O'Brien is leaving "Downton Abbey," but not without creating drama that will ripple throughout the popular PBS series.


"Mrs. Hughes is tasked with the real headache of finding another lady's maid for Lady Cora," Phyllis Logan, Mrs. Hughes to "Downton" fans, told TV Guide. "But someone interferes and ends up taking the decision out of Mrs. Hughes's hands, which is totally wrong. My toes get stepped on!"


O'Brien's exit will take Cora (Elizabeth McGovern) by surprise. "Well, O'Brien’s departure is a minor trauma, but it takes on an even greater proportion as a displacement for the major trauma, which is of course the hole created by Matthew’s death," McGovern said.


Siobhan Finneran, the actress behind the nefarious O'Brien, will appear in one episode of "Downton Abbey" Season 4 to wrap up her story, TV Guide reports.


"I was devastated," Rob James-Collier (Thomas on "Downton Abbey") said of Finneran's exit. "She's the best actor I’ve ever worked with. I’ve not worked with many so it’s not much of a badge of honor! But she was brilliant. She was also really funny and we were really good friends. Really strong character, a very funny woman, brilliant actor."


As for why O'Brien is leaving her post, viewers will have to watch to find out. Finneran has been more public about why she's leaving. "I signed up to do three series and that was all I wanted to do," she said. "I had great fun doing it but I just didn’t want to do it any more. I decided this before we even did the last series. When I stop loving something, I stop doing it."


"Downton Abbey" Season 4 premieres in the US on Sunday, Jan. 5, 2014.



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  • Lady Mary and Brason


    "Downton Abbey" Season 4




  • Daisy


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  • Lady Mary


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  • Branson and Sybil


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  • Season 4 cast: Tom Cullen


    Cullen will play Lord Gillingham, a family friend of the Crawleys who visits the family as a guest at a house party. He's <a href="http://www.huffingtonpost.com/2013/03/02/downton-abbey-lady-mary-boyfriend_n_2796504.html?utm_hp_ref=tv" target="_hplink">one of Lady Mary's potential suitors</a>, along with ...




  • Season 4 cast: Julian Ovenden


    Ovenden will play aristocrat Charles Blake, <a href="http://www.huffingtonpost.com/2013/03/02/downton-abbey-lady-mary-boyfriend_n_2796504.html?utm_hp_ref=tv" target="_hplink">another potential love interest for Lady Mary</a>.




  • Season 4 cast: Dame Harriet Walter


    Walter will play Lady Shackleton, an old friend of the Dowager Countess.




  • Season 4 cast: Joanna David


    David will appear in a guest role as the Duchess of Yeovil.




  • Season 4 cast: Nigel Harman


    Harman will play Green, a valet.




  • Season 4 cast: Dame Kiri Te Kanawa


    Te Kanawa will play a guest who sings in the house.




  • Season 4 cast: Shirley MacLaine


    Shirley MacLaine will also return for the Season 4 finale.




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