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.

With the house recovering from the night’s dramatic events, Robert is faced with a very difficult decision. As Daisy continues to struggle with her studies, Mrs Patmore has an idea which might solve everything. Thomas has it in for Baxter. As Rose tries to convince Robert of the virtues of a wireless at Downton, Lord Merton continues his hot pursuit of Isobel. When Mary puts her reputation on the line, Anna is made a reluctant accomplice.

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.

It's a good day as Anna's patience is rewarded and Edith gets some admiration from an unexpected quarter. Matthew refuses to back down over the estate management. Branson's plan for the christening causes some consternation, as does the sudden arrival of his brother.

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.

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.

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?

Branson's political views manage to get him into trouble while Sybil's loyalty is tested to the limit. Ethel finds herself being torn between head and heart as she makes a decision about her son's future. Anna is upset by Bates's silence and wonders what could be the cause. Carson looks for a new footman and a good-looking candidate called Jimmy creates interest below stairs.

Relations between Robert and Cora continue to be strained. Blake's scheming starts to come to fruition when Mary is unexpectedly pitted against her love rival. Edith receives some terrible news and decides to take drastic action. Following a mysterious tip off, Baxter becomes embroiled in the investigation of Green's death. Thomas' condition deteriorates, prompting him to finally reveal the truth to Baxter. Love is in the air for more than one member of the Crawley family.

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.

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.

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.

Mary's secret assignation is very nearly blown, but Violet's quick thinking saves the day. Robert is left red faced and furious when things do not go as planned. The events surrounding Green's death come under scrutiny once again. Mrs Patmore is devastated when old wounds are reopened but Carson is unsympathetic. Branson receives an interesting proposition concerning the future of the Downton estate. A figure from Violet's distant past suggests she has buried secrets of her own.

After the death of the heir, Violet wishes that Robert's daughter Mary could inherit Downton Abbey.

Tensions flare between Isobel and Cora. Ethel's flirtation with Major Bryant lands her in hot water. There is worrying news about Matthew. Branson declares his feelings for Sybil.

Cora's tries to set up Mary with Evelyn Napier, who falls for his friend instead, with significant consequences for the household. Bates takes action to help cure his limp.

Edith's wedding day arrives but will her enthusiasm be able to convince the family that Strallan's age doesn't really matter. Mrs Hughes awaits her results. Anna manages to make a breakthrough as she tries to help Bates. Mary decides to take matters into her own hands to secure the estate's future.

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

Change is in the air as an exciting opportunity for Alfred creates tension between Ivy and Daisy. Isobel appeals to Violet's charitable nature, but it does not come without a fight, and Branson considers a new future for himself and baby Sybbie.

Matthew Crawley and his mother Isobel arrive at Downton, and have difficulty settling in. Carson is mortified when confronted by his past. Violet attempts to promote a match between Matthew and Mary. Isobel is elected to serve on the hospital board.

Sybil puts herself in danger when a fight breaks out. Sybil's sisters notice Matthew's feelings for her. Mary is surprised by a marriage proposal. Bates clears his name over the missing wine but resigns rather than name the real culprit.

An exciting offer for Edith divides opinion in the house. Isobel ends up throwing Ethel a lifeline. Ivy is attracting plenty of attention below stairs. Anna’s perseverance finally pays off for her.

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.

Preparations are under way for Rose's wedding, but family tensions on both sides threaten to derail proceedings. Edith's arrangement with Marigold is happily working out, but how long can she and Cora conceal the truth from Robert? Denker reveals an unexpected side to her personality, which causes trouble for more than one of the servants. With the war memorial due to be unveiled, Mrs Patmore is still upset, but Robert has something up his sleeve. Branson comes to a heart-wrenching decision, and the storm clouds that have been gathering over Anna and Bates finally burst.