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......

Season 5 finds the Crawley family and the staff struggling with responsibilities and choices as they adjust to life in the Roaring Twenties. A new Labour government heralds changes that are being felt throughout the land, and Robert, Mary and Branson together must navigate these shifting sands to ensure the future of the estate for generations to come. As Branson finds himself playing a more crucial role at Downton than ever before, he can’t help questioning his place in this world. Mary is finally coming to accept that she would like to marry again, but will she ever be able to find the same happiness that she had with Matthew? Meanwhile with still no news of her beloved Gregson, Edith suffers under the burden of her terrible secret.

Downstairs, the servants are starting to consider what effect social changes may have on their working lives. While Daisy’s mind is opened to new possibilities, Mrs Patmore views such new and uncertain paths with trepidation. Anna and Bates have weathered many storms and are finally starting to plan their future. But with so much painful history, will they ever be able to completely move on, or will past secrets once again threaten their chance of ever finding happiness?