The Great War is over and a long-awaited engagement is on, but all is not tranquil at Downton Abbey as wrenching social changes, romantic intrigues, and personal crises grip the majestic English country estate for a third thrilling season. Downton's impeccable butler, Carson (Jim Carter), breaks in a new footman, who happens to be the nephew of the scheming lady's maid O'Brien (Siobhan Finneran). Following Matthew and Mary's engagement, Robert sticks to his duty to maintain Downton more firmly than ever - even as other great houses are crippled psychologically and financially in the wake of World War I.