In the series finale, Mr. Carson faces a health issue; Thomas takes a new job; Denker informs the dowager of Spratt's magazine column; Violet helps Isobel see Lord Merton, whose family is keeping them apart; Bertie proposes; and Anna goes into labor.
Mary informs Bertie that Marigold is Edith's daughter; Mrs. Patmore's bed and breakfast faces a scandal: adulterers stayed the night; Molesley becomes a teacher; Thomas attempts suicide; and Violet helps Mary figure out her feelings for Henry.
Mary and the family attend one of Henry's motor races; Mrs. Patmore opens her bed and breakfast; Mrs. Hughes tricks Mr. Carson into doing the housework; Bertie asks Edith to marry him; and Violet gives Robert a surprise gift.
The hospital board approves the merger; Daisy tries to block the burgeoning romance between Mrs. Patmore and Mr. Mason; Henry tells Mary how he feels about her; and Mary and Tom open the house to the public in order to raise funds for the hospital.
Violet arranges for Neville Chamberlain to come to dinner at the estate, but the meal proves memorable for another reason; Thomas offers to teach Andy how to read; Edith hires a woman editor; and Mr. Carson criticizes Mrs. Hughes' culinary skills.
Violet tries to sway Robert to her position regarding the hospital; Edith fires her editor; Thomas has a job interview; Denker digs up dirt on Spratt; Daisy believes Mr. Mason should move into the former Drewe farm; and Mr. Carson and Mrs. Hughes marry.
The location of the wedding reception becomes an issue between Mr. Carson and Mrs. Hughes; Thomas seeks employment elsewhere; Mary takes Anna to see a doctor in London about her miscarriages; and Mrs. Drewe abducts Marigold.
The sixth and final season opens in April 1925 with Robert contemplating reductions to the staff; Mrs. Hughes worried about whether Mr. Carson expects them to consummate their impending marriage; and Mary being faced with blackmail. In other events, Violet and Isobel disagree on changes at the hospital.