NEW YORK (March 2, 2013)--Shirley MacLaine will return to "Downton Abbey" next season, and opera star Kiri Te Kanawa will join the cast, producers say.

Carnival Films and "Masterpiece" on PBS say MacLaine will reprise her role as Martha Levinson, Lord Robert Crawley's freewheeling American mother-in-law.

The world-renowned soprano will sing.

Meanwhile, the producers confirmed that villainous housemaid Sarah O'Brien won't be back.

Siobhan Finneran, who played her, is leaving the series.

The announcements Saturday followed the third season's recent airing in the United States.

The season concluded last month with the death of popular character Matthew Crawley, thanks to departing cast member Dan Stevens.

Lady Sybil Branson also died.

She was played by the exiting Jessica Brown Findlay.