The Crawleys discuss Edith's decision to enroll Marigold in a London school and to move to London. Cora and Robert are hesitant about it, but Edith is resigned to spinsterdom.
Mary talks to Henry privately, noticing he is down. He explains that he no longer gets joy out of racing.
Thomas thanks Andy, Anna, and Baxter for saving him. Anna advises him to use his time before having to leave Downton to figure out what brought him to the point of suicide.
Isobel and Violet discuss the fact that Larry and Amelia Grey suddenly canceled on their planned meeting and that she has been unable to get ahold of Lord Merton. Violet encourages her to do some snooping to figure out what is going on.
Henry plans to drive Edith up to London, as they both have business to take care of there.
Andy flirts with Daisy and Mrs. Patmore makes a comment to Daisy about it. Daisy insists that she could do better than Andy, showing no interest in him.
At dinner, the Crawleys discuss visiting Violet. Cora explains that she can't because she has a hospital meeting. Robert is annoyed. Carson's hands shake uncontrollably, causing him to spill wine. The whole family is alarmed while Carson is profusely apologetic.
Andy seeks Mrs. Patmore's advice about Daisy. She encourages him to do a bit of wooing.
Thomas gets a job and tells Anna and Mr. Carson. Mr. Molesley plans to go into town and Baxter tells him she'll go with him.
Edith arrives at the Dowager's house to talk to Spratt about expanding his advice column to a full page. Denker listens in secretly.
Molesley and Baxter walk through town and Mr. Dawes approaches Molesley. He tells Molesley that one of the teachers is retiring. He offers Molesley the man's cottage and to take over some of his duties. Molesley is shocked but happy. Baxter encourages him to think about it and make the right choice.
Denker tries to wrangle the truth about Edith's visit out of Spratt. Spratt refuses to give anything up.
Carson's hand shaking alarms Mrs. Hughes. He tries to keep it secret from her, refusing to acknowledge it. They are interrupted by Molesley, who tells Carson about being offered the additional classes at the school. He asks for advice.
Mary and Robert visit Violet. They discuss Edith and Bertie. Violet gives Mary an idea about the two of them. They confess that Cora has a hospital meeting and couldn't make it. Violet points out that it no longer bothers her but seems to bother Robert recently.
Isobel visits Lord Merton. He confesses that he was in London to see doctors and that he's found out he has penicious anemia, a terminal illness. Isobel is saddened by this news.
Edith and Henry arrive in London. Edith sees that she has been invited to dinner at the Ritz with Aunt Rosamund. Henry confesses to Edith that he is thinking of giving up racing. Edith encourages him to find something to do to replace racing.
Barrow gives his notice to Mr. Carson and the rest of the servants. Anna receives a hair dryer that she got at Lady Mary's request.
Edith meets Aunt Rosamund at the Ritz, where she finds Bertie waiting. Edith is shocked and Rosamund leaves the two alone to have dinner. Bertie reveals that Mary set it all up. Bertie explains that he wants her back. Edith insists that nothing has changed, but Bertie proposes to Edith again. She asks whether they'll have to tell his mother about Marigold. Bertie says he prefers not to tell her, because in that case they'd have to break with her.
Thomas and Baxter chat. Barrow explains that he wants to be a new person at his new position. He encourages Baxter to let go of the past and forget about Coyle. Baxter admits he may be right.
Edith calls the house and tells Robert that she and Bertie are engaged. Robert tells Cora, and tells her that they are going with Bertie and Edith to Brancaster to announce it to Bertie's mother and to meet her.
Isobel confides in Violet that she is very sad about Lord Merton's diagnosis. Violet points out that she's in love with him. Isobel wonders why she turned him down.
Baxter confides in Molesley that she's decided not to go see Coyle. She bids farewell to Thomas. Mr. Bates also says farewell to Barrow as friends, rather than enemies. Robert and Cora say goodbye to Thomas, with Thomas thanking them and Robert wishing him luck. Robert, Cora, Baxter, and Bates head off to Brancaster.
Daisy complains that she is a frump and wants to change her hair. Mrs. Patmore criticizes Daisy for rejecting Andy, and for rejecting any man that has feelings for her until they stop having feelings for her.
