Cora's pregnancy throws the inheritance issue into doubt. Matthew must wait for an answer to his wedding proposal. O'Brien discovers more compromising information about Bates. Thomas leaves.

Carson is finding it tough maintaining standards in the house, and the suicide of a young officer prompts Isobel to suggest converting Downton Abbey into a convalescent hospital.

After Downton is turned into a convalescent home for wounded officers, Matthew brings a general to visit, but Branson has a surprise in store. And is Lavinia hiding something?

There's excitement in the house and village as the annual cricket match approaches, and the event brings out Robert's competitive side. Violet's great-niece Rose shows up but a trip to London reveals there is more to her than meets the eye. Matthew and Mary look like they are keeping secrets from each other. Thomas finds out that his future lies in Carson's hands.

Amid the fallout from the eventful house party, Mary faces a pressing question about her future. Carson reveals surprisingly intimate details of his former life, and a trip to the bright lights of London sees Rose put the reputation of the Crawleys in jeopardy.

Cora's playboy brother has got himself into a spot of bother and Robert has to make a trip to America to bail him out. Blake and Mary are forced to put aside their differences to deal with a new farming venture on the estate. When Violet is taken ill, help comes from an unlikely quarter. In spite of Mrs Hughes, Mrs Patmore and Carson's attempts to keep the peace, romantic tensions below stairs cause problems.

Rosamund comes up with a plan to help Edith deal with her problem, but Violet may be about to see right through it. Isobel is the object of someone's attention, while Mary asks Gillingham for a favour. Rose is frustrated when things do not go her way and Alfred realises too late that he may have made a mistake. Just as Bates and Anna seem to be getting over the worst, some unexpected news shakes her up.

It's summer and as part of Rose's 'coming out' she is to be presented at Buckingham Palace. The family are in London, preparing Grantham House for the busy social program.

Sarah Bunting continues to cause waves above stairs, but this time she may have gone too far. On returning to Downton, Thomas suffers an inexplicable illness and Baxter suspects there’s more to it than he’s letting on. Violet reveals to Isobel the surprising truth of her past with Prince Kuragin. Mary comes to a decision concerning Lord Gillingham, but things don’t go quite as planned. When Rose’s father returns to Downton, he breaks news that will shock the whole family.

Simon Bricker returns to Downton to discuss the painting with Cora. Branson makes a difficult decision about Sarah Bunting. Rose encounters a handsome stranger. Determined to stop Isobel making the wrong decision about Lord Merton, Violet enlists the help of Doctor Clarkson. Charles Blake surprises Mary with a cunning plan to help her get exactly what she wants. Mrs Patmore seeks Carson's advice on a financial matter. Inspector Vyner returns with some ominous words of warning for Anna.

Rosamund shows up at Downton following Edith's surprise departure. Rose is pleased to introduce Atticus and his parents to everyone. Anna and Bates think about a fresh start, now that that their problems seem to be behind them. Molesley is worried after Daisy becoming disillusioned with her studies. Mary and Blake seize a chance to send Gillingham a strong message.

It is now 1925, when secrets and rifts threaten the unity of the family, while those below stairs are faced with social changes.

Lady Mary's meddling gets Mr Carson into trouble with Mrs Hughes. Cora and Violet lock horns over the hospital takeover plans. Robert has a tough decision to make.

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.

The Crawleys watch Henry compete in a motor racing event, an occasion that leaves Mary reeling. Violet hatches a plan which surprises the family and delights Miss Denker, and learns more about Amelia's intentions in befriending Isobel. Molesley and Daisy rise to the challenges of examination day, Andy's secret is brought to light, Thomas feels isolated, and Mrs Patmore and Mrs Hughes teach Carson a lesson.

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.

Mary endeavours to build bridges with her sister while Edith’s secret continues to pose a threat, despite having nothing left to lose. As Henry settles into the role of husband and stepfather, finding his place at Downton proves more difficult. Below stairs, Carson faces some personal challenges, which prove that even he is not invulnerable to change.