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

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.

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.

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.

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.

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.

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.

The Great War unsettles life at Downton and surprising news about Matthew rocks the family. New maid Ethel irritates O'Brien - and Bates returns with devastating news for Anna.

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?

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.

Robert receives some shocking news from the front. Daisy's relationship with William moves faster than she would like. Vera threatens to expose old secrets.

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.

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.

With the wedding approaching there is excitement in the air, but will Branson's plans rattle everyone? A decisive Anna forces Bates to think about their future.

Cora’s mother sweeps into Downton for Matthew and Mary’s wedding, but with the couple’s relationship under strain will they even make it to the altar? New footman Alfred strives to meet Carson’s high standards, under the watchful eye of his aunt O’Brien. Robert’s shocking news brings financial worries to the fore, on an unprecedented scale. Might he lose Downton itself and all it stands for?

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.

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.

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.

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.