Lady Mary's past catches up with her when an unwelcome visitor delivers an ultimatum, and news about the running of Downton Hospital puts Violet on the warpath.
Downton Abbey opens its doors to the public for charity, Barrow's actions are misconstrued, Mary and Henry's romance blossoms, and tensions between Cora and Violet reach a dramatic climax.
Mary endeavors to build bridges with her sister while Edith's secret continues to pose a threat. As Henry settles into the role of husband and stepfather, finding his place at Downton proves more difficult.