The action of the play may be assumed to take place over a period of many months, or even a few years. Len, a young London man, and Pam, a young London woman whom he has just met, are the play's central characters. The play opens with Pam bringing Len back to her house. They eat sweets. When Pam's father Harry passes, Len and Pam offer Harry candy laced with innuendo. Pam is amused by Len's behaviour. This scene ends with the intimation that Pam and Len are having sex.
Len and Pam go boating on a lake in a local park. Pam is showing signs of being bored with Len. In charge of the boats is Fred, a friend of Len's. He shows interest in Pam. Len becomes a lodger in Pam's house, although Pam has now left him for Fred. It is clear that Fred does not treat her well, and Len is sympathetic. Pam is grateful for the sympathy, although she finds Len irritating. Pam becomes pregnant by Fred, and has his baby. Pam's mother Mary becomes fond of Len, although Pam gets increasingly annoyed by his presence in the house. Over the course of one scene, Pam fights with Len and with her mother Mary while the neglected baby cries continually. When Len suggests that something needs to be done about caring for the baby, Pam responds "Put it on the council", i.e. hand it over to child welfare authorities.
Fred goes fishing, watched by Len. Fred confides in Len that he is disenchanted with Pam. Fred and Len's friends Pete, Colin, Mike and Barry turn up, as does Pam, who is wheeling the baby in a pram. Not wanting to be left in charge of the baby, Fred loses his temper with Pam, who in turn becomes angry and leaves the baby with him.
Len leaves. Pete, Colin, Mike and Barry tease the baby, at first harmlessly then with increasing roughness. Fred does nothing to stop them. Barry observes that babies are only animals that don't feel pain. When the baby dirties its nappy, they rub its face in the mess. The violence escalates as they strike the baby and ultimately throw stones at it, Fred joining in. The park is about to close and they run off, Fred returning only to fetch his fishing tackle. Pam returns to retrieve the baby and talks to it absently, not having noticed that it has been stoned to death. Still oblivious, she wheels it away.
Fred is sent to prison for his part in the baby's death, but far from accepting responsibility he is chiefly outraged at the way the crowd outside the prison was treating him. Len admits to him that he saw them attack the baby, but didn't intervene. Fred's response is that that will not help his case. He has finally finished with Pam.
Len is still lodging with Pam and her parents. Pam is hoping that Fred will get back together with her when he is released from prison. Len feels a sexual attraction to Mary, Pam's mother, and flirts with her; she is flattered, but doesn't act on it.
Pam and Len go to a coffee bar, where Fred will come to celebrate his release. Fred, Colin, Pete, Mike, Barry and Fred's new girlfriend Liz turn up. Although Fred is glad to have been released he is edgy and tense, and is disgruntled to notice that Pam is there. When Pam confronts him and asks for him back, he explodes and calls her a "bloody menace", before leaving in disgust. The others follow, except for Len. Pam finally realises that Fred does not love her, and Len offers himself as a substitute, although she does not respond.
Harry confronts Mary about flirting with Len. They argue, and she hits him on the head with a teapot. A chair is also broken. Len helps Harry fix himself up and Harry reveals that he does not bear Len a grudge. Harry tells Len that Len's problem is that he didn't get to fight in World War II : "Yer never got yer man", i.e. Len has never killed anyone in combat.
In the final scene, Len slowly and methodically repairs the broken chair while Harry does his football pools, Pam reads a magazine and Mary does housework. The otherwise entirely silent scene contains only one line of dialogue, from Len to Pam: "Fetch me 'ammer." Although he ends up having to fetch the hammer himself, the family has not completely disintegrated.
Edward Bond described the end of the play as "almost irresponsibly optimistic".