Shirley MacLaine Will Return to ‘Downton Abbey,’ But Others Are Leaving the Series

Nick Briggs/Carnival Film and Television Limited 2013 for Masterpiece Michelle Dockery as Lady Mary in a scene from “Downton Abbey.”

The revolving door of casting continues to spin at “Downton Abbey” as that popular PBS/”Masterpiece” period drama prepares for its fourth season. After a year in which the series lost the actors Dan Stevens, who played Matthew Crawley, and Jessica Brown Findlay, who played Lady Sybil (for reasons that the “Downton Abbey” creator Julian Fellowes explained here), PBS announced over the weekend that some new faces would join the series and that a familiar one was returning. But another well-known co-star has also announced her exit.

Shirley MacLaine, who appeared in Season 3 of “Downton Abbey” as Martha Levinson, the outspoken mother of Cora, Countess of Grantham (Elizabeth McGovern), and who served as a foil to the Dowager Countess (Maggie Smith), will return in Season 4, PBS said. Several new actors were announced for the series, including Tom Cullen, whose character, Lord Gillingham, is described as “an old family friend of the Crawleys who visits the family as a guest for a house party”; Harriet Walter who will play Lady Shackleton (“an old friend of the Dowager”); and Julian Ovenden as Charles Blake (an “aristocrat”). The s! oprano Kiri Te Kanawa will also appear on “Downton Abbey” as “a guest who sings in the house.”

Nick Briggs/PBS, via Associated PressShirley MacLaine as Martha Levinson in, “Downton Abbey.”

No further information was given about these characters or a premiere date for Season 4. In a brief statement, Rebecca Eaton, the executive producer of “Masterpiece,” said, “The addition of these characters can only mean more delicious drama â€" which is what ‘Downton Abbey’ is all about.”

The announcement did not mention the actress Siobhan Finneran, who plays the Machiavellian housemaid Mrs. O’Brien, and who told The Daily Mirror of London that she was leaving “Downton Abbey.” “I’m not doing any more,” Ms. Finneran said. “O’Brien is a thoroughly despicable human being â€" that was great to play.” Though Mrs. O’Brien’s essential function was making life miserable for the “Downton Abbey” household, Ms. Finneran did not indicate that this played a role in her departure. “I actually have great fun being sniffy to everyone,” she said.

Meanwhile, Seth Meyers, the “Weekend Update” anchor of “Saturday Night Live,” addressed various reports and rumors that “Downton Abbey” would be adding its first black character to the series.