O'Brien's Departure

In the first ep of last season, she suddenly resigned without notice and just left a note for Lady Cora and a film double was used to see the back of "O'Brien" leaving with a suitcase in the middle of the night without anyone knowing. Lady Cora was very miffed that O'Brien left without notice and without a replacement already in place after all her years of service to Lady Cora, and while we the audience know of all her perfidies and while the O'Brien character was written to be a better and less spiteful character in successive seasons, Lady Cora still considered O'Brien a friend and was very hurt at her sudden departure. I don't remember what the note said, but probably something vague about her wanting to "move on" as the whole "O'Brien leaving" thing wasn't given much time. They usually play the series several times before the start of the next season or you can find it online to watch that ep if you want more particulars of what exactly was in the note -- but it didn't really stand out and they quickly moved on to finding a replacement and wouldn't you know it but sneaky Thomas had a woman handy for the position, over whom he has some hold which is hinted at all season but never explained. So I guess we'll learn what that hold is the next season. So far the woman has avoided giving away any of the family and Lady Cora's secrets to Thomas despite his pressures and threats.

Hopes this helps.

Great explanation. But, specifically the note said that she'd gone to work for Roberts cousin, Roses' mother. That roses' mother booked her passage to India, and she felt it too good a chance to pass up. Remember, it was hinted at that Robert cousin really like the way O'Brian did her hair when they all visited and Obrien was her as a lady's maid there.