Birthday Girl takes a huge wad of potential and blows it on trite delivery and implausible twists. John (Ben Chaplin), a dull bank clerk living in a dull English suburb, scopes the Internet for a suitably exotic Russian squeeze and lands on sexy Nadia (Kidman). She's lovely, she likes him, and she wants to play house. She doesn't speak English, so she hardly utters a word. Considering he's a total perv with a cabinet full of B&D porn, the problem is?
John, puzzlingly dissatisfied, tries in vain to return the merchandise. But Nadia convinces him -- largely during a very unpleasant closeup sequence of Chaplin receiving one off at the wrist -- that she's a keeper. As Butterworth and his brother and coscreenwriter Tom know, this is the ideal time for a plot point. They provide this "surprise" on Nadia's birthday, when her alleged cousins Yuri (Mathieu Kassovitz) and Alexei (Vincent Cassel) arrive at John's house for a stay of unknown duration. Mayhem ensues.
It's truly unfortunate that Birthday Girl shoots itself in the foot, because there are plenty of functional elements on hand. Although Chaplin might serve us better as an actual bank clerk than as an actor, he passes here as a Pollyanna with much to learn about life outside his hermetically sealed world. The notion of the nebbish done in by the crafty moll has been done to death, but John's sarcasm ("It's so cold in Russia, you have to go to England and shag to keep warm?") mixes well with Nadia's onionlike layers of deceit. His increasing sympathy for her makes no sense whatsoever, but their emerging chemistry is adequate to sustain curiosity, even when he learns he's just one of the Russian team's long list of scams.
The movie's real drag comes from Cassel and Kassovitz (currently wowing audiences in Brotherhood of the Wolf and Amélie, respectively). They play the Russian gypsy shtick endearingly at first -- strumming guitars and cavorting while perfectly emulating Robin Williams' dubious accent from Moscow on the Hudson. But their performances become so chummy, so cutesy, that the threat they soon pose to John arrives colder than yesterday's borscht.
Kidman, on the other hand, works hard for the money. Who knows what she was slipped to convince her to do this project, but she punches the clock with aplomb. Word has it that she chose Birthday Girl because it was shot mostly in her native Australia at the same time Tom Cruise was there doing Mission: Impossible 2. That weird convenience notwithstanding, she's true to her own mission, and, barring a few slips into Boris-and-Natasha dialect ("You spleet my fucking leep!"), she's the movie's truest element.
A shame, then, that the rest of this endeavor is such a mess, from its clangingly false emotional manipulation to the silliest "suspense" music ever composed on a kazoo. Butterworth is full of good intentions, but we know where those lead, and Kidman's presence, though pleasant, is merely bait for the box office. Like the Molotov cocktail it aspires to be, Birthday Girl is simply a bomb.