Cora, Robert, Edith, and Bertie go to Brancaster Castle and meet with Bertie's mother.
At dinner at Downton, Mary, Tom, and Henry discuss Henry's decision to stop racing. Carson again experiences the shakes and Mary sends him downstairs, worried. Downstairs, Carson confesses to Mrs. Hughes that he knows what he has -- a hereditary condition that both his father and grandfather had, which they called "the palsy," and which finished their careers as butlers. Mary visits Carson downstairs and assures him that he is dear to her and that if there are changes to be made, they'll make them.
Henry and Tom discuss what Henry will do with his life now that he is no longer racing. Henry encourages Tom to share any ideas with him.
After dinner, Mrs. Pelham reveals herself to be exceedingly moral, making Bertie and the Crawleys nervous about Edith's secret. She criticizes Bertie's deceased cousin fo his immoral life, angering Bertie.
Lord Merton and Isobel visit Dr. Clarkson and he confirms that Merton does indeed have pernicious anemia. Isobel assures Merton she won't leave his side. Amelia Grey finds them, having tracked them down, and has the driver usher Lord Merton away while she warns Isobel off, telling Isobel to stay away from them.
Robert encourages Edith to move forward and be happy with Bertie, when Edith expresses trepidation about whether she's doing the right thing.
All of the servants wish an emotional Barrow a warm farewell. Mary brings the children downstairs to say goodbye to him. He departs.
Edith visits Mrs. Pelham privately and confesses the truth about Marigold to her.
Thomas settles into his new position with the Marks. He is dissatisfied to discover there are only two other servants there.
Daisy visits Mr. Mason's farm and sees Andy there working on the farm. Andy reacts coolly to her, finally piquing Daisy's interest in him. Mr. Mason tells Daisy she could do worse than Andy and reiterates his invitation for Daisy to move into the farm with him.
Bertie confronts his mother about Edith's reveal. She tries to convince him to break up with Edith, calling her "damaged goods," but he refuses to consider it.
Isobel turns up at Lord Merton's house. Amelia refuses to allow her entry into the house to see Lord Merton, insisting that he wants to spend his remaining time with his family.
Tom and Henry plan on setting up a secret enterprise, just the two of them, without the family's assistance.
Isobel visits with Violet. Violet encourages her to try force to push past the servants and go up to see Lord Merton.
Molesley gives his notice to Carson but offers to stay on for special events or big parties. Carson is distracted by his worsening condition and rude to Molesley. Mrs. Hughes chastises him for being rude to Molesley and keeping secret his condition.
At the dinner at Brancaster Castle, Bertie prepares to announce his engagement to Edith. At Robert's urging, Mrs. Pelham stands up and makes the announcement herself, indicating her approval of the match, to Edith's relief. Later that night, Mrs. Pelham confirms that she appreciates Edith's honesty.
Violet and Isobel show up at Lord Merton's estate. Amelia and Larry try to prevent them from seeing Lord Merton. Violet accuses them of trying to keep Isobel away from Merton now that he is going to die. Lord Merton hears her voice and comes downstairs. Isobel tells him to pack his things and come with her, and announces her intention to marry him as soon as possible. Merton joyfully accepts and shuts down the arguments of Larry and Amelia, telling them they can take the house.
Bertie, Edith, Cora, and Robert return home. Edith reports that they are thinking about a New Year's Eve wedding. Edith asks Mary about her interference. Mary tells Edith that they are blood and they should try to do a little bit in the future.
Daisy tries to thank Andy for his hard work at the farm. Andy coldly tells her that he did it for Mr. Mason and points out that he knows Daisy doesn't like him. He leaves and Mrs. Patmore chides Daisy for starting to like Andy now that he's gone off her. Molesley tells Baxter that he has accepted the teaching position and will be leaving. Baxter assures him that they won't lose touch.
We flash forward three months to December 29th, 1925, two days before Edith's wedding. Downton is in full wedding-prep mode.
Rose and Atticus arrive and tell the family about their baby daughter. Rose runs downstairs to show the servants pictures of her daughter. She spots a very pregnant Anna, who confirms she is due in about ten days. Rose asks after Barrow and the other servants admit that he hates his job.
