- Writers: Julian Fellowes
- Stars: Allen Leech , Brendan Coyle , Dan Stevens , David Robb , Elizabeth McGovern , Hugh Bonneville , Jim Carter , Joanne Froggatt , Kevin Doyle , Laura Carmichael , Lesley Nicol , Lily James , Maggie Smith , Michelle Dockery , Penelope Wilton , Phyllis Logan , Raquel Cassidy , Rob James-Collier , Siobhan Finneran , Sophie McShera
April 1919. As Downton Abbey prepares for Lavinia and Matthew's wedding, Sybil and Tom shock the family by announcing their intention to move to Dublin, where he has work, and marry. However, events are overtaken and the marriage is put on hold when Carson, Cora, Lavinia and others fall sick with the Spanish flu. Thomas uses the situation as an excuse to get his job back but Lavinia, aware of Matthew's feelings for Mary, suggests that the marriage be called off. After admitting their mutual feelings, Jane gives Robert her resignation, her young son's future assured thanks to the earl, whilst Ethel decides to keep her son Charlie rather than give him to the Bryants, who would raise him to forget her. The flu goes away, having claimed one victim, and Robert finally gives Sybil and Tom his blessing as they leave for Ireland. Anna and John also marry, by special license. However, the day after the wedding they receive unwelcome visitors.