A vibrant beauty and celebrity of her time is trapped in an unhappy triangle with her husband and his live-in mistress. She falls passionately in love with an ambitious young politician, and the affair causes a bitter conflict with her husband and threatens to erupt into a scandal. - skip ad -   Genres: Art/Foreign, Drama, Adaptation and Biopic Running Time: 1 hr. 45 min. Release Date: September 19th, 2008 (limited) MPAA Rating: PG-13 for sexual content, brief nudity and thematic material. Distributor: Paramount Vantage Cast And Credits Starring: Keira Knightley, Ralph Fiennes, Dominic Cooper, Hayley Atwell, Charlotte Rampling Directed by: Saul Dibb Produced by: Carolyn Marks-Blackwood, Francois Ivernel, Cameron McCracken

No bodices rip in “The Duchess,” an overstuffed, intellectually underbaked portrait of a poor little rich girl, but Ralph Fiennes does take scissors to Keira Knightley’s unmentionables for some shivery snip-snip. Based on a true story, as they say in the movies, the tale traces the cosseted, tightly corseted late-18th-century life of Georgiana Spencer, the Duchess of Devonshire, one of those gilded-cage aristocrats who appear to have been primed, pumped and exclusively prized for the fecundity of their wombs. If the name of another suffering Spencer (guess!) popped into your head, you have made the filmmakers very happy.

A look at both the American and British versions of the trailer for "The Duchess" and how they differ in their emphasis.

Born in 1757, Georgiana went from scampering merrily across the emerald expanse of the family estate under the pitiless gaze of her mother (Charlotte Rampling) to trembling under the unloving touch of the Duke of Devonshire (Mr. Fiennes, very fine). A cold if brilliant catch, the duke took his teenage bride expecting she would instantly bear him a male heir. Fate intervened and the happily ever after never materialized, though the children did pop. She wasn’t scrubbing chamber pots for her keep, but she did have to endure her husband’s dalliances. There were tears and storms, petty and political affairs (along with a little unconvincing Sapphic panting) and, in time, the Amanda Foreman book on which the film is based.

Like most costume dramas of this distaff sort, “The Duchess” wants you to pity Georgiana while also indulging in every luscious detail of her captivity. She may have a pimp for a mother and a bore for a husband, but just look at those verdant landscapes dotted with grazing sheep (no grubbing peasants), the fabulously ornamented gowns, leaning towers of wigs, palatial digs and troops of silent servants. (It’s period-lifestyle pornography.)

Working from the unrevealing screenplay that he wrote with Jeffrey Hatcher and Anders Thomas Jensen, the director Saul Dibb laps it all up and dribbles it back without an ounce of reserve or postempire skepticism, his camera trailing after Georgiana like a dog, a vantage point that badly serves his inexpert star.

A big-boned beauty who leads with her jaw, Ms. Knightley looks pretty as a Gainsborough picture in and out of her silks and satins, but she’s not a remotely composed one. Though now 23, she still tends to throw herself around the room like one of those jangling adolescent girls who, arms and legs pinwheeling, heads bobbing like Halloween apples, have yet to adjust to their newly sprouted bodies. (Modigliani would have loved the willowy bend of her neck if he could have persuaded her to stop fidgeting.) She’s not much of an actress — she pops her eyes instead and thrusts out her chest — but she doesn’t need to be Helen Mirren if she can cultivate a real screen presence. Stillness would become her, as would a good director.

“The Duchess” is rated PG-13 (Parents strongly cautioned). A discreet sexual assault, and the usual aristocratic decadence and vice.