Mark and Colin Pollock are brothers in their twenties, and live with their bad-tempered, quarrelsome parents, Mavis and Frank, in a rented flat in the East End of London. Like much of the local population, Mark, Colin and Frank are all unemployed. The streetwise Mark is a rebel with a caustic wit, who antagonises his parents and shows little regard for his shy, slower-witted brother, who he habitually addresses as 'Dobbin' or 'Muppet'. He spends his days wandering around, or in betting shops and pubs, sometimes in the company of Coxy, an aimless young skinhead with a latent tendency towards racism and violence.
When Colin tries to follow Mark to the pub one day, Mark lets him tag along, and Colin proves to be a good pool player. Coxy seems to befriend him and subsequently takes him to visit Hayley, a young friend of the group, in her flat. However, while they are there Coxy cruelly taunts and teases Hayley, almost reducing her to tears, and later shuts Colin up in a cupboard as a joke. When Mark learns that Colin has been keeping company with the dangerous, unpredictable Coxy, he becomes worried for his brother.
Mavis's sister, Barbara, lives in the middle-class district of Chigwell, in a loveless marriage with businessman John. She offers to pay Colin to paint and decorate their house. Mark, who feels that the offer is demeaning and patronising, gets to Barbara's house first on the day that Colin is due to start work, and pretends that Colin has got lost. The two of them drive around looking for him, only to find Colin waiting outside the house when they return. Mark urges Colin to go home with him. Colin, who believes that Mark wants the decorating job for himself, leaves, and goes to Hayley's flat, but she will not let him in.
John returns home from work that evening to find that Barbara has been drinking heavily, and his pompous, high-handed attitude provokes her into swearing at him. Mark and Colin arrive back at their flat separately, Colin enveloped in his voluminous parka, which he refuses to remove. Mavis and Frank are furious that Colin has walked out of the job Barbara had offered, and berate him and Mark in the bedroom that the brothers share. The usually mild-mannered Colin suddenly snaps and orders their parents to be quiet and get out of the room. Left alone with Colin, Mark tells him that he loves him, and says that he intends to leave home. In the morning, he discovers that Colin has had his head shaved. Colin denies that Coxy influenced this decision, and Mark approvingly agrees that no one should tell him what to do. As he leaves, he gives Mark a new nickname: 'Kojak'. Colin protests, but he is smiling. In another room, their parents continue to argue.
