Birthday Girl

Nicole Kidman is riding high off her successes in “Moulin Rouge” and “The Others,” but “Birthday Girl” is liable to suck some of the wind out of her sails. It’s a fast-moving, original film for the first 45 minutes, and a deathly tedious one for the next 45. It balances out to be mediocre.

Kidman plays Nadia, a Russian mail-order bride sent for by John (Ben Chaplin), a shy, ordinary English banker. When she arrives, she is revealed to be not all she claimed. She doesn’t speak English, for example — she answers every question “yes” — and she vomits from the car window on the way home.

Her redeeming quality, John soon learns, is that she loves to have sex. They begin a physical relationship, mixed with futile attempts on both parts to learn one another’s language and culture.

This stuff is funny, and it breezes by quickly. Soon Nadia’s friends from Russia have arrived, two rough characters (played by Vincent Cassel and Mathieu Kassovitz) with schemes up their sleeves. This changes the scene drastically, and it keeps changing for the next several minutes, always staying fresh and entertaining.

At the half-way point, there’s a major plot development spurred by the two Russian visitors. From then on, it’s more a thriller and road movie than a romantic comedy, though elements of that genre still peek through. It is far less successful here: We’re so accustomed to the high-flying loopiness that the change of pace doesn’t go down smoothly.

Kidman, though mired in a mediocre film, is as winsome and likable as we’ve come to expect. Chaplin, too, is sweetly bashful as John, and Cassel and Kassovitz add a lot of energy as the two insane Russians.

If the film had somehow resolved itself before downshifting, it would be a marvelous piece of work. Unfortunately, it kept going. Not much of a birthday present, if you ask me.

C (; R, very strong sexuality, some nudity, some.)