The novel starts with a scene in the Thomas family’s one-room apartment, as Bigger and his brother Buddy chase and kill a rat. Over breakfast, Bigger’s mother keeps asking Bigger if he’s going to take the job he’s been offered because, if he doesn’t, the relief organization will stop giving them food. Bigger meets up with his friends and makes plans to rob Blum’s store. At the movies, however, he sees a show about some of the wealthy families in Chicago, including the Daltons, who are offering him the job. It makes Bigger long for a different life. Instead of robbing Blum’s store, Bigger initiates a fight with his friend Gus.
Bigger goes to the Daltons’ house and gets the job, but while he’s talking with Mr. Dalton, Mary comes inside and asks Bigger if he belongs to a union. Then she tells him he should belong to a union. He makes her uncomfortable and he’s worried that he’ll lose his job. Mr. Dalton doesn’t take away the offer of a job. Instead, he tells Bigger his first responsibility is to drive Mary to the university that evening. Bigger understands that Mary Dalton is crazy and he needs to be careful around her. That evening, instead of the university, Mary directs him to drive her to meet up with Jan Erlone, her boyfriend and a Communist activist.
Jan and Mary want to experience the South Side of Chicago where all the black people live. They pressure Bigger into coming to a local restaurant with them, and manage to make him feel ashamed and alienated. They also all get drunk. After Bigger drops Jan off, he takes Mary home, but she’s too drunk to make it up to her bedroom without help. As he takes Mary upstairs, Bigger gets turned on because of the intimacy of the moment and the way she’s acting. But, the blind Mrs. Dalton appears, wondering if Mary’s arrived home. Bigger, afraid he’s going to be caught in a white woman’s bedroom, smothers Mary’s little noises with a pillow so the mother won’t know he’s in the room. After Mrs. Dalton leaves, Bigger discovers that he accidentally suffocated Mary to death. He doesn’t know what to do. It was an accident, of course, but he’s worried that the justice system won’t believe him since he’s black. Bigger stuffs Mary’s body into her luggage trunk, and takes the body downstairs. There, Bigger manages to get her body into the furnace after hacking off her head. Bigger hopes that the body will burn by morning.
Bigger decides to pretend like everything’s normal. He visits his girlfriend Bessie, where he hatches a plan to write a ransom note and try to getting a lot of money from the Daltons. The ransom never pans out because some journalists at the Daltons’ house discover Mary’s body in the furnace. Bigger takes off running and heads to Bessie’s apartment. Bessie is scared to flee with him, scared to stay with him, and scared to be caught by the police. Bigger realizes he can’t leave her behind to tell the cops everything, but he knows she doesn’t have the fortitude to run with him. He rapes Bessie, kills her, and stuffs her body in an airshaft. Afterwards, he takes off, looking for a place to hide from his pursuers. He ends up hiding on the roof of a house then leaping from roof to roof to escape the men seeking him. In the end, though, he’s caught and taken to jail
Jan befriends Bigger, despite what Bigger has done, and provides him with a lawyer, Boris Max. Max argues that Bigger is the product of society’s racism and oppression. Though he is guilty, he had few other options and was pushed to his life of crime by forces outside of his control. Thus, he should be sentenced to life in prison instead of getting the death penalty.
The judge of Bigger’s case orders that Bigger should be put to death for his crime. During this time, Bigger begins to trust Max. This is the first white person he’s ever trusted in his life. Bigger begins to realize that whites are human too.
Max visits Bigger in prison the day he’s scheduled to die. Bigger says that he wishes he had a chance to live, now that he’s seen what life has to offer. But, he’s ready to die. Before Max leaves, Bigger tells him to say goodbye to "Jan." This is the first time he’s called Jan by his first name, indicating that for the first time, he’s embraced Jan’s friendship and recognizes that the two of them are equals. Then Max leaves and Bigger is left alone, waiting to die.