特别篇开始，Mary（米歇尔·道克瑞 Michelle Dockery 饰）已经怀孕，一家人到苏格兰Rose家度假，留在庄园的Tom（艾伦·里奇 Allen Leech 饰）在Isobel和新女仆Edna的劝说下和众仆人打成一片，令管家Carson（吉姆·卡特 Jim Carter 饰）颇为头痛。没有了主人的仆人们似乎生活更加轻松和随意。众人一起去了集市，而Jimmy对Thomas（罗伯·詹姆斯-克里尔 Rob James-Collier 饰）的态度也有所好转。杂货店老板Joss似乎对Patmore太太有着别样的感情。Gregson为了让Crawley一家接受他对Edith（劳拉·卡尔迈克尔 Laura Carmichael 饰）的感情也来到了Rose家，而Robert（休·博内威利 Hugh Bonneville 饰）发现老友一家似乎也面临了财政问题。终于，Mary平安生下儿子，Matthew（丹·史蒂文斯 Dan Stevens 饰）去医院看望完妻儿，欣喜地向家人报喜时，他的车不幸与一辆货车相撞......

处在贝茨先生（布兰登•柯伊尔 Brendan Coyle 饰）受审一事阴霾中的唐顿庄园迎来了1919年的圣诞节。战争虽已过去，但影响仍在持续。房屋能被装饰一新，但唐顿人的心情却仍无法放晴。大小姐玛丽（米歇尔•道克瑞 Michelle Dockery 饰）觉得和理查德的婚姻不会幸福，但仍然决定继续；马修（丹•史蒂文斯 Dan Stevens 饰）仍对拉维尼娅的死感到愧疚；老爷（休•博内威利 Hugh Bonneville 饰）得知了玛丽不得不嫁给理查德的原因。尽管烦恼的事不断，但仍有好事传来。茜玻（杰西卡•布朗-芬德利 Jessica Brown-Findlay 饰）写信来告知了自己怀孕一事；被宣判死刑的贝茨因为证据不足改为了无期徒刑。新年晚会在贝茨的好消息中如期举行。新的一年即将来临，一切都在变化中，包括马修和玛丽的关系…… 第三季将于2012年9月16日于当地时间首播。

The Great War rages across Europe, and not even the serene Yorkshire countryside is free from its effects. The men and women of Downton are doing their part both on the front lines and the home front, but the intensity of war only serves to inflame the more familiar passions: love, loss, blackmail, and betrayal.

Lord Robert Crawley and his family live a life of leisure, while a fleet of servants, including butler Carson, attend to their every need. But two events conspire to shake things up: the sinking of the Titanic, which claims Crawley's heirs, and the return of his valet, Bates. Since Crawley and Lady Cora have three daughters, his distant solicitor cousin, Matthew, becomes heir to the estate. With that, the scheming begins, since Thomas the footman views Bates as an interloper and Crawley's mother, Violet, feels the same way about Matthew's mother, Isobel.