The eldest daughter of Robert and Cora, Mary is the sister of Edith and Sybil. She is loyal to Downton and will go to great lengths to save it and remain living there, having already had a marriage arranged with Patrick, a cousin who was the heir when the series began and news of Patrick's death on the Titanic changed everything. Early on, she is portrayed as a petulant and cold young woman, even questioning whether she should wear mourning clothes after learning of Patrick's death as she felt no real connection to her fianc