Okwe (Ejiofor) is an illegal immigrant from Nigeria who was a doctor in his native country but had to flee under mysterious circumstances to London. There, he supports himself by working as a cab driver by day and a hotel desk clerk by night, chewing khat leaves to stay awake throughout his long shifts. He rents a couch from one of his coworkers at the hotel, Senay (Tautou), a Turkish woman who, though she is in the United Kingdom legally, is forbidden to work under her status as an asylum seeker. His other acquaintances include Ivan (Zlatko Buric), a burly Russian who works as the doorman for the hotel, Juliette (Sophie Okonedo), a lower class English prostitute who meets her clients there, and Guo Yi (Benedict Wong), a Chinese doctor who works in a hospital mortuary and supplies Okwe with prescription drugs for the other illegals employed at his taxi company on the sly. Overseeing operations at the hotel is Juan (Sergi Lopez), a suave but shady Spaniard with his fingers in all manner of sleazy goings-on.
One day, Okwe makes a disturbing discovery while investigating a clogged toilet in one of the rooms - a recently removed human heart. Realizing that there has likely been foul play, the highly moral and conscientious Okwe begins to investigate despite being advised by both Juan and Guo Yi not to involve himself. Complicating his efforts to uncover the truth is his immigration status - because he's in the country illegally, he can't go to the police, and he has to be careful who he crosses because anyone who learns the truth about him can report him. Senay, meanwhile, is forced to dodge the investigations of a pair of immigration officials who are convinced she is working illegally, which complicates her budding friendship with Okwe and threatens her dream of saving enough money to start a new life in America with her cousin. Okwe is determined to both uncover the circumstances of the mysterious death and help Senay, but as he says himself, justice may be an impossibility when simply surviving is so difficult.
This film contains examples of the following tropes:
- Almighty Janitor: Okwe is probably the most competent person in the movie despite the menial jobs he does; Senay is no slouch either.
- Becoming the Mask: Juan tells the people for whom he forges passports that this is necessary to fully embrace their new identities.
- "Blackmail" Is Such an Ugly Word: Throughout the movie various people use their illegal status to blackmail both Okwe and Senay. Juan is particularly vicious about it, though.
- Bookends: The movie begins and ends with Okwe at the airport.
- Chess Motifs: Okwe and Guo Yi are fond of playing chess with each other, and at one point the latter makes an analogy between the game and Okwe's situation.
- Dark and Troubled Past: At one point Juan claims Okwe has one of these; He's lying, sort of.
- Dirty Old Man: Senay's boss at the sweatshop she begins working at after she leaves the hotel; he forces her to give him sexual favors in exchange for not turning her into the police.
- Earn Your Happy Ending: Okwe and Senay both manage to escape from their situation and start new lives, but not without hardship and suffering.
- Everyone Can See It: Both Ivan and Guo Yi claim that it's patently obvious that Senay is in love with Okwe and think he's too blind to see it. He's not, but he's too hung up on his dead wife and concerned about endangering Senay's safety to reciprocate her feelings.
- Groin Attack: Just about the most richly deserved one ever. Senay's disgusting boss at the sweatshop demands a blowjob, lest he report her to immigration. The first time she complies, but the second time she bites down hard and makes a run for it.
- Hoist by His Own Petard: Happens to Juan, who has his own kidney stolen and sold on the black market by Okwe after he'd made himself a great deal of money selling the organs of others.
- Idiot Ball: Juan picks it up in a big way when he believes that the beer Okwe gives him before the operation on Senay is to steady his nerves and drinks it.
- Innocent Cohabitation: Okwe and Senay; Senay works very hard to make sure nobody will even think it's not so.
- Laser-Guided Karma: Juan, who has extorted organs out of immigrants in exchange for passports, ends up getting his own kidney removed and sold.
- The Lost Lenore: Okwe's wife, who was murdered in retaliation when Okwe refused to cover up criminal activities for his superiors in Nigeria. Her death continues to haunt him.
- Match Cut: A very dark one, as Senay's upper body rocks back and forth as she's being quasi-raped by Juan, to Okwe's upper body rocking back and forth as he honks the horn of his car, while he's stuck in traffic.
- My Girl Is Not a Slut: Justified with Senay, who because she comes from a conservative Muslim background is very sensitive about the possibility of anyone perceiving anything untoward going on between her and Okwe. She ends up losing her virginity in about the most awful way possible.
- Organ Theft: Not so much theft as forced trade, as Juan runs a lucrative operation illegally harvesting kidneys from illegal immigrants in exchange for fake passports that will give them legal status. Later, however, it's played straight in about the awesomest way possible when Okwe and Senay outwit Juan and steal his kidney after receiving new identities from him.
- Parking Garage: Juan is driving out of the hotel parking garage when he's intercepted by Okwe. A tense confrontation ends with Okwe saying he'll perform the surgery on Senay himself, to make sure she doesn't die.
- Rape as Drama: Poor Senay is forced to give oral sex to her sweatshop boss in exchange for protection and is later forced to give up her virginity to Juan.
- Sexual Extortion: Juan demands that Senay should have sex with him in exchange for a passport.
- Slipping a Mickey: This is how Okwe and Senay knock out Juan before taking his kidney.
- Title Drop: Indirectly; the title references a remark Juan makes to Okwe, which is that it is the job of people like themselves to make pretty again the things which their customers get dirty.
- Worthless Foreign Degree: Okwe was a doctor in Nigeria but because of his immigration status must make his living as a cab driver and hotel desk clerk in London.