Sophie Turner is the latest star to join the cast of HBO's The Staircase

She found fame playing roles in Game of Thrones and X-Men. New role: Sophie Turner is the latest star to have join the cast of HBO's The Staircase - following the likes of Toni Collette and Colin Firth The Staircase is centered on novelist Michael Peterson who was accused of murdering his second wife, Kathleen in 2001. Also cast: The news of Sophie's latest role comes a month after both Colin Firth and Toni Collette were confirmed to have been cast The now-77-year-old author claimed that his spouse had died after falling down the stairs at their home in North Carolina, although police suspected that he had killed her and covered up his evidence. The news of Sophie's latest role comes a month after both Firth and Collette were confirmed to have been cast. Accused: The Staircase is centered on novelist Michael Peterson, who was accused of murdering his second wife, Kathleen, in 2001 The forthcoming series will be helmed by Antonio Campos, who will direct six episodes of the show, as well as writer Maggie Cohn.