World War I is raging on as we return to Downton Abbey for season two.
Matthew is in the trenches on the front lines, while his mother works from home to build a hospital for wounded soldiers.
Only very few men are left in the household, those who are physically unable to serve and those Violet had "overlooked" as a special favor to spare them various injury.
Matthew has been coming home to London, but not to Downton Abbey, and has taken a fiance. He brings her to the house for a benefit concert to meet the family. Lady Mary is home at the same time. They make amends.
Lord Grantham admits how much he has missed Matthew.
Lady Sybil wants to help with the war effort, and Isobel suggests nursing. Sybil then learns simple household skills from the staff in secret. Lady Cora discovers the secret, is proud and supports her daughters decision.
Lady Edith learns to drive the car so that she can act as the cheauffer should Branson be called to duty.
Mr. Bates believes he will finally get a divorce from his wife and asks Anna to marry. However his wife learned of the death at Downton Abbey that was covered up by Lady Cora, Lady Mary and Anna, and she threatened to expose them should he not leave service.
Violet calls in a favor with an Army doctor to request some of the men at the abbey be looked over for active duty due to medical reasons. Isobel learns of this and demands they all be treated the same.
A new servant, Ethel, is toyed with by Miss O'Brien because of her constant talk of dreams and leaving the household.
Matthew finds Thomas in the trenches after he visits Downton Abbey. Thomas, a swaggering man at home, is not faring well on the front.
Lord Grantham is only in the war in an honorary capacity, and he feels quite inadequate.
When Lady Sybil joins the hospital as a nurse in training, Branson declares his love and asks her to bet on him and his certainty that WWI will offer him an opportunity to make something of himself that will make him a worthy suitor in the eyes of her family.
Lady Mary meets Matthew at the train and gives him her good luck charm, and then prays for him to come home safely before going to bed.
Thomas intentionally gets himself wounded so that he can go be sent home from the front lines. His wound is bad enough that he will not be sent back to the lines.
William is called up to serve, and asks Daisy to have a photo taken so he can take it with him. When he comes back during training she is beside herself with worry that she has given him the wrong idea that they are a couple.
Edith takes a job driving a tractor at a neighboring farm.
Mr. Lang, Robert's new Valet arrives and he has a bad case of shell shock.
Mr. Mosley pursues Anna, but is turned down. Anna cannot dismiss her love of John Bates.
Sir Richard proposes marriage to Mary, and she decides to accept, given Matthew's circumstances with Lavinia.
The decision is made to to convert Downton Abbey into a convalescence home.