Harriet Walter (Law & Order: UK) joins the cast as the costume drama returns. Following Matthew's shocking death, new mother Mary is struggling to come to terms with her loss, and Robert and Violet disagree over how to handle the situation. Downstairs, Jimmy finally takes an interest in Ivy, while Carson receives an unwelcome reminder of his past. Mrs Hughes sees a chance to help grief-stricken Isobel, and Thomas has the children's nanny in his sights.