Jessica Brown Findlay is to star in a new BBC adaption of Jamaica Inn.
The former Downton Abbey actress will play the lead character Mary Yellan in the new TV adaptation of Daphne du Maurier's classic thriller.
Jessica found fame as Downton's Lady Sybil, the wild youngest daughter of Lord and Lady Grantham, who eloped with the chauffeur and ended up dying in childbirth in the last series.
Jamaica Inn, published in 1936, is set in Cornwall in 1820. Young heroine Mary is sent to live with her aunt at the inn after the death of her mother and discovers it to be the centre of a smuggling ring.
Philippa Lowthorpe, the director, said: "I love Jamaica Inn because it is an exhilarating adventure story set in a wild landscape with brilliant characters, and at its heart is Mary Yellan, a fantastic female heroine.
"I am delighted that Jessica Brown Findlay is going to play this bold and opinionated, courageous but naive young woman, whose curiosity and fiery nature get her into big trouble."
Since Jessica, 24, left Downton last year she has appeared in Channel 4 period drama Labyrinth, adapted from Kate Mosse's international best-seller.