In Woman at Point Zero, Nawal El Saadawi describes her experiences as a psychiatrist in Egypt, studying the psychological effects of prison on female prisoners. She states in her introduction that when she was conducting these studies, she had no idea that one day she would be imprisoned by the government. On one visit to Qanatir prison, Nawal meets a doctor who tells her that there is a prisoner there who is truly remarkable. She is awaiting the death penalty for killing a man, but the doctor cannot believe that this woman is capable of killing anyone. He wrote out a request for a pardon, but the condemned woman refused to sign it. Nawal desperately wants to meet with this woman, named Firdaus, but Firdaus keeps refusing to meet with her. Finally, the day before she is to be put to death, Firdaus agrees to meet with Nawal.

Nawal goes to Firdaus's cell, and Firdaus commands her to sit on the ground. Firdaus begins to tell her life story. She was born into an extremely poor family in the countryside. Her father often beat her mother; sometimes he beat her as well. Firdaus used to play in the fields with other children. A boy named Mohammadain was her special playmate, and when they were young, they used to play “bride and bridegroom.” Firdaus got pleasure from her sexual experiments with Mohammadain. One day, her mother performed a clitoridectomy on her, and after that, Firdaus is no longer allowed to play with Mohammadain, nor does she ever feel sexual pleasure in the same way. Soon, Firdaus's mother and father die, and Firdaus is sent to live with her uncle, a scholar, who lives in Cairo.

At first, everything goes well for Firdaus in Cairo. She and her uncle get along well, and she is allowed to go to school, which she loves. She and her uncle share a bed and are close. Her uncle gets married and the new wife does not like Firdaus, so Firdaus is sent to a boarding school. Firdaus is an excellent student and works hard. Unlike the other girls, she does not fantasize about boys and marriage. She spends most of her time at the library and in the courtyard, where she encounters a teacher named Miss Iqbal, with whom she forms a friendship. When Firdaus graduates, she is given an award, but she and her family are not at the ceremony, so Miss Iqbal accepts it for Firdaus. When school is over, Firdaus's uncle comes to get her.

Back at her uncle's house, Firdaus is miserable. One night, she overhears her aunt and uncle discussing whether they will marry Firdaus to her aunt's old uncle, Sheikh Mahmoud. He is sixty and has a facial deformity. Firdaus runs away, but while she is on the streets, she is terrified by the strange men who approach her, so she returns home. They marry her to Sheikh Mahmoud. He is selfish and stingy and beats Firdaus. His facial deformity is a large swelling on his chin with a hole in the middle that leaks pus. After one bad beating, Firdaus runs away. She ends up in a coffee shop, where she meets Bayoumi, the coffee shop owner. She goes with him to his apartment. At first Bayoumi is kind to Firdaus. Then Firdaus announces that she wants to get a job, and Bayoumi is enraged. He beats her and begins to lock her in the apartment when he leaves. He brings his friends home and allows them to abuse and rape her. Firdaus escapes with the help of a neighbor and flees Bayoumi's apartment for the city.

Resting by the Nile, Firdaus feels hopeless until an wealthy-looking woman approaches her. Her name is Sharifa, and she is a prostitute. She takes Firdaus in and teaches her to become a high-class prostitute. Sharifa makes money from Firdaus's body until one night when her friend Fawzy comes over. Firdaus overhears Sharifa and Fawzy fighting over who will get to keep her, so she runs away again. Still a prostitute, Firdaus becomes her own boss and eventually has a beautiful home and expensive things. One night, a client named Di'aa tells her that she is not a respectable woman, and Firdaus is devastated. She gives up her nice apartment and beautiful things, moves into a shack, and begins working as an office assistant. There, she realizes that the life of an assistant is in many ways worse than the life of a prostitute. She meets a man named Ibrahim, and falls in love with him. They have a relationship, and Firdaus begins to feel that the world is not so horrible, until she discovers that Ibrahim has become engaged to the boss's daughter.

Firdaus leaves the company and becomes a prostitute again. She is very expensive and very popular. Many powerful men come to her, and she turns some of them away to prove that she has power over her own body, and because she despises them. Ibrahim comes to her, and she realizes he never loved her; rather, he just wanted free sex. A pimp tries to take over Firdaus's life, and for a little while, she lets him. Then they fight and she kills him. Shortly after that, Firdaus meets an Arab prince who takes her home and offers her $3,000. She sleeps with him, rips up the money, and slaps him. Terrified, the man calls the police. They come and arrest Firdaus. Firdaus is tried and sentenced to death.

She is, she tells Nawal, just waiting to die, because she is excited to go somewhere new. She knows that the men who sentenced her want to kill her because they're afraid of the truth she has to tell, not because they're afraid she'll kill again. After she finishes her story, police come to her cell and take her away to be executed. Nawal leaves the cell and is ashamed of the world. Everywhere she looks, she sees lies and unhappiness. As Nawal drives away from the prison, she thinks about running people over with her car, but she doesn't. She realizes that Firdaus is braver than she is.