Don't bother looking for Big Ben or Buckingham Palace in Stephen Frears' Dirty Pretty Things. Its characters share city limits with those landmarks, but they live in a world of gray markets, handshake deals, and bosses who don't pay much attention to immigration status. Though trained as a doctor, African immigrant Chiwetel Ejiofor works a day job as a cab driver and a night job as a hotel porter just to get by, in addition to treating the occasional patient too ashamed or afraid to go through official channels. His reward: a space on the couch in a tiny apartment belonging to fellow illegal worker Audrey Tautou. His world runs on human sweat, and occasionally some blood, with one hungry immigrant eager to fill any position left open by another. The scheming expression worn by Ejiofor's hotel boss, Sergi López, says all that needs saying about Ejiofor's uncaring adopted homeland, or so he believes until he finds a half-flushed human heart, in an early scene that surely ranks as the scariest encounter with a toilet since The Conversation. Turning detective, he learns just how deep immigrant desperation, and others' willingness to feed on it, goes. Working from a script by Steve Knight, Frears has directed a surprisingly sturdy hybrid of thriller and social melodrama, even if the thrills turn ludicrous and the social critique grows a little pat. Tautou doesn't make for the most convincing Turkish national, but she's balanced out by Ejiofor's assured lead and a strong supporting cast, particularly López, who chews scenery as a character who grows more villainous with each scene. He's the ugly face of an otherwise faceless system, and Frears goes to great lengths to map out how that system works. Eventually, the director becomes a little too insistent for the good of the film, but what's come before makes his urgency easy to understand.