Sophie Turner has joined the cast of the HBO Max series “The Staircase.”

Turner joins previously announced cast members Colin Firth, Toni Collette, Parker Posey, Juliette Binoche, and Rosemarie DeWitt.

The eight-episode series is based on the docuseries of the same name as well as various books and reports about the case of Michael Peterson (Firth), who was accused of murdering his wife, Kathleen (Collette), in 2001. He claimed she died after falling down the stairs at their home, but police suspected he bludgeoned her to death and staged the scene to look like an accident.

Turner will play Margaret Ratliff, one of Michael Peterson’s adopted daughters. Turner is best known for her role as Sansa Stark in the megahit HBO series “Game of Thrones.” Her time on the show earned her an Emmy nomination for best supporting actress in a drama. She is also know for playing Jean Grey...