The third season also saw the shocking death of Lady Sybil Branson, who died during childbirth. She was played by the departing Jessica Brown Findlay.
Last season the wildly popular melodrama, set in early 20th century Britain, was the most-watched series on PBS since Ken Burns' epic "The Civil War," which first aired in 1990. The Nielsen Co. said 8.2 million viewers saw the "Downton" season conclusion.
"Downton Abbey," which airs on the "Masterpiece" anthology, won three Emmy awards last fall, including a best supporting actress trophy for Maggie Smith (the Dowager Countess), who also won a Golden Globe in January.
In all, the series has won nine Emmys, two Golden Globes and a Screen Actors Guild Award for the ensemble cast, which is the first time the cast of a British television show has won this award.
Hugh Bonneville, Michelle Dockery, Elizabeth McGovern, Jim Carter and Brendan Coyle are among its other returning stars.