Two-hour Christmas special and the series finale. Mary endeavors to build bridges with her sister while Edith's secret continues to pose a threat. As Henry settles into the role of husband and stepfather, finding his place at Downton proves more difficult.
Aware of her secret, Bertie proposes to Edith. However, his morality-obsessed mother threatens to stand in their way, after Edith has confessed to her. Henry forsakes motor racing for a new venture with Tom. Molesley and Spratt also embark upon new careers and Barrow finds another position - with a curmudgeon - while Carson's health begins to fail. Isobel responds to some bad news from Lord Merton and Violet encourages her to thwart the plans of his greedy family. New Year's Eve 1926 sees, downstairs, romance flourishes.
- The Crawleys are taking a stroll around the estate. Mary notices Henry seems depressed and asks why. He has decided to give up car racing. Not because of what happened to Charlie, but because he no longer enjoys it. The question is, what will he do with his life now?
Edith has decided to make her home in London. Since she is a spinster, she must live her own life.
Mr. Dawes offers Molesley the classes and cottage of a teacher who is leaving. The cottage is owned by the Downton estate, which reserves the right to take it back if no one is living there. Molesley is unable to make a decision right away but Baxter assures Mr. Dawes that he will do so soon.
Baxter decides to throw away Coyle's letter and not visit him. By ignoring him, she will rid herself of his power over her.
Barrow finally has a job as butler on a nearby estate. Everyone wishes him well, including the children. He privately thanks Andy, Baxter and Anna for rescuing him and taking care of him after the suicide attempt. His new employers, Sir Mark and his wife, are elderly and have only a small staff. Barrow gradually becomes dissatisfied because there isn't much for him to do.
Carson spills wine due to tremors in his hand. Mrs. Hughes offers to make a doctor appointment but there is no need. Carson's father and grandfather suffered the same condition and it put an end to their careers. For now, they decide to say nothing to anyone.
Cora is very busy chairing meetings at the hospital. Robert feels neglected.
Edith calls on Spratt at the Dower House with news that his column, written under the name of Cassandra Jones, is a big success. She wants to make it a full page including fashion advice, of which Spratt is an expert. Denker listens outside the door and learns Spratt's secret. She taunts him by threatening to tell Violet. After Spratt insults her, she does tell Violet and shows her a copy of the magazine with Spratt's column. Denker expects that he will be dismissed at once but Violet loves the column and considers herself fortunate to have Spratt in her employ because now he can provide clothing advice.
Anna's pregnancy is progressing normally and her due date isn't far off. Bates wants her to stop working, but she wants to continue, with Baxter's help in doing the heavier work. Carson can't get used to the idea of a pregnant servant.
Henry discusses his future with Tom, including the need to find a job. He and George seem to be getting on all right, with Henry giving the child a piggy-back ride.
Edith accepts a ride to London with Henry. They discuss Mary and Henry says there are two Marys, his and Edith's. He drops her off at the flat, where an invitation awaits inviting her to dine that evening with Rosamund at the Ritz. But when they arrive at their table, Bertie is there. The meeting was obviously arranged and Rosamund leaves. Bertie confesses that Mary called him and set the whole thing up. Edith is angry, even when Bertie admits to wanting her back. She feels that his mother will not accept her once she knows the truth about Marigold. Bertie says they won't tell her. Eventually he persuades Edith to accept his proposal.
Robert and Cora are delighted with the news and prepare to visit Brancaster Castle for the engagement announcement. Mrs. Pelham is a formidable figure. She feels that the family has been tainted with rumors of immoral behavior, especially after the exploits in Tangiers of the late Lord Hexham. It is Bertie's task to live a moral life with no hint of scandal. Edith then feels that she must speak to Mrs. Pelham privately, which she does, and tell her the truth about Marigold. At first Mrs. Pelham is shocked and refers to Edith as damaged goods. Bertie means to marry Edith no matter what and his mother realizes she will have to give in. At the engagement dinner, she compliments Edith and welcomes her to the family. A wedding date is set for December 31, 1925.
Andy, having been rebuffed by Daisy, rebuffs her in return when she starts acting friendly. Mrs. Patmore scolds her, saying she couldn't find a better man. Daisy says cheekily that maybe she could. But now that Andy has seemingly lost interest, she wants him. She attempts to flirt when he is patching the roof at Yew Tree Farm but he doesn't respond. Fall is coming and the heavy work needs to be done at the farm, including separating the piglets from their mothers. Mr. Mason admits he could use Daisy's help in the house. But she is reluctant to be cut off from the goings-on at the house.
Edith asks Mary why she went to all the trouble of arranging the meeting with Bertie. Mary says they needed to be together and that she and Edith should make more of an effort to be friends.
