New mother Mary is finding it hard to come to terms with Matthew's shocking death. Robert and Violet fall out over how to handle the situation. Jimmy takes an interest in Ivy, while Carson receives an unwelcome reminder from his past.

The story moves on to 1924, when the first ever Labour government heralds a sea change that is felt throughout the nation - nowhere more so than at Downton. A suggested plan for a war memorial unexpectedly pits Carson against Robert and Mrs Hughes. Young Jimmy the footman is the object of some unwanted female attention. Thomas gives Baxter an ultimatum. Branson's growing friendship with someone Robert considers quite unsuitable causes concern. After the tragedy she has been through, Lady Mary now seems ready to find love once more. Cracks appear in Edith and Tim Drewe's special arrangement as she struggles to keep her emotions in check - something which may have disastrous consequences for the entire household.

As Tom and Sybbie settle back into life at Downton, the family and servants are surprised by the return of another old friend in unexpected circumstances.

Bertie's circumstances change suddenly, leaving Edith uncertain whether to risk telling him the truth or keep her past a secret at all costs. Mary wonders if she can ever make peace with her sister as hostilities escalate, Spratt shows some hidden talents and Molesley's first day as a teacher does not go according to plan. Mrs Patmore's bed and breakfast attracts unwanted attention, leaving her in need of the Crawleys' help.