BERLIN — John Hurt and Sebastian Stan (“Captain America: The First Avenger”) are toplining “The Labyrinth,” the TV adaptation of Kate Mosse’s medieval bestseller about a quest for the Holy Grail.

British helmer Christopher Smith (“Black Death”) is directing the four-hour event miniseries, which tells two connected stories set 800 years apart — that of a modern-day archaeologist who makes a startling discovery in a cave in the south of France, and that of a young woman living in nearby Carcassonne in 1209. A stronghold of the outlawed Cathar Christians, the city becomes a military target after the Catholic Church declares the sect heretical.

Adrian Hodges (“Primeval”) is penning the series, a German-South African co-production between Tandem Communications, Scott Free Films and Film Afrika Worldwide in association with Universal Production Partners.

Set for delivery in summer 2012, “Labyrinth” was commissioned by Germany’s Sat.1 and the U.K.’s Channel 4. Other partnering networks include Spain’s Quatro, Austria’s ORF and France’s M6. Also on board are NBC Universal Home Entertainment and Germany’s Koch Media.

“The elements we’ve put together on ‘Labyrinth’ build on our strategy to create primetime event programs with cinematic values that work internationally: a worldwide bestselling book, a top writer for the adaptation, a cinematic director and an outstanding cast,” said Tim Halkin, exec producer and Tandem’s co-managing director.

Exec producer Ridley Scott of Scott Free added, “I’m very excited about the collaboration of two incredibly strong artists on this project: putting Adrian Hodges and Chris Smith’s talents together has become explosively exciting. We’re entering into principal photography with a film that you can already ‘see’ on the page.”

Also set to star are Janet Suzman, Jessica Brown-Findlay (“Downton Abbey”), Vanessa Kirby (“Great Expectations”), Katie McGrath (“Merlin”), Emun Elliott (“Game of Thrones”) and Claudia Gerini.

“Labyrinth” will begin principal photography in October in Carcassonne and in the Aude Cathar country in the south of France and later move to South Africa.

Mosse’s novel has been published in more than 38 languages, making both the New York Times hardcover and paperback bestseller lists, as well as becoming the U.K.’s bestselling fiction title of 2006.