1919年6月，胜利阅兵式的欢庆队伍经过伊顿广场165号，但这座钟爱的贝拉米宅邸正面临前所未有的变革。随着一战结束，詹姆斯·贝拉米勋爵战死的阴影仍笼罩着这个家庭，而夫人海泽尔·贝拉米决定带着女儿露西搬离伦敦。宅邸被挂牌出售的消息在下人房引发震动——若新主人不需要服务团队，所有仆役将面临失业。 　　Rose和爱德华兹先生暗中筹划着未来，而执事哈德森太太则坚持"只要宅子还有一块砖，我们就要保持体面"。楼上的动荡与楼下的人心惶惶形成鲜明对比：厨娘佩里太太担忧养老金，年轻女仆黛西却对新时代充满期待。当富商巴克豪斯爵士表现出购买意向时，他提出的"现代化管理"方案更让传统仆役制度岌岌可危。 　　Meanwhile, the sudden return of wounded veteran Major Gregory Wilmot brings unexpected complications. His connection to Lady Marjorie's past resurfaces, forcing Hazel to confront buried secrets before leaving. Below stairs, footman Alfred's flirtation with a suffragette housemaid from next door sparks debates about women's rights, mirroring the social changes sweeping postwar Britain. 　　The season culminates in a bittersweet farewell dinner where upstairs and downstairs join together for the first time. As Hazel hands over the house keys, Hudson breaks protocol by toasting "not to masters and servants, but to those who made this house a home". The final shot lingers on the empty servants' bells, their silence marking the end of an era.