Denker tells Spratt that she knows his secret.
At dinner, Isobel tells everyone that Lord Merton is resting at home because of his illness, but that he is the picture of health. She thanks Rose for the wedding gift she sent them. Cora reports that she has a hospital meeting the next day. Robert criticizes Cora for missing the flower appointment the next day. Rosamund shoots him down.
Mary and Robert go downstairs to talk to Carson. Carson explains his condition to them and offers his resignation since he can no longer perform his duties.
Isobel spots Lord Merton at the hospital, wondering what he's doing there. He admits that he doesn't feel very ill so he's gone to Dr. Clarkson to run more tests.
After Robert continuously complains about Cora spending so much time at the hospital, Rose takes him to see Cora in action at the hospital meeting, answering the villagers' questions and reassuring them about the hospital changes. Robert is proud of her. Rose encourages Robert not to ruin his marriage by making Cora choose between him and the hospital.
Henry and Tom take Mary to see their new venture, a car garage and used car shop that they plan on building into a new car dealership and factory. Mary is ecstatic and proud of them. She also confides in Henry that she is pregnant but asks him not to say anything to anyone, so as to not steal Edith's thunder.
Daisy sneaks upstairs and borrows Lady Mary's hair dryer, messily cutting her own hair.
Denker tells Violet about Spratt's writing job and shows Violet his column, assuming Violet will give Spratt his nervous. Violet clarifies that she won't be giving him notice and laughs hysterically at the column.
Daisy tells Anna and Mrs. Patmore that she isn't going to the wedding. Anna wonders why Daisy is wearing her cap pulled down and Mrs. Patmore tells her to take it off. Daisy reluctantly removes the cap. Andy laughs at her and Daisy runs away, embarrassed. Mrs. Patmore chastises Andy for laughing and for being blind to Daisy's feelings for him.
Edith and the other members of the family prepare for the wedding.
Anna fixes Daisy's hair before the wedding. Andy talks to Daisy and tells her that he'd like for them to be on the same page about their feelings for one another. He takes a cut lock of her hair and Daisy smiles.
At the wedding, Tom chats with Laura Edmunds, Edith's editor. Dr. Clarkson reports to Isobel and Lord Merton that Merton does have anemia, but not the deadly type.
Robert and Edith chat right before he walks her down the aisle. Robert tells Edith how proud he is of her.
Edith and Bertie marry.
At the reception, Robert tells Cora that he saw her at the hospital and he tells her he was proud of her and confirms he wouldn't ask her to give it up.
Daisy tells Andy that she has decided to move into the farm and that she has decided other things that she won't tell him about yet. They both smile.
Carson has a breakdown when he is unable to pour during the reception. Barrow jumps in and offers to assist. Robert offers a solution: Carson will retire from active duty and Barrow will return to Downton as butler, with Carson overseeing everything. Barrow accepts and Carson sadly agrees.
While in Lady Mary's room with her, Anna suddenly goes into labor. Mary snaps into action, helping Anna undress and prepare. Henry rushes to call Bates upstairs.
Violet confronts Spratt about his column, telling him that she'll come to him from advice from now on. This annoys Denker and makes Spratt smug.
Daisy confirms to Mr. Mason that she'll come to live at the farm. Mr. Mason tells Mrs. Patmore that he hopes he'll be seeing a lot more of her as well, making Mrs. Patmore bashful and Daisy smile.
Shrimpy delivers the speeches at the wedding. Everyone toasts Edith and Bertie and then sees them off as they leave for their honeymoon. Before they leave, Edith tosses her bouquet and Laura Edmunds catches it, exchanging a look with Tom.
Robert tells Carson that he and the family are very grateful to him. Carson becomes emotional.
Anna and Bates sit in Mary's bed with their son. Anna tells Mary she wishes to continue working, and Mary tells her that the baby can be in the nursery, to be joined by her own child soon enough.
Violet and Cora reconcile, with Violet telling Cora that it is her village and her hospital now, and that Cora runs it very well.
The clock strikes midnight and everyone wishes one another a happy new year. All of the couples kiss. The servants sing Auld Lang Syne.