“Dirty Pretty Things” manages to make the unlikely subject of the black market kidney trade both funny and touching, without dulling the shock factor — no small feat.

The film, directed by Stephen Frears, is set in London and follows Okwe (Chiwetel Ejiofor), an illegal Nigerian immigrant who works as a cabby during the day and a hotel desk clerk at night. Once a doctor in Nigeria, Okwe is forced to go on the lam when accused of a serious crime. He finds shelter with Senay (Audrey Tautou of “Amelie”), a Muslim refugee from Turkey, who works as a maid in the hotel, violating laws that prohibit refugees to work. Both are dogged by immigration officials and are subjected to shocking and compromising situations.

As they struggle to go undetected in London with the help of a Chinese coroner, a Russian bellhop and a prostitute, their situations become desperate. After finding a hotel toilet clogged with a human heart and a Somali gutted for his kidney, Okwe uncovers an unsettling trade in internal organs operated by his employer, Sneaky (Sergi Lopez).

Nonprofessionals perform the operations, leaving illegal immigrants on the brink of death in their search for money and counterfeit passports. Sneaky discovers that Okwe is trained in medicine and attempts to convince Okwe to join the trade. Only when Senay resorts to the operation to pave her way to America does Okwe agree. The movie serves up a shocking twist at this point that left much of the audience open-mouthed.

The movie does a convincing job of showing London’s tense underworld of illegal immigrants and unseen toilers. However, the film’s most poignant moments are found when the characters interact with one another and ruminate on religion, culture and love. At one point, Senay is forced to give up her virginity to Sneaky in return for her credentials. She is comforted by a prostitute, Juliette (Sophie Okonedo), who laughs at the friendship of “the virgin and the whore.”

In show-stealing scenes, Okwe plays chess with Chinese coroner Guo Yi (Benedict Wong), while discussing Buddhism and green tea, which Guo Yi refuses to drink. The scenes paint a startling picture of acculturation, in that Guo Yi is in many ways no longer Chinese nor religious. But in a telling action, he sews a dead Chinese man’s pockets closed in keeping with Buddhist tradition and mourns the man’s lack of family, a trait that is uncharacteristic of Chinese culture.

Tautou plays Senay as a 22-year-old child dreaming of America in such an idealistic way it will make any American viewer cringe. While Tautou is convincing, the part could have been played by a number of other actresses, unlike the title role in “Amelie.” Any movie patrons looking for Tautou’s lyricism and dynamic facial expressions from France’s highest grossing French-language film to date will be disappointed.

Ejiofor plays Okwe as unyieldingly and mournfully moral and reticent, almost to the point of being frustrating, constantly debating and then resisting Sneaky’s corruption as long as possible. Senay and Okwe’s relationship is unresolved in the film because according to Guo Yi, Okwe doesn’t recognize Senay’s love because he is good at chess and, thus, bad at life. The nicely understated love spirals into tiresome “I love you”s and “hold me”s at the end and is unfulfilling.

“Dirty Pretty Things” is an interesting political and cultural statement, building sympathetic characters the audience will appreciate. The legal struggles the characters deal with can be repetitive, but it is worthwhile to see them genuinely interacting with each other in their small niches in the larger, colder world.