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.

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.

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.

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?

Carlisle threatens to ruin Mary if she jilts him. A major comes to stay - but is he really who he claims to be? Bates learns that Vera has succeeded in scuppering the divorce.

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.

An extravagant house party at the Abbey gives the Crawleys a chance to reconnect with old friends. But some guests prove more welcome than others, and along with the celebrations come skulduggery and heartache.

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.

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.

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.

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.

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.

The estate's future is hanging in the balance and Mary is hoping to receive a bailout from grandmother Martha. Violet also attempts to help her make sure that Downton puts on a bigger show than ever before with a grand party for friends and neighbours. Mrs Hughes gets some news that worries her. O'Brien's attempts to boost Alfred's progress are met with disapproval from Thomas.

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.

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.

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.

A birthday party is planned for Robert, but Rose's surprise contribution to the event ruffles feathers above and below stairs. A new farming venture on the Downton estate comes with dramatic repercussions for Mary, and Edith receives more unwelcome news.

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.

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.

How long can Sybil and Branson keep their secret? Carlisle puts Anna in a difficult position, Bates is left reeling from the news about Vera, and Thomas embarks on a new scheme.

Tempers are left on edge after a kind gesture by Isobel backfires. Mary attempts to fight Branson's corner after his decisions are put under scrutiny. Robert and Cora's relationship feels the strain and Violet attempts to make them see things differently. Some extreme measures are taken by Bates.

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.

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.