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?