The dramatic promo features the introduction of Oscar-winning American actress Shirley MacLaine as Martha Levinson, mother of Cora (Elizabeth McGovern).
Set to a choral version of Lou Reed's 'Perfect Day', the video clip also offers a glimpse of Bates (Brendan Coyle) in prison and romantic scenes for Lady Mary (Michelle Dockery) and Matthew Crawley (Dan Stevens).
MacLaine previously promised that viewers can expect "a little sparring" between her character and the Dowager Countess (Maggie Smith).
"We do a little sparring but it's more sophisticated and adult," said the veteran star. "Martha is not just a crass, cranky American coming in there to call a spade a spade. She's very smart and sensitive."
Downton Abbey will return to ITV1 on Sunday, September 16 at 9pm.
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> Shirley MacLaine, Maggie Smith in new Downton Abbey trailers: Watch