The mid-1960s. Amir arrives in Britain after a tortuous journey in a vegetable crate as part of an organised immigration racket involving a chain of many people. He reaches a city in the Midlands and is taken to a terraced house by a man known as 'the agent', who demands regular payments for his silence.
Eighteen illegal immigrants live there - Amir shares the top floor room with army veteran Gholam, while would-be writer Sakib lives in the attic and house leader Hussein Shah on the landing below. Lacking technical skills, Amir is given menial work in a textile factory. He is told that the management prefers illegal workers, as they have no rights so can't complain about conditions. Gradually, Amir gets used to the routine, which includes a regular Sunday trip to a Bollywood film and a visit from the local prostitute. He makes a friend in the local café, who finds someone to deliver letters to his wife.
But things change when Hussein Shah starts going out with Mary Collins, a white Irishwoman. Initially nervous, the housemates are gradually won over by her sense of fun, and she in turn loves living with them. Mary tells the men how much she appreciates life with Hussein Shah, who picked her up after her previous boyfriend was murdered when a drug deal went sour. The men tell her exaggerated stories about their lives back home and urge her to convert to Islam. She refuses, but says she appreciates people who have so much to believe in.
Mary becomes pregnant, and Amir hears that his mother-in-law is gravely ill, and he sends more money. This eats into the agent's "fee", which leads to an argument. An outraged Mary throws the agent out. The stress causes her waters to break, and after much panic and assistance from the prostitute (the men don't want to risk ringing a hospital), her son Michael is born.
The men bless the child, but Hussein Shah is suspicious that it isn't his. Despite her recent help, the visits from the prostitute are cancelled out of concern for Michael's moral well-being. Hussein Shah orders Mary to marry his nephew Irshad so he can enter the country legally. She protests, and is supported by the rest of the household, outraged at the thought of two blood relatives sharing a partner. Hussein Shah insists that it will be a paper marriage only, and says that they should instinctively want to support a fellow brother in trouble.
Mary tells Amir in private about her violent family background, which culminated in her mother killing her abusive father. She regards the immigrant household as being the only proper family she's ever had, and is distraught by the prospective change in her status. Later, Amir and Sakib overhear Hussein Shah beating her - after which the marriage goes ahead.
Irshad goes to the textile factory and is rapidly promoted, since he has electrical skills. To Hussein Shah's disgust, he develops a taste for pub visits, and encourages Sakib (who secretly dotes on Mary) to come with him. One night, Amir sees Irshad and Mary kissing. He tells Mary, who reminds him that Irshad is her husband. Soon afterwards, she goes out to the pub with them too. When Hussein Shah catches Irshad and Mary together, he beats him up. Irshad, now resident legally, threatens to call the police.
Amir's café friend dies. Mary invites a larger group out to the pub, which ends in a confrontation between Hussein Shah and Irshad. This continues at home, and culminates in Irshad stabbing Hussein Shah to death. He grabs a traumatised Sakib as he dies, covering him in blood. The rest of the household flees in panic. Amir rings the police.
Years later, a now legally resident Amir bumps into Mary and Michael in a coach station. She reminisces fondly about her time in the house. Just before leaving, she reveals her dark glasses conceal a black eye. Amir goes to see Sakib in a mental institution in the countryside. Sakib's uncle arrives to take him home to Pakistan. Amir strolls contentedly through the fields, finally at peace with himself.
