Set in December 1919 and January 1920. The household is bustling with all the Christmas preparations. The servants are having luncheon in the servant’s hall and Sir Richard Carlisle questions why they do not serve lunch upstairs as usual. Edith inquires whether or not Sir Anthony is invited for the New Year’s Day shoot. Rosamund had Lord Grantham invite Lord Hepworth who gets a disapproving look from the Dowager, who knew his father in her youth.
Matthew gets news that Lavinia's father is dying and he must go down to London. Miss O'Brien takes a Ouija board from Daisy and begins to play it in the servant’s hall. Meanwhile, Mary and the family are playing charades upstairs.
Lady Violet invites Sir Anthony to her house while Edith is there. He shows his injured arm to explain why he would not come to the shooting. Edith seems excited to see him.
December 31, 1919: After Lord Hepworth arrives, Cora receives a letter from Sybil with the news of her pregnancy. Lord Grantham says they have “Crossed the Rubicon.” Cora are replies jokingly that when the Revolution comes, they'll know someone on the other side. The family and servants toast the New Year.
January 1,1920: The men go out hunting pheasant and Matthew extricates lady Mary from Sir Richard. Cora finally informs Lord Grantham on the missing detail about Lady Mary's engagement to Sir Richard Carlisle. despite his threatening to reveal her dark secret regarding Kemal Pamuk.
January 8, 1920: Mr Bates is put on trial for the murder of his ex-wife Vera. Lord Grantham and Mrs. Hughes testify, but Bates is not portrayed in a good light and the evidence for prosecution look much more convincing than for the defense. Bates is found guilty and sentenced to be hanged. Anna breaks down and decides that she will have to leave Downton if worst comes to worst. Matthew tells Anna there's still a chance to fight, and later the death sentence is commuted to life imprisonment. Mary finds her father in the library deeply saddened over the result of Bates' trial. Lord Grantham then confronts Lady Mary about the 1913 Pamuk Scandal and convinces her that she shouldn't marry Richard. He tells her to go to America and live with Grandmama until the fuss dies down. He proclaims he doesn't want his daughter to live a life of misery and ruin. He wants a brave man for her. "Find a cowboy in the Middle West and bring him back to shake us up a bit." At this, Mary and Robert embrace.
January 10, 1920: Mary decides that she will go to America and stay with her grandmother until the scandal blows over. Mary then tells Matthew about Pamuk, knowing that he'll have to find out eventually and is surprised to hear that Matthew isn't worried about it.
January 11, 1920: Mary breaks with Carlisle. Sir Richard tells Mary he has kept her "filthy scandal" safe from prying eyes. He asks her "why did the papers leave [her] alone over Bates? Why has there been nothing linking to the great Earl of Grantham?" She comes to the conclusion that he stopped it, whereupon Carlisle reveals he has kept it secret with threats, bribes and calling in favors. Matthew, who has been listening in enters to see if Mary is all right? "I heard shouting." Sir Richard insults Lavinia's memory to Matthew over how false her love for him was, causing a brief scuffle and a broken vase. Robert enters and demands the brawl to end. Sir Richard then at his wits end insults Robert. "How smooth you are. What a manner of manners and elegance. I wonder if you will be quite so serene when the papers are full of your eldest daughter's exploits."
January 12, 1920: In the morning, Sir Richard prepares to leave. Mary comes down to see him off despite the previous nights exhibition. Sir Richard proclaims he truly felt love for Mary and she gives him hopes that the "next woman deserves [him], more than [she] did."
After dancing with Mary for a while at the Servant's Ball, Mathew tells her that they both lived their lives in different ways and it's in the past. Finally, Matthew proposes to Mary, but only after she insists he get down on one knee. She then accepts.
- So far, this episode and the 2015 Christmas Special are the only two Downton Christmas Specials actually set at Christmas.
- Violet uses the phrase Mais où sont les neiges d'antan? quoting the French poem Ballade des dames du temps jadis. It literally translates to Where are the snows of yesteryear?, or more figuratively, Why does life fade so quickly?.
- Robert says that Sybil has crossed the Rubicon. Roman law at the time of Julius Caesar made commanding troops into Italian territory a capital offence. When Caesar had his troops cross the river Rubicon in 49 BC, he was irrevocably committed to his actions, hence the origin of the phrase.