Ben is alone in a shabby flat in Camden Town. He desultorily plays a chord on a violin, and trips over a dirty plate and knife on the floor. His partner, Julie, comes in from work. Ben shouts angrily at her to get out: she is late because she must have been seeing another man. Julie tries to tell him about her day at the office - she works in the civil service - but he continues in his bad temper. He throws her clothes out of the window, so she tells him this time she is really leaving him, and she begins to pack a case. He gets a knife from the kitchen and threatens her - not for the first time. She ignores him and moves towards the door. He cuts her cheek with the knife.

Monica and Gerald, an affluent, married, middle-class couple, are preparing supper in their well-appointed kitchen. They talk about Julie. Gerald is her boss at the office. Monica is aware that Julie is the latest in a long line of Gerald's 'girl friends'. They talk about their children, Carrie and Tom. Monica suspects Tom of being gay, just to spite them. She loathes Gerald and wants to divorce him. In fact, she wants him out by the end of the week, and suggests that, if he wants to live with Julie, he spends a trial weekend with her first.

Gerald and Julie go to a hotel in Suffolk for the weekend. Julie tells him that Ben is sorry he slashed her face and wants her back. However, she is now here, with Gerald. He is nervous and defensive, she is skittish and realistic. She knows she is probably not the first girl he has taken away for a weekend like this, and suspects he finds her annoying. She orders whisky from room service, while he makes tentative and embarrassed preparations for going to bed, undressing in the bathroom. When she finally begins to undress herself, she is discovered to be wearing a swimsuit under her clothes, instead of underwear. Gerald ostentatiously reads a book while he's waiting for her. Julie remembers Ben, suddenly decides that she cannot go through with the charade, and puts her clothes back on again. They drive back to London in the early hours.

The next morning, Monica is preparing breakfast. She tells Gerald that she half expected him to come back early. She tells him that she has been unfaithful to him for years, even with her daughter's boyfriends. She accuses Gerald of being dessicated, delusional, an impotent sexual fantasist, who has never slept with anyone other than her, despite all his boasting. She gloats. Gerald grows more and more discomforted. He picks up the bread knife from the table and plunges it into Monica's stomach. He drags her body into the sitting room and telephones the police.

Ben is surprised to see Julie back. She tells him about her weekend, how Gerald disgusted her and she couldn't sleep with him. Ben tells her that she invites his violence towards her. They start to practice a piece by Vivaldi on the violin and piano.