July 1209: in Carcassonne a young girl is given a mysterious book by her father which he claims contains the secret of the true Grail. Although Alaïs cannot understand the strange words and symbols hidden within, she knows that her destiny lies in protecting it. It will take great sacrifice and faith to keep the secret of the labyrinth safe - a secret that stretches back thousands of years to the deserts of Ancient Egypt . . .

July 2005: Alice Tanner stumbles upon two skeletons during an archaeological dig in the mountains outside Carcassonne. Inside the hidden tomb where the bones lie crumbling, she experiences an overwhelming sense of malevolence, as well as a creeping understanding that, however impossible it seems, she can somehow understand the mysterious ancient words carved into the rock. Too late, Alice realises she's set in motion a terrifying sequence of events that she cannot control and that her destiny is inextricably tied up with the fate of the Cathars 800 years before.