July 2005. In the Pyrenees mountains near Carcassonne, Alice Tanner, a volunteer at an archeological dig, stumbles into a cave and makes a startling discovery -- two crumbling skeletons, a stone ring and a small leather bag. Too late Alice realizes that she has set in motion a terrifying sequence of events and that her destiny is inextricably tied up with the fate of those called heretics eight hundred years before.

July 1209. On the eve of a brutal crusade sent by the pope to stamp out heresy, a crusade that will rip apart southern France, seventeen-year-old Alais is given a ring and a mysterious book for safekeeping by her father as he leaves to fight the crusaders. The book, he says, contains the secret of the true Grail, and the ring, inscribed with a labyrinth, will identify a guardian of the Grail. As crusading armies led by the Church potentates and nobles of northern France gather outside the walls of Carcassonne, it will take great sacrifice to keep safe the secret of the Labyrinth, a secret that has been guarded for thousands of years.