they are forced to separate and lose sight of each other for a long time. But one of them, Vivien de Narbon, is left with a sacred book with a spell of power, which is hunted by people in red masks, and his partner, Ignacio from Toledo, finds a cryptogram left for him with secret clues about the book and, having solved it, sets off again on a journey...