Stewart's Diana appears uneasy at times as tensions mount with Prince Charles, portrayed by Jack Farthing.
Spencer takes place in the early 1990s when Diana decided to leave her marriage to Charles. Spencer was Diana's last name.
"There's eating and drinking, shooting and hunting, Diana knows the game. But this year, things will be profoundly different. Spencer is an imagining of what might have happened during those few fateful days," reads a synopsis.
Co-stars include Timothy Spall, Sean Harris and Sally Hawkins. Pablo Larraín is directing based off of a script by Steven Knight.
Spencer is coming to theaters on Nov. 5.
Diana and Charles were married from 1981 to 1996 and share two sons together, Prince William and Prince Harry. Diana died at the age of 36 in 1997 from a car crash.