Three young offenders - Carlin, Angel and Davis - arrive at an unnamed borstal. Senior Officer Mr Sands tells Carlin, who has been transferred from another institution for hitting an officer, that he will not stand for any trouble. Carlin is put in a dormitory along with, amongst others, Banks, the toughest boy in the borstal known as 'the Daddy'. The following day an officer warns Banks about Carlin's reputation. Later, Banks beats up Angel.

Carlin is sent to work in the laundry with Archer, who wears no boots as he has told the Governor that he is a vegetarian and cannot wear leather. Later Banks tells Davis that he is the Daddy and Davis will have to give him a cut of his tobacco allowance. That night Banks and his friend Richards beat up Carlin as he lies in his bed and warn him not to forget that Banks is the Daddy. A radio is planted in Davis' cell; he is accused of stealing and sentenced to 3 days solitary confinement. Carlin, whose face is bruised, is accused of fighting and brought before the Governor. He is also sentenced to 3 days in solitary confinement. Archer informs the Governor - a strict Christian - that he is still atheist, but thinking of becoming a Muslim.

Upon his return to the wing, Carlin beats up first Richards, then Banks and assumes Banks' position as Daddy, including his lucrative money laundering scam. Mr Goodyear the house officer gives Carlin a single cell in exchange for Carlin's assurance that he will use his position of Daddy to help maintain order. During recreational time, an officer organizes a brutal game of 'murderball', black inmates versus white.

A boy from another wing challenges Carlin's position of Daddy. They arrange to meet in the boiler room. Carlin beats the challenger with a metal pipe, reaffirming his authority. Later Carlin explains to Rhodes, a boy new to the block, that he is not gay, but wants Rhodes to be his 'missus'.

As an atheist, Archer refuses to attend Sunday prayers with the other boys. Instead he is left with Mr Duke, a veteran officer. Archer explains that, contrary to Duke's belief, borstal cannot build character, as it is an institution based on degradation. While working in the greenhouse, Davis is raped by two other boys. Mr Sands witnesses the rape, but does not prevent it. That night, Davis kills himself in his cell.

At lunch the following day, the boys refuse to eat as a protest at Davis' death. Carlin throws his dinner tray at the wall and a riot breaks out. Later, the riot's suspected ringleaders - including Carlin and Archer - are handcuffed and beaten by the officers. The Governor addresses all the boys in the parade ground and there is a minute's silence in Davis' memory.