Character: Sarah O'Brien
(played by Siobhan Finneran)
O’Brien is Lady Grantham’s lady’s maid. She is a bitter woman who seems to delight in thinking the worst of others. Her only ally on the staff is Thomas, with whom she plots to get others into trouble and advance Thomas’ career. After her behavior causes Cora’s miscarriage, she becomes racked with guilt and devoted to protecting her. She also shows a softer side protecting the shellshocked Lang (one of her brothers suffered from the same condition).