London, the 1980s. After throwing a brick through an Asian shopkeeper's window, teenage skinhead Trevor is sent to a residential assessment centre by the courts. His social worker Harry escorts him to the centre and hands him over to Peter, the centre's deputy superintendent. To his disgust, Trevor is put in a room with Errol, a black boy.
The following morning, Trevor is given some money for his bus fare to the job centre. Accompanied by Errol, Trevor steals a car and spends his bus money on glue, which he and Errol sniff. Arriving at the job centre, Trevor argues with the employment officer and throws a brick through the centre's front window. Trevor and Errol break into a disused swimming pool where Trevor recovers some hidden tools he uses for house breaking and car stealing. Trevor asks Errol to hide them for him. Peter sees Trevor returning to the assessment centre in the stolen car and tells him to get rid of it.
Because Trevor arrives back late, he misses lunch. The centre's chef refuses to give Trevor any food, so Trevor attacks him. Trevor is restrained and dragged into an empty classroom where Peter, another care-worker, Barry, and the centre's chief superintendent confront him. The chief superintendent explains to Trevor that the assessment centre is his last chance to change before his life becomes a vicious circle of poverty, crime and prison. After the chief superintendent leaves, Trevor tells Peter and Barry that he wants to go to prison and the only reason he is in trouble is because he is fighting for Britain. In an attempt to pacify Trevor, Peter offers to take Trevor banger racing if he promises to behave.
On the way home from the banger racing, Trevor steals Peter's keys and that night he and Errol use them to break into the centre's offices. They find their own assessment records and, after reading them, Trevor urinates on them. Afterwards, the two boys escape from the centre and steal a minibus. They drive to the house of the Asian shopkeeper whose windows Trevor broke and the two of them shout racial abuse and smash the shopkeeper's windows again. Errol falls asleep in the minibus so Trevor drives to a local police station and deliberately crashes into a police car. Trevor flees and the police arrest Errol.
Trevor goes to Harry's house and gets him out of bed. He tells Harry about the job centre and shopkeeper's windows, the stolen keys and the minibus. At Trevor's request, Harry calls the police. Trevor is placed in a cell at the police station and two police officers tell him that he will stay there until his court appearance on Monday morning. One of the officers hits Trevor with a truncheon and informs him that he is facing a sentence in either a youth detention centre or a borstal. The police also tell Trevor that he has made himself a target and when he is released, they will be looking out for him. Trevor grins.
