Ruth Ellis lives with her young son Andy above the bar she manages. Upstairs is a brothel. Ruth is intent on securing better life, sending Andy to boarding school and getting her baby daughter back from her estranged husband.

Through Desmond Cussens, a regular customer who secretly loves her, Ruth meets motor-racing driver David Blakely. Despite early friction, they begin a sexual relationship. From the start, David belittles her job and asks about her sexual history - particularly her relationship with Desmond.

Realising he can't compete with the young, dangerous David, Desmond tries to win Ruth's love by being indispensable, chauffeuring her around in one of his two cars, a Zephyr and a decommissioned taxi. Ruth exploits his generosity, occasionally mocking him behind his back. During a seaside trip, Desmond offers to pay for Andy to attend a boarding school. She accepts.

David takes Ruth to watch him race. She meets his friends, most of whom think her beneath them. One man, Clive, flirts with Ruth. She half-jokingly tells him that David will hit her if he catches them.

When Desmond tells Ruth that David is engaged, she tries to end the relationship. At the Automobile Club Ball, she watches David dance with another woman. Dancing with Desmond, she confides that her former husband used to hit her. Arriving home alone, she finds David in her flat. He says he won't have any peace until they are married; she says she's never had any peace.

David claims he has broken off his engagement, and offers to introduce Ruth to his mother. But when they visit his parents' country house, he makes her wait in the car while he checks that the coast is clear.

David humiliates Ruth in front of his friends, Anthony and Carole Findlayter, by mentioning that Desmond is paying Andy's school fees. Arguing outside the house, David hits Ruth across her face. It is the first of many violent incidents.

David's drunken, aggressive behaviour at the bar costs Ruth her job. Afterwards, David, sobbing, blames the booze. Recovering, he blames Ruth, and pushes her down the stairs. Ruth vents her hurt and frustration by smashing bottles in the bar.

Homeless, Ruth moves in with Desmond, and they begin a sexual relationship. Before long, she is seeing David on the side, and the cycle of abuse recontinues. Desmond finds out and tells her to leave. Still, ever reliable, he helps her move into a boarding house.

Ruth tells David she is pregnant, and offers to have an abortion, but David is opposed. Later, Anthony accuses David of allowing himself to be manipulated. On Anthony's advice, David tries to focus on his upcoming race. Ruth tracks him down in his favourite pub and demands to know why he hasn't returned her calls.

David doesn't win the race, but is asked to drive at Le Mans. To celebrate, he invites Ruth out to dinner, and offers to take Andy to the Hampstead fair. Ruth, on painkillers and tranquillisers after losing the baby, agrees to go out, despite her poor health. When David doesn't arrive, Desmond drives her to his house. David doesn't emerge, but she sees his light come on as she tries to break the windows of his car. She watches the house throughout the next day and into the night, while a party goes on inside. Desmond arrives to find her flustered and disorientated. She's sure, however, that David is with another woman. Desmond takes her to his place, and he starts losing his grip. He tries to force himself on Ruth; she fights him off but then relents. They have sex, but Ruth's mind is elsewhere.

Ruth waits for David outside a pub where, as he walks to his car with Clive, she calls out his name. He turns; she shoots him. Clive tries to shield his friend, but she shoots David several times more.

In prison, Ruth writes a letter to David's mother, telling of her love for a man who was not satisfied with just one woman in his life. Ultimately, Ruth blames the Finlayters for David's death - and her own.