Sarah O'Brien, known primarily as Miss O'Brien, is Lady Grantham's personal maid. She is quite a bitter and resentful person, often scheming to get others into trouble for no good reason other than the fact that it's just the way she is. Early on, she and Thomas connive together to manipulate events to their own benefit. They worked together to try to get Bates fired shortly after his arrival and have assisted each other in various other schemes. If Miss O'Brien is crossed, there will be repercussions -- even when it comes to Lady Grantham, the person to whom she is solely responsible for watching over.Miss O'Brien's bitterness could stem from the fact that her one beloved brother had shell shock and later died during the Great War. As a possible example of her devotion to her family -- or just another way to advance her own interests -- Miss O'Brien convinced Mr. Carson to give her nephew, Alfred, a job as a footman. Whether due to guilt over her actions or a real understanding of their consequences, Miss O'Brien may ultimately seek to reevaluate her choices.