It's been a big year for women. From the 18 million ceiling cracks to the conflagration of hockey moms on the national stage, you can't help but hear the crunch of female empowerment. Which sounds like the perfect entrée for The Duchess (opens Fri. Sept. 19), a film about one of 18th Century Britain's most iconoclastic women, Duchess Georgiana Spencer of Devonshire (Keira Knightley).

Unfortunately, director Saul Dibb (Bullet Boy) missed a key memo: If you're gonna make a movie about an iconoclast, you need to show her doing something iconoclastic. Getting crapped on by her husband and birthing loads of babies doesn't exactly count—especially when modern female audiences are used to seeing women whip stadiums of voters into a pro-drilling frenzy.

According to Amanda Foreman's biography and the film's press kit, Georgiana Spencer did all sorts of subversive things, like eviscerate men with her rapier wit and wield gobs of political influence. Too bad we don't actually see any of it, save short scenes where she her takes down some chap at a dinner party and makes a cameo at a political rally (which, we later learn, she only showed up for because she wanted to bang the guest speaker).

The rest of the movie is a 110-minute homily on how royally it sucked to be a woman in the 1700s. Let's see now: Married at 17, ordered to breed like livestock, berated for not delivering a son, raped by her husband, humiliated by his live-in mistress, denied her only lover, and, in a nice kicker, forced to hand off her illegitimate newborn and return in social disgrace. All leading up to a big, climactic finish where our heroine [spoiler ahead—though trust me, it's an act of mercy] does absolutely nothing! She sucks it up, living out her days with the heartless husband and backstabbing mistress in their brocade-filled castle. Here's your inspiring story of a woman battling the odds! The copy line may as well read: "A woman who defied the world...until she didn't."

Knightley pulls off all this distaff misery as best she can, her face emoting debasement and powerlessness—though at times it's tough to tell whether she's just grimacing under those 30-pound wigs. Ralph Fiennes is predictably stellar as Joe-Evil-husband (despite a laughably inconsistent character—it's as if Dibb and his writing team can't bear to let an asshole be an asshole), and the supporting cast, including Swimming Pool's Charlotte Rampling as the joy-killing mother, is strong.

Still, all the good actors and gorgeous period frocks Dibb's budget can muster aren't enough to rescue this plodding mess. Interesting things were happening during Georgiana's life—the Enlightenment, the first rumblings of the French Revolution, King George's nutty reign. But all we—and the Duchess herself—see is vacant prattle and domestic drama inside over-decorated bedrooms and dining halls. Which is perhaps the most depressing part of all.