The Duke gets short shrift but the Duchess never bores!

Rating: 7/10 (24 May 2009)

The Duchess is based on the true life story of Georgiana, Duchess of Devonshire who married William Cavendish, the 5th Duke of Devonshire in England in 1774. The facts of Georgiana's life form the basis of the film's plot. We're introduced to the Duchess when she is 17 years old; her family (including Georgiana) is excited that she is being married off to the Duke. After the marriage, she's soon disappointed that the Duke never talks to her and appears to be emotionally distant. Despite this, the Duchess becomes extremely popular in aristocratic circles and eventually involves herself in politics, campaigning for Whig candidates and supporting liberal causes.
Time passes and Georgiana has two daughters but is unable to produce a male heir. The Duke bitterly resents her for this. On a trip to Bath, the Duchess meets Lady Elizabeth Foster who is a victim of domestic violence—her husband has forbidden her to see her children again and she has been put out of their house. With nowhere to go, Georgiana takes pity on Lady Elizabeth and persuades the Duke to let her stay with them. In a move to get her children back, Lady Elizabeth sleeps with the Duke and Georgiana feels betrayed and orders her to leave. But the Duke overrules her and the three end up living together until the Duchess's death many years later.
Meanwhile, Georgiana has fallen for Charles Grey, later to become Prime Minister. She wants to make a 'deal' with the Duke, allowing her to see Charles while he continues his adulterous relationship with Lady Elizabeth. The Duke is so outraged by the Duchess's proposition that he ends up raping her. The Duchess ends up pregnant and finally produces a son. But the Duchess cannot stay away from Charles and she ends up pregnant. After a daughter, Eliza, is born, the Duke sends the child away to live with Grey's family. In the film's climax, the Duke demands that Georgiana return to live with the family but she decides to live with Charles. After the Duke threatens to bar her from seeing all of her children ever again, she changes her mind about Grey and returns to her husband and children and lives out the rest of her days on the family estate.
Some critics and posters here have complained that The Duchess is a story that we've seen too many times before. Maybe so, but it never bores. All the plot points are covered effectively as the protagonist's journey is etched in stark relief. There's the inciting incident where the Duchess learns of her betrothal to the Duke. The break into the Second Act occurs when the Duchess's leaves her 'ordinary' world and marries the Duke. The Midpoint where the stakes are raised, occurs when the Duchess invites Lady Elizabeth into their household leading to further complications. In the words of Christopher Vogler, the protagonist approaches "the inmost cave" at the end of Act II where the protagonist must undergo an ordeal. In The Duchess, Georgiana attempts to defy the Duke and ends up being raped. This is her "All is lost" moment or "Dark Moment of the Soul".
The Dark moment is actually a delayed crisis. It's a huge setback but the protagonist must regroup and once again must push forward. In the beginning of Act III, the protagonist must have some kind of respite before pushing forward into the final battle. In The Duchess, Georgiana's respite is the birth of her son. The Duke's double standard perhaps pushes Georgiana forward into the final battle. She's determined to have her affair with Charles Grey despite her husband's damning prohibition. The Duke however turns the tables on her. He forces her to choose her children over her relationship with Grey and in the end, she surrenders and returns to the family.
Because this is a true story, Georgiana's victory is bittersweet. Due to the time she lived in, women were not permitted the same rights as men. The hypocrisy of the Duke is evident: he is allowed to live in an adulterous relationship with Lady Elizabeth under the same roof but the Duchess is not allowed to see her lover. Nonetheless, the protagonist must 'seize the stone' and take possession of what was being sought in the 'special world' (in this case, Georgiana's quest for the special world of freedom and self-actualization). Since this is 18th century England, the Duchess doesn't exactly 'change the world' but at least she gets her children back, so in that sense she has restored some semblance of balance within her world.
I'm not in agreement with those who disparage Keira Knightley's performance as the Duchess. I found her to be believable and compelling as a woman who heroically asserted herself in the male-dominated society of the time. Ralph Fiennes didn't have much to work with in the role of the Duke. One gets the feeling that the film's writers didn't know much about the Duke of Devonshire historically so they decided to turn him into a stock villain. There was an attempt to mitigate the character's unsympathetic portrait at the end, softening him up by depicting him as being slightly more sympathetic toward the Duchess but it was a little too late. We needed to know more about the Duke—a more nuanced portrait. All we get to know about him is that he liked his dogs and often complained about the food on his plate. And is there any evidence that he actually raped his wife? I think that scene was inserted strictly for dramatic effect but I doubt that it happened.
The Duchess might not be the most original 'period piece' out there, but its focus on domestic violence and how women must cope with it is as relevant today as it was back then.