The runaway UK hit returns! Last season closed with the reluctant heir to Downton, Matthew Crawley, recovered from his war wounds and ready to tie the knot with the eldest of Lord and Lady Grantham's daughters, Lady Mary. Meanwhile, Mary's youngest sister, Sybil, has eloped to Ireland with the political-minded chauffeur, Branson, and is expecting a child.

A tantalizing glimpse ahead: Downton's impeccable butler, Carson, breaks in a new footman, who happens to be the nephew of the scheming lady's maid O'Brien. 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.

In this changing landscape nothing is assured, and could it be that even the war-weary Crawleys must fight a new battle to safeguard their beloved Downton?

Much has changed in the year between the Christmas special and now. But as we enter the Roaring Twenties, how will people, and indeed the great house itself, adapt to the new post-war world?