Isobel learns that Lord Merton was taken to a London specialist by his daughter-in-law Amelia. The diagnosis was pernicious anemia, an invariably fatal condition. Devastated, Isobel admits to Violet that she is in love with Merton. She attempts to see him but is rudely turned away by Amelia. Violet thinks Merton is all but a prisoner and says it is because Larry and Amelia want to prevent Isobel from marrying him and thus having a claim on the estate.
This time with Violet, Isobel again visits the house. Amelia attempts to run her off but Lord Merton overhears the commotion. Isobel announces her intention of taking Merton to her home and not only nursing him but marrying him. Merton, having learned that Isobel had tried to see him earlier and not been admitted, is angry. Although he loves Larry as a son, he dislikes him intensely. He tells them the house is theirs and leaves with Isobel. They are eventually married although the ceremony is not shown.
Tom and Henry are busy planning something but won't say what. Barrow continues to be unhappy with his new job. Molesley decides to accept Dawes' offer and gives notice. Anna orders an electric hair dryer for Mary.
Daisy decides to change her image and borrows the hair dryer. After everyone is asleep, she washes her hair and attempts a stylish cut and style. But she doesn't know how to properly use the dryer and it turns her hair into a frizzy mess. The other servants laugh at her, including Andy, and she runs away in tears. Later, Anna helps to repair the damage and gives Daisy a becoming style.
Andy tells Daisy that they got out of step. If she wants it that way, so be it. If not, he would like it if they got back in step. Daisy agrees and later tells him she is moving to Yew Tree Farm.
Robert and Mary notice that something is wrong with Carson and confront him. He admits the truth and gives notice. Robert protests but Carson is adamant that he can no longer do his job. He will stay on long enough to interview and select a new butler, saying that he won't leave the family with just anyone. Robert says he will have a pension from the estate and can perhaps be on hand for big events, to advise and aid the new butler. Carson says that wouldn't be proper and he himself would not accept a job under those conditions.
Tom and Henry take Mary to York and show her a building with a sign, Talbot and Branson Motors. For now they will be selling secondhand cars but expect to eventually branch out with new cars and possibly production. Tom will alternate between working at the shop and helping Mary run the estate, while Henry will man the shop full-time. He fears Mary will not approve but she is delighted. She also has some news, that they are expecting a baby. She doesn't want to announce it until after Edith's wedding so as not to steal her thunder.
Christmas is celebrated and guests begin arriving at Downton for the wedding. Atticus and Rose come from America but without their three-month-old daughter, Victoria Rachel Cora. Their nanny felt the trip would be too dangerous for the infant, what with all the diseases she might catch on board ship and in England. Rose shows pictures of the baby to the servants and is pleased that Anna is pregnant. The Bates baby is due in only a few days.
Realizing how upset Robert is about Cora spending so much time at the hospital, Rose takes him to listen in on a meeting. Cora is answering questions from the villagers regarding the changes to their care and Robert realizes what a good job she is doing. Rose advises Robert to let Cora continue in her work; otherwise they will grow apart.
Lord Merton thinks his diagnosis might have been wrong, as he feels very well when he should be fading away. Dr. Clarkson agrees to repeat the tests and diagnoses Merton with regular anemia, which can be treated with iron tablets and a special diet.
Edith and Robert share a few tender moments before the ceremony. Laura Edmunds comes to the wedding. She and Tom exchange a few smiles and seem to be hitting it off very well. Anna is obviously uncomfortable and complains of feeling hot. The ceremony begins and this time the groom stays put.
Back at Downton, Carson tries to pour champagne but spills it. Spotting Barrow in the crowd, Robert suggests that he be appointed as Downton's new butler since he knows the routine. Carson somewhat reluctantly agrees and Barrow accepts the offer. He will start as soon as he works out his notice.
After taking some medicine for an upset stomach, Anna goes upstairs to return the hair dryer to Mary's room. Her water breaks and Mary insists she get into bed at once, even undressing her and loaning a nightgown. Dr. Clarkson and Bates are sent for. Carson is horrified that a servant is in Lady Mary's bed giving birth but there is no time to move her. The baby is a boy. Anna tells Mary she wants to continue working after her recovery. Mary says she can leave the baby in the nursery and after that, "we'll see."
Laura catches the bridal bouquet and the newlyweds depart. In a few days, Cora is taking Marigold to Brancaster Castle so she will be there when Edith and Bertie return from their honeymoon.
Robert compliments Cora on the wonderful job she is doing at the hospital. Violet and Cora mend their fences after all the arguing of the past year.
In the servants hall, champagne is flowing. Mr. Mason hints to Mrs. Patmore that his feelings for her are more than friendship. Baxter does the same with Molesley, who has come back to help out for this special occasion. At the stroke of twelve, Mrs. Hughes begins singing "Auld Lang Syne." The others join her.