Downtrodden single parent Carol works in a phone warehouse – from which she steals phones which she sells to a Chinese girl fence called Ying – gets no help with her lazy, vicious sons Dean and Terry from her useless ex-husband Kieran. When Dean attacks his girlfriend Tracey, he and Terry kick an innocent onlooker to death. Carol finds blood on their clothes which they explain as being obtained in a fight and when the police call she initially covers for the boys. Ultimately, she learns the truth from Tracey but Kieran brutally advises her to keep quiet. Carol disagrees and, realising that the boys will turn into copies of their father, knows what she must do.

Illegal Chinese immigrant Ying is dependent upon Gao, brutal leader of the Snakehead gang, who sends her onto the streets of Brixton selling bootleg DVDs and fenced accessories. When she fails to earn enough to pay her keep, he rapes her but, following a police raid on illegal immigrants, Ying flees. She finds sanctuary with Jamal, a kindly, divorced barber and stays with him in return for doing his cleaning. But Gao isn't going to stop.

Ex-heroin addict Richard is determined to stay clean but after being hauled in for police questioning thanks to a crooked friend he misses his contact visit with daughter Sabrina and learns from his ex-wife Yvonne that she and Sabrina are moving to Bristol. She announces that she is planning to deny access. He asks his mother Pam to intervene but she is not keen to get involved. He finds an unlocked and abandoned car belonging to Polish cleaning lady Kasia and persuades a mechanic friend, Zak, to buy it but finds that it has been towed away by the police and returned to Kasia so he breaks into another car and sells a computer to Zak. Eventually he gets to talk to Sabrina through a door, giving her the money, and she gives him hope that he will see her again.

Kasia is informed that her boyfriend Tomek was killed by Carol's sons but there are other shocks to follow. He was also seeing another woman, lap dancer Tara, though when the two meet they actually get on. Tomek was also involved in a racket whereby he and his partner Piotr arranged sham marriages for money to give citizenship to illegal immigrants but Piotr tells Kasia that Tomek gambled away all his earnings and there is nothing for her. Kasia reluctantly agrees to marry Indian Rakesh in exchange for three thousand pounds but discovers a large cache of money hidden at Piotr's flat and realises that he has lied to her. She steals the money, giving some to Tara for Tomek's funeral, and flees with the rest. Piotr gives chase but she escapes from him and gets onto a train where Carol is a fellow passenger.