Act 1 opens on a dismal Sunday afternoon in Jimmy and Alison's cramped attic in the Midlands. Jimmy and Cliff are attempting to read the Sunday papers, plus the radical weekly, "price ninepence, obtainable at any bookstall" as Jimmy snaps, claiming it from Cliff. This is a reference to the New Statesman, and in the context of the period would have instantly signalled the pair's political preference to the audience. Alison is attempting to do the week's ironing and is only half listening as Jimmy and Cliff engage in the expository dialogue.
It becomes apparent that there is a huge social gulf between Jimmy and Alison. Her family is upper-middle-class military, perhaps verging on upper class, while Jimmy is decidedly working class. He had to fight hard against her family's disapproval to win her. "Alison's mummy and I took one look at each other, and from then on the age of chivalry was dead", he explains. We also learn that the sole family income is derived from a sweet stall in the local market—an enterprise that is surely well beneath Jimmy's education, let alone Alison's "station in life".
As Act 1 progresses, Jimmy becomes more and more vituperative, transferring his contempt for Alison's family onto her personally, calling her "pusillanimous" and generally belittling her to Cliff. It is possible to play this scene as though Jimmy thinks everything is just a joke, but most actors opt for playing it as though he really is excoriating her. The tirade ends with some physical horseplay, resulting in the ironing board overturning and Alison's arm getting a burn. Jimmy exits to play his trumpet off stage.
Alison and Cliff play a tender scene, during which she confides that she's accidentally pregnant and can't quite bring herself to tell Jimmy. Cliff urges her to tell him. When Jimmy returns, Alison announces that her actress friend Helena Charles is coming to stay, and it is entirely obvious that Jimmy despises Helena even more than Alison. He flies into a total rage, and conflict is inevitable.
Act 2 opens on another Sunday afternoon, with Helena and Alison making lunch. In a two-handed scene, Alison gives a clue as to why she decided to take Jimmy on—her own minor rebellion against her upbringing plus her admiration of Jimmy's campaigns against the dereliction of life in postwar England. She describes Jimmy to Helena as a "knight in shining armour". Helena says, firmly, "You've got to fight him".
Jimmy enters, and the tirade continues. If his Act 1 material could be played as a joke, there's no doubt about the intentional viciousness of his attacks on Helena. When the women put on hats and declare that they are going to church, Jimmy's sense of betrayal peaks. When he leaves to take an urgent phone call, Helena announces that she has forced the issue. She has sent a telegram to Alison's parents asking them to come and "rescue" her. Alison is stunned but agrees that she will go.
After a scene break, we see Alison's father, Colonel Redfern, who has come to collect her to take her back to her family home. The playwright allows the Colonel to come across as quite a sympathetic character, albeit totally out of touch with the modern world (as he himself admits). "You're hurt because everything's changed", Alison tells him, "and Jimmy's hurt because everything's stayed the same".
Helena arrives to say goodbye, intending to leave very soon herself. Alison is surprised that Helena is staying on for another day, but she leaves, giving Cliff a note for Jimmy. Cliff in turn hands it to Helena and leaves, saying "I hope he rams it up your nostrils". Almost immediately, Jimmy bursts in. His contempt at finding a "goodbye" note makes him turn on Helena again, warning her to keep out of his way until she leaves. Helena tells him that Alison is expecting a baby, and Jimmy admits grudgingly that he's taken aback. However, his tirade continues. They first come to physical blows, and then as the Act 2 curtain falls, Jimmy and Helena are kissing passionately and falling on the bed.
Act 3 opens as a deliberate replay of Act 1, but this time with Helena at the ironing-board wearing Jimmy's Act 1 red shirt. Months have passed. Jimmy is notably more pleasant to Helena than he was to Alison in Act 1. She actually laughs at his jokes, and the three of them (Jimmy, Cliff, and Helena) get into a music hall comedy routine that obviously is not improvised. Cliff announces that he's decided to strike out on his own. As Jimmy leaves the room to get ready for a final night out for the three of them, he opens the door to find Alison, looking like death. Instead of caring for her he snaps over his shoulder "Friend of yours to see you" and abruptly leaves.
After a scene break, Alison explains to Helena that she lost the baby—one of Jimmy's cruellest speeches in Act 1 expressed the wish that Alison would conceive a child and lose it—the two women reconcile but Helena realises that what she's done is immoral and she in turn decides to leave. She summons Jimmy to hear her decision and he lets her go with a sarcastic farewell.
The play ends with a sentimental reconciliation between Jimmy and Alison. They revive an old game they used to play, pretending to be bears and squirrels, and seem to be in a state of truce.