'Downton Abbey' loses O'Brien, adds 6 new cast members in Season 4 "Downton Abbey" is going to look quite different when it returns for a fourth season. On Friday Siobhan Finneran -- better known to fans as O'Brien, Lady Grantham's constantly scheming, severely coiffed maid -- confirmed that she is leaving the beloved costume drama. Finneran follows co-stars Dan Stevens and Jessica Brown Findlay out the door, though it seems likely her character will do so under less tragic circumstances than theirs: In the Season 3 finale, O'Brien was jockeying hard for a new job that would allow her to see more of the world. O'Brien's exit can only come as good news to the Grantham family, who over the years have repeatedly fallen victim to O'Brien's cruel machinations - most notably in Season 1 when her ladyship, pregnant with a long-awaited male heir, slipped on a strategically placed bar of soap and miscarried. PHOTOS: On the set of 'Downton Abbey' Finneran's departure may be felt more acutely by fans who will no doubt miss O'Brien's snide cutdowns and seemingly insatiable appetite for revenge. But fear not: Over the weekend Carnival Films, producers of "Downton Abbey," announced that six new cast members will be joining the series when it returns for a fourth season. Surely there will be at least one delightfully wicked character among the new crop: Opera singer Dame Kiri Te Kanawa will star as a guest who comes to perform at the Crawley family home, while Dame Harriet Walter, a veteran actress known for playing snooty, upper-crust types in films such as "Atonement" and "Sense and Sensibility," will appear as Lady Shackleton, a friend of the Dowager Countess. For those of you keeping track, that brings "Downton Abbey's" dame tally to three. In what may be the most interesting addition to the cast, Tom Cullen, brooding star of the acclaimed indie drama "Weekend," will join the cast as Lord Gillingham. In the announcement, his character was billed simply as "an old family friend of the Crawleys who has known Lady Mary since childhood" but is widely rumored to be the widow's new love interest. PHOTOS: 'Downton Abbey' Season 3 portraits Rounding out the new batch are Nigel Harman as a visiting valet, Joanna David as the Duchess of Yeovil and Julian Ovenden as an aristocrat named Charles Blake. Carnival Films also released a publicity photo of Lady Mary (Michelle Dockery) holding her infant son -- yet another fresh face, though one less likely to replace O'Brien as the show's resident villain. While there was no word about the rumored addition of a black cast member, producers did confirm that Shirley MacLaine, who made a brief appearance as Lady Grantham's mother in Season 3, will also be returning in the upcoming Christmas special. 'Downton Abbey' recap: Ending on a (very) down note SAG Awards give 'Downton Abbey' cast a proper welcome 'Downton Abbey' will reportedly add a black character in season 4