Tim Drewe guesses the parentage of Marigold, Mary receives another proposal from Tony, Violet plays matchmaker, Thomas continues to press Baxter for information with blackmail, and a flash fire threatens the mansion.
James leaves Downton, Mary has a weekend rendezvous with Gillingham, Carson and the Earl disagree for the site of the War memorial, a wireless becomes part of Downton life, and Edith becomes Marigold's godmother.
Mary wakes up in bed with Tony Gillingham after their tryst and returns to Downton, where she learns that a building firm want to buy land for a housing estate, to which Robert objects. Violet discovers from her butler Spratt about Mary and Tony but covers for her before summoning her for an explanation.
The Countess confesses her past with russian Prince Kuragin, Lord Merton proposes to Isobel, Rose's parents are divorcing, Lord Grantham becomes jealous of Simon, and Lady Mary tells Gillingham she won't marry him.
Tom ends his relationship with Sarah, Rose meets a jewish young man of Russian descent, Rosamund's visit to Marigold has consequences, Mrs. Patmore asks advice for her inheritance, and Simon Bricker expresses his love for Cora.
Violet's new maid doesn't seem to be working out, Kuragin reveals he still loves Violet. Thomas reveals he is undergoing harmful conversion therapy to Baxter.
Atticus brings his parents, Edith and her daughter are brought home by Cora, Tom decides to take his daughter to America, Baxter volunteers to testify for Bates, and Isis is dying.
Kuragin tells Violet he wants to live with her, someone tries to break up the Atticus and Rose wedding, Daisy wants to live in London, and Anna is arrested for Green's murder.
Autumn of 1924. It's grouse shooting season and Rose's father-in-law invites the Crawley family to a shooting party in Northumberland. Mary and Edith meet their new suitors.
