The main character in the book is Jurgis Rudkus, a Lithuanian immigrant trying to make ends meet in Chicago. The book begins with his and Ona's wedding feast. He and his family live near the stockyards and meatpacking district, where many immigrants work who don't know much English. He takes a job at Brown's slaughterhouse. Rudkus had thought the US would offer more freedom, but he finds working conditions harsh. He and his young wife struggle to survive. They fall deeply into debt and are prey to con men. Hoping to buy a house, they exhaust their savings on the down-payment for a sub-standard slum house, which they cannot afford. The family is evicted after their money is taken.
Rudkus had expected to support his wife and other relatives, but eventually all – the women, children, and his sick father – seek work to survive. As the novel progresses, the jobs and means the family uses to stay alive slowly lead to their physical and moral decay. Accidents at work and other events lead the family closer to catastrophe. One injury results in Rudkus being fired; he later takes a job at Durham's fertilizer plant. The family's hardships accumulate as Ona confesses that her boss, Connor, had raped her, and made her job dependent on her giving him sexual favors. In revenge, Rudkus attacks Connor, resulting in his arrest and imprisonment.
After being released from jail, Rudkus finds that his family has been evicted from their house. He finds