Two women in different time periods on a hunt to find/protect the Grail? That’s a fantastic premise! But unfortunately, the execution is a bit clumsy. With Oriane determined to get her hands on the books, it's up to Alaïs to smuggle the trilogy to safety. As the Viscount prepares for a siege, Alaïs's father decides to unite the three books and entrust them to his youngest daughter, much to the jealousy and resentment of her elder sister Oriane. To complicate matters, an army from the north of France is invading Carcassona in order to eradicate the Cathar heretics. With that discovery, her father reveals to her his long-held secret: that he is one of the guardians of three books that contain the secrets of the Holy Grail. One morning she goes to fetch herbs on the riverbank and discovers the dead body of a man in the water, his throat cut and his thumb removed.

In 1209, seventeen year old Alaïs is a newly-wed wife who lives with her husband, father and sister at Chateau Comtal, a citadel under the protection of the very young Viscount Raymond-Roger Trencavel. That’s an early warning that the historical-mystery element, involving both 13th-century knights and 21st-century Eurotrash villains seeking the Holy Grail, will be simultaneously harebrained and perfunctory.Alaïs and her crappy husband. Vanessa Kirby, meanwhile, plays the modern-day Alice, who starts the action by wandering into a cave during an earthquake on an archaeological dig and finding a ring while hearing Alaïs’s voice whispering to her across the years. Brown Findlay’s “Downton” character, Lady Sibyl, but it comes as much less a surprise. She has the bad timing to be there when crusaders arrive to dispatch the Cathars, who have been declared heretics. Jessica Brown Findlay of “Downton Abbey” toils in the medieval story line as Alaïs, a French noblewoman living in Carcassonne, the picturesque hill town. Perhaps the biggest problem with the show, adapted by Adrian Hodges (“Primeval”) from the Kate Mosse novel and directed by Christopher Smith, is that there isn’t enough story for four hours - even though there are parallel plots taking place in 12, each with its own full cast of mostly British actors.

Always wanted to know more about Catharism and the Albigensian Crusade? After watching “Labyrinth,” you may actually know less.

CW starts off the summer television season on Thursday night with “Labyrinth,” a “four-hour event mini-series.” “Event” in this case means a two-year-old “Da Vinci Code” rip-off from the Ridley Scott costume-drama factory.

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