The family and staff of Downton are shocked when they find that the heir to the title and fiancé of the Earl's daughter Mary perished on the Titanic, and the Earl hires a crippled army comrade as valet.

The new legal heirs to Downton, lawyer Matthew Crawley and his nurse mother Isobel are invited to live on the estate, but there is resentment of them as interlopers from both up and downstairs as interlopers.

Gwen's ambitions to leave service to become a secretary is discouraged, Bates takes painful steps to overcome his limp, and a dashing Turkish diplomat visiting Downton seems to work his charms on everyone - especially Mary.

Mrs. Hughes is reunited with an old beau, now a widower proposing marriage, and the Countess hires Matthew Crawley to see if the will can be broken and disagrees with his mother on a diagnosis.

Bates sees Thomas stealing a bottle of wine, the footman tries to frame him for petty theft, and Mrs. Crawley tries to convince the Dowager Countess to surrender her annual entitlement prize for best bloom in the village.

O'Brien and Thomas continue their efforts to frame Bates, Mary falls in love with Matthew, and Sybil is injured in a political disturbance and Branson is blamed.

Mary finds it was Edith who let the ambassador know about Pamuk's death, Cora announces her pregnancy, and Thomas and O'Brien hatch new slanders against Bates as War clouds loom.

After Bates' mother dies, he hopes his inheritance will buy him a divorce and allow him to marry Anna, Matthew announces his engagement to Lavinia Swire, and Sybil gets involved in the war effort.

April 1917. With John still absent, Isobel's butler Molesley makes a play for Anna but is rejected. Robert gets a new valet, shell-shocked ex-soldier Henry Lang, whilst William goes off to war. Edith learns to drive a tractor extremely well, and nearly succumbs to a kiss from the married farmer Mr. Drake. Sybil and Thomas work in the cottage hospital, where the latter begins to learn some humanity. At Isobel's suggestion - and to Violet's dismay - Downton Abbey is turned into a convalescent ward to ease the hospital's bed shortage. Mary invites middle-aged newspaper tycoon, and prospective beau, Sir Richard Carlisle to a dinner party, also attended by the Crawleys and Lavinia. Suspicious of Carlisle, Violet invites her daughter and sister to the Earl, Lady Rosamund, who is intrigued by the fact that Carlisle and Lavinia already seem well-acquainted. Carson, despite being taken ill whilst serving dinner, is still perceptive enough to suggest to Mary that Matthew is really the man for her.

Downton is turned into a convalescent hospital for the war wounded and through circumstances Thomas is given authority in its operation as Anna and Bates are briefly reunited and Branson plots against a heroic general dining at Downton.

Matthew and William are missing in France, the mounting tensions between Cora and Isobel result in Isobel's volunteering for France, Bates returns to Downton, and the servants open a soup kitchen for unemployed veterans.

August 1918: Deserted by the baby's father, Ethel has been installed with her child in a cottage on the estate by a sympathetic Mrs. Hughes, who brings her food. Jane, a war widow, has taken Ethel's place as a maid. Vera Bates returns, having spent John's money but with no intention of sticking to their arrangement and planning to make money by selling the story of Lady Mary's indiscretion to Carlisle's newspaper. Tipped off by Anna, Mary goes to see him and explains all, thus scotching Vera's plan as the newspaper owner threatens her with libel action. Having returned to the war, both Matthew and William sustain severe injuries at the Battle of Amiens, fatally in the case of William, who marries Daisy. Mary is glad to become a hospital auxiliary to nurse Matthew, though his spinal damage will, in all probability, leave him paralysed from the waist down and impotent.

Things go badly amiss at Downton Abbey. Robert and Cora are not speaking. The servants are shunning Matthew's mother, Isobel. And Matthew and Robert have fallen out. Bates takes a gamble.

Downton Abbey opens its doors to the public for charity, Barrow's actions are misconstrued, Mary and Henry's romance blossoms, and tensions between Cora and Violet reach a dramatic climax.

August 1918: Deserted by the baby's father, Ethel has been installed with her child in a cottage on the estate by a sympathetic Mrs. Hughes, who brings her food. Jane, a war widow, has taken Ethel's place as a maid. Vera Bates returns, having spent John's money but with no intention of sticking to their arrangement and planning to make money by selling the story of Lady Mary's indiscretion to Carlisle's newspaper. Tipped off by Anna, Mary goes to see him and explains all, thus scotching Vera's plan as the newspaper owner threatens her with libel action. Having returned to the war, both Matthew and William sustain severe injuries at the Battle of Amiens, fatally in the case of William, who marries Daisy. Mary is glad to become a hospital auxiliary to nurse Matthew, though his spinal damage will, in all probability, leave him paralysed from the waist down and impotent.

Mary finds it was Edith who let the ambassador know about Pamuk's death, Cora announces her pregnancy, and Thomas and O'Brien hatch new slanders against Bates as War clouds loom.

Mrs. Hughes is reunited with an old beau, now a widower proposing marriage, and the Countess hires Matthew Crawley to see if the will can be broken and disagrees with his mother on a diagnosis.

Downton is turned into a convalescent hospital for the war wounded and through circumstances Thomas is given authority in its operation as Anna and Bates are briefly reunited and Branson plots against a heroic general dining at Downton.

April 1917. With John still absent, Isobel's butler Molesley makes a play for Anna but is rejected. Robert gets a new valet, shell-shocked ex-soldier Henry Lang, whilst William goes off to war. Edith learns to drive a tractor extremely well, and nearly succumbs to a kiss from the married farmer Mr. Drake. Sybil and Thomas work in the cottage hospital, where the latter begins to learn some humanity. At Isobel's suggestion - and to Violet's dismay - Downton Abbey is turned into a convalescent ward to ease the hospital's bed shortage. Mary invites middle-aged newspaper tycoon, and prospective beau, Sir Richard Carlisle to a dinner party, also attended by the Crawleys and Lavinia. Suspicious of Carlisle, Violet invites her daughter and sister to the Earl, Lady Rosamund, who is intrigued by the fact that Carlisle and Lavinia already seem well-acquainted. Carson, despite being taken ill whilst serving dinner, is still perceptive enough to suggest to Mary that Matthew is really the man for her.

Matthew and William are missing in France, the mounting tensions between Cora and Isobel result in Isobel's volunteering for France, Bates returns to Downton, and the servants open a soup kitchen for unemployed veterans.

The family and staff of Downton are shocked when they find that the heir to the title and fiancé of the Earl's daughter Mary perished on the Titanic, and the Earl hires a crippled army comrade as valet.

The new legal heirs to Downton, lawyer Matthew Crawley and his nurse mother Isobel are invited to live on the estate, but there is resentment of them as interlopers from both up and downstairs as interlopers.

Gwen's ambitions to leave service to become a secretary is discouraged, Bates takes painful steps to overcome his limp, and a dashing Turkish diplomat visiting Downton seems to work his charms on everyone - especially Mary.

Bates sees Thomas stealing a bottle of wine, the footman tries to frame him for petty theft, and Mrs. Crawley tries to convince the Dowager Countess to surrender her annual entitlement prize for best bloom in the village.