London, the present. During an office meeting, young property developer Jamie is instructed to remove the tenants occupying a highly desirable building in a deprived area of the city. After an initial rejection, Jamie returns to the house with an improved offer.
He discovers a mysterious group of young adults. Emily, the group's leader, refuses his offer. Reporting back to his boss, Jamie is told to spy on the group for any information that would enable the company to legally evict them.
During his next visit, Jamie is invited to accompany the group. He is astonished to witness the tribe selling an extensive range of electrical accessories, including mobile phones and stereos, to eager customers on the streets. Later, Jamie is separated from the rest of the group and threatened by some local youths, who are interested in his camera. The tribe arrives on the scene and the assailants disperse.
At the house, Jamie is offered strange food and invited to look around the house at the next open-day. Meanwhile, Emily meets an elderly Japanese businessman, their primary source for electrical merchandise.
Emily tells Jamie he must have an AIDS test prior to his visit. Jamie has the test and is instructed to eat nothing for 24 hours before the day. Making his excuses at a business lunch with his boss, Jamie meets the group at a café and is given a special potion to drink. He is led through a web of underground caves and tunnels, eventually coming out in the secluded grounds of Darwin's House.
Jamie begins to reveal personal information about his job and life. He is shown round the house and introduced to the group members. He spends the night at the house, engaging in a sexual encounter with Lizzie.
The following morning at work, Jamie bluffs his way through a presentation to some important clients. Driving to the group's house, Jamie is threatened by a local gang. Once again, the sudden appearance of the tribe rescues him. Jamie accompanies the group on a visit to a local religious cult.
The next day, he follows Emily in his car as she secretly visits her parents. Jamie offers to help by stalling his boss's efforts to remove the group from the building. Jamie sees Lizzie and another tribe member selling their merchandise in a restaurant. He ignores her in front of his work colleague, but makes his excuses to leave the table and has sex with her in a backroom.
Walking through a local park, the tribe is attacked by a gang, leaving one member, Ricky, badly injured. At the hospital, the police question members of the tribe. That evening, a local gang breach the security fence and vandalise the exterior of the property. Hiding inside the house, Emily acknowledges to Lizzie that their lifestyle cannot last forever.
Sensing the imminent decline of the group, Lizzie arranges to meet a local newspaper journalist and reveals aspects of their mysterious existence. The story becomes front-page news. Jamie's boss now believes there are sufficient grounds to evict them from the building. Police search the property. Jamie discovers that Lizzie has left the group.
In retribution for damaging their property, the tribe visits the local cult. They distribute free electronic gifts to its surprised members, enraging the leader, Francesco. Emily leads the group to a restaurant to confront Lizzie. Jamie tells Emily he wants to join the tribe. Lizzie is defiant and rejects Emily's concern, arguing that their experiment is now over. Lizzie runs off. On the streets around Piccadilly Circus, the tribe begins to fragment as its members go their separate ways.
At work, Jamie tells his colleague how happy his experience with the tribe made him. Jamie comforts Emily at the group's house, which now has workmen and machinery onsite. At his flat, they make love. Jamie awakes to find Emily pacing the room. She tells him she is leaving and describes an imaginary, chance meeting between them in the future.
