The film begins at Heathrow Airport, where Lena, a polish immigrant (Olga Fedori) is working her shift as a cleaner. While there, her colleague Birdie (Ainsley Howard) helps her to clean the toilets. Lena talks about her family and living alone in Hounslow. Lena pulls out a mirror that her grandmother left her, and Birdie takes a shine to it. They get some sandwiches, and Birdie introduces Lena to her adopted brother Elbie (Toby Alexander). Lena tells Birdie that she doesn’t get on with her family. Birdie tells Lena that her family care for her, and that they work at the airport too.Lena tries to get Elbie to talk to her, but he doesn’t respond. Later, Birdie tells Lena about someone they know who has a dirty sexual fetish, before stealing an MP3 player from the office. She tells Lena that people shouldn’t leave things lying around if they don’t want them stolen. Lena sees some scars on Birdie, and she tells her that she used to have behavioural problems but she is better now.Afterwards, Lena misses her bus home, and Birdie invites her to stay at her house, near the end of the runway. They climb through a hole in the fence, and enter the house through the back door. Lena discusses how difficult it is to keep in touch with her family.Birdie disappears up the stairs, and Lena decides to look around the house for a while, only for Dad (Perry Benson) to knock her out, and inject her with something. She wakes up in a dark room after hearing tortured screaming. She gets mad, and Dad arrives with Mum (Dido Miles), who tells Lena that when she gets mad, Dad gets excited, and they need to calm him down. Dad spits on the floor, and then leaves the room. Mum tells Lena that as long as she is with her, Dad won’t hurt her.Lena is unable to speak, and Mum tells her not to try to talk, because she has had a little jab. She gives Lena another injection, and Lena falls asleep. She wakes up later, tied to a frame. Mum tells her that she wanted another girl to come and live there. Mum then pierces Lena’s skin with some metal and carves some marks into her back.Mum takes Lena in to see Dad, who is masturbating. When he finishes, he tells Lena that in his house, she abides by his rules. He then grabs her by the throat, before sending her to bed, The next morning, Birdie cleans Lena’s scars and she shows her the scars on Elbie’s back, which she compares to crazy paving.At breakfast, the family are watching pornography, as Birdie plays with Lena’s mirror. She then puts the MP3 player into a pot, and tells Mum that she couldn’t get any more stuff because she was doing Lena’s work. Lena tries to escape, but Dad grabs her and tells Mum to control her children. Elbie drags her on to a chair, and Mum tells her not to go anywhere.Birdie takes Lena through her chores, and tells her that Elbie has nothing going on in his head or in his pants. Mum arrives and tells Lena that she is doing a good job. In her room, Lena attempts to escape, but hears Dad watching her through the keyhole.At breakfast the next day, Lena sees that Birdie has been hiding money from the family and takes it from her pocket. Dad accuses Birdie of lying to the family and shouts at her. Mum sends her to her room, where she cries before making a mess of what Lena has tidied up. When Elbie arrives, Birdie tells him that Lena is his replacement, and he shoves her to the ground. She compares him to the
