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.

Lady Edith shocks her family when she tells them that she's going to help a local farmer, who finds himself without farmhands, by driving the man's tractor. Edith proves to be quite up to the task but she gets more than she bargained for when the married farmer kisses her and she welcomes his advances. Robert Cawley's new valet, Henry Lang, makes something of a fiasco while serving at dinner. He is shell-shocked, though few recognize it.

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.

Everyone is shocked by the news that both Matthew and William have been seriously injured at the front. While Matthew is on his way to the family home for treatment, they are told that William cannot convalesce at the Abbey as it is for officers only. Lady Violet, the Dowager Duchess, won't stand for it, however, and uses all of her influence to have William brought to the Abbey as well. She succeeds but William will not recover from his wounds and asks Daisy to marry him right away.

An unrecognizable burn victim turns up at the convalescent home claiming to be Mary's presumed drowned cousin Patrick, Carlisle plans to lure Carson from Downton, and Bates' wife reneges on her divorce agreement.

Ethel confronts her baby's grandparents, Bates thinks he might have played a role in his wife's death, Branson and Sybil elope, and Carlyle tries to recruit Anna to spy on Mary.