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.

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.

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.

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.

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.

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

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.

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.

Preparations for the wedding of Mr Carson and Mrs Hughes are under way. Edith meets up with an old acquaintance. Spratt has something to hide.

Mrs Hughes finds herself the focus of speculation when she meets a former suitor who makes her question her position. Violet and Isobel clash over a medical ailment affecting Molesley. Carson is concerned there is a thief at work in the grounds.

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.

Neville Chamberlain visits Downton for dinner, and is drawn into Violet’s plan to save the hospital, with distressing consequences for everyone. Andy finds an unexpected confidante while helping Mr Mason move into Yew Tree Farm, Mary is uncertain if she has met her match, Edith meets Bertie Pelham in London, and Spratt comes to Denker’s aid. Mrs Hughes struggles to keep Carson happy, while Mary thinks secrets are being kept from her.

The house is made open to the public to raise money for the hospital, an act that divides opinions among the family and the servants. Tensions between Violet and Cora come to a head as a decision is made about the hospital takeover, Mr Dawes has a proposition for Molesley, and Baxter is thrown into turmoil by an unexpected letter. Carson is not happy with Thomas, while Mary and Edith hope to overcome their past and find new happiness with the men in their lives.

Isobel finds herself at odds with Violet. Mary is introduced to a potential suitor but wants to be with Matthew. Anna works out who stole a valuable snuff box. O'Brien plans a way for Edith to get even with Mary.

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.

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.

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.

Mary starts to get over the grief she is feeling, and takes an interest in the running of the estate. Lady Rose MacClare, Lady Flintshire's daughter, ends up in a predicament at a tea dance in York. Hughes attempts to convince Carson to heal an old wound.

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?