Remember when I abruptly declared Anne Hathaway the best actress of her generation? That may have been premature. Unlike Hathaway, fellow 20-something starlet Keira Knightley has a few standout performances to pad her application for my lofty title: "Pride and Prejudice," "Atonement" and the film I watched last weekend: "The Duchess."

Georgiana Cavendish (Knightley) is selected to wed the philandering Duke of Devonshire (Ralph Fiennes) with the express purpose of giving birth to a male heir. As six years pass and the Duchess births two daughters but no sons, she endures the Duke's infidelity by becoming a socialite of sorts. Gambling, politics and fashion are her provinces in 18th-century England. But Georgiana's heart is still consumed by the strain of a love triangle with the Duke and Georgiana's friend Elizabeth (Hayley Atwell) - as well as her passion for the future prime minister Charles Grey (Dominic Cooper).

The film occasionally fails to sustain interest. Most of the conflicts feel tepid and anticlimactic, and the particulars of Georgiana's social life feel glossed over. But Knightley's performance redeems much of the dross. Her Georgiana has a healthy passion for love and slightly scandalous fun that doesn't deter her from devoted motherhood and friendship.

Knightley even holds her own in scenes with Fiennes, whose Duke is a compelling antagonist. Though he is singularly obsessed with his goal of obtaining a son, the Duke otherwise comes off surprisingly neutral and, at times, harmless. That he and Georgiana are last seen together in "The Duchess" blithely chatting at a party - after she bears his son - speaks to this curious facet of his character.

On an un-Knightley related note, "The Duchess" was one of the more impressive Blu-ray releases I've ever watched. The lavish 18th-century English sets and costumes are realized with stunning vividness in high definition, and I can't imagine standard DVD even approaching this superb level of detail.