The novel opens as Bigger Thomas, the protagonist, faces down and fights a huge rat that has invaded the Thomas’ one-room apartment. We are instantly assailed with the family’s poverty and lack of options.
During the day, as Bigger waits to see a wealthy white man for a job as chauffeur, he considers robbing a white-owned business with his buddies. All of them are afraid to rob a white man, though nobody says so. Finally, Bigger threatens one of his friends in order to escape doing it. That afternoon, he goes to the Daltons’ house and gets the chauffeuring job. His initial encounter with Mary Dalton, the rebellious daughter, makes him uncomfortable and worried that he’ll lose his job because she keeps talking to him about "unions." His first task is to drive her to the university that night. Instead, she directs him to a building where she meets her boyfriend, a Communist named Jan Erlone. The two young people drive Bigger around, trying to befriend him, but ultimately making him feel ashamed and angry to be black.
Late that night, Bigger has to help Mary up to her room because she’s too drunk to stand up by herself. She comes on to him when he is bringing her to her room. Alone in the room with her, he’s aroused. But at that moment, Mary’s blind mother, Mrs. Dalton, comes to the door to see if her daughter has made it home safely. Afraid that she’ll catch him in the room alone with a white woman, Bigger covers Mary’s head with a pillow to keep her silent and accidentally smothers her to death. Now afraid that he’ll be charged with murder, Bigger burns Mary’s body in the basement furnace to hide what he has done. He has to cut her head off with a hatchet to fit her body in the furnace but finally, he manages to get it done. He returns to his home on the South Side of Chicago to catch a couple hours of sleep. Bigger’s act fills him with a sense of purpose for the first time in his life. He feels like he’s actually done something that nobody else made him do, so he commits himself to his course of action.
Back at the Daltons’ house, Mrs. Dalton is worried about where her daughter is. Though Mary was supposed to take a train to Detroit that day, Mrs. Dalton has noticed that she’s left many of her new clothes behind, which her mother finds strange. Bigger suggests that the last time he saw Mary, she was with Jan. Mrs. Dalton sends Bigger home for the day and Bigger visits his girlfriend, Bessie. Though Bessie is clearly reluctant to participate, Bigger makes plans to write a kidnap note in order to benefit financially from Mary’s disappearance. Bessie suspects he’s done something to the girl.
Bigger goes back to the Daltons’ house, where Mr. Dalton has hired a private detective. Britten, the detective, questions Bigger and Bigger makes his story point towards Jan. Britten eventually finds Jan and questions them together. Jan wonders why Bigger is lying and if he was told to lie. Later, Jan confronts Bigger out on the sidewalk and Bigger threatens him with a gun until he runs away.
Bigger writes his kidnap note, slips it under the door, then returns to his room at the Daltons. Mr. Dalton calls the police, who arrives with the media in tow. Bigger keeps wondering if he should leave but he’s too anxious to find out what happens. He still thinks he might get his hands on the money. When he’s told to empty the ashes in the furnace to get the fire going again, he’s nervous and fills the room with smoke. A journalist takes over for him and soon finds the remains of Mary’s body. Bigger flees through his bedroom window and goes to find Bessie.
He convinces Bessie they have to leave together because she knows too much. Once he gets her alone, however, he rapes her. Afraid she’ll give him away whether he takes her with him or leaves her behind, he hits her with a brick, then throws her into an airshaft in an abandoned building. So now Bigger has murdered two women. He also forgets that Bessie had been carrying the money he stole from Mary.
The city starts a massive manhunt. Bigger is eventually cornered, and though he never submits, police tactics are too powerful for him and he finally gets caught. In jail, Bigger refuses to eat or drink or talk to anyone. Jan comes to visit and says he understands now why Bigger acted the way he had. He has brought a Communist lawyer with him, Mr. Max, who will represent Bigger. Max and Bigger spend hours together. Bigger finally begins to confide in Max, telling him how he lacked choices all his life as young black man and how there really was no future for him. As Bigger begins to see the mob mentality outside the doors of the jailhouse, he realizes he’s a dead man if he ever finds himself outside the prison walls without police protection.
When Max defends Bigger at his trial, he claims essentially that American society boxes black men and women in. He argues that society gives them no options in life and denies them the basic right of all humans – to fulfill their destiny in relationship to the measure of intelligence and talents they were born with. This creates anger, shame, and fear, and it boils over into crime, such as Mary’s murder. He encourages the judge to give Bigger life in jail instead of the death sentence. But the judge concurs with the prosecution and Bigger is sentenced to the electric chair.
The day he is going to die, Bigger and Max have another conversation. Bigger talks about all that he’s learned about himself and about humanity; he wishes he had a chance to experience life with the knowledge he’s gained. When Max gets up to go, Bigger asks him to tell Jan goodbye. (This is the first time he’s called him Jan instead of "Mr." Jan.) Max says he will. Bigger is left alone, waiting for the moment the guards take him in to die.