1. It's 1924.The first Labour Government has come to power in Britain which has put the wind up Lord Grantham: "What worries me is our government is committed to the destruction of people like us and everything we stand for." Things are changing. Various folk from both upstairs and downstairs say this a lot in the first episode. Other stately homes are dropping their staff numbers as servants take up jobs with decent hours and less cutlery.
2. Now out of mourning, Lady Mary is still choosing between two eligible men and is soon considering a scandalous proposition from one of them. Smoke emerges from one of the Downton bedrooms - but possibly not hers. Among the other characters' love lives, the widowed Branson (Allen Leech) is getting closer to a socialist school teacher much to his father-in-law's displeasure while Mr and Mrs Bates' marriage is coming under greater strain.
3. Lady Edith is dearly missing her illegitimate daughter Marigold who is being raised by a local farming family. Edith has still not heard anything from the father of the child, the missing-in-Germany newspaper man Gregson. Meanwhile, the house's two babies - George and Sybbie - are now walking and talking and calling grandad funny names.
4. There are no visits from Lady Grantham's American mother-in-law (Shirley MacLaine) this season. However, Lady Grantham strikes up a potentially unsettling friendship with visiting art historian Simon Bricker (played by Richard E Grant). Another new guest star is feisty Lady Anstruther (Anna Chancellor) who really does her bit for upstairs-downstairs relations in the opening episode.
