As anyone who's seen Midnight Express and Brokedown Palace knows, certain Asian countries have Draconian penalties for foreigners who get caught trafficking drugs, or even get accused of trafficking drugs. Transsiberian raises the specter of those punishments in Russia, as a couple of American tourists get inadvertently mixed up with drug smugglers on a train whipping through the barren landscape of a Russian winter -- a great setting for such a story. Unfortunately, writer-director Brad Anderson and co-writer Will Conroy subject their heroine (played by Emily Mortimer) to a moment of such patently stupid and unbelievable behavior, halfway through the film, that it sends the rest of the movie off the rails, so to speak. It's even more problematic that this impulsive act, a wild overreaction to the circumstances she's confronted with at the time, creates the chain reaction that becomes the remainder of the narrative. Until that point, Anderson and Conroy have established an interesting interpersonal dynamic between the four travelers, whose relationships are being tested both within and between each couple. A slow-burn of increasing intensity could have grown out of this scenario, but instead, the film gives itself over to the showier realm of Russian mobsters and corrupt police officers playing cat-and-mouse with the principle characters. Whenever the action leaves the train, which is a disappointingly regular occurrence as the narrative advances, it completes Transsiberian's departure from the smart, self-contained thriller it could have been. The film is still watchable during those lesser moments, it's just more conventional than it needed to be, or prepared us to be. Ben Kingsley is good as a Russian cop, but Mortimer's otherwise strong performance is tainted by the momentary lapse of reason written for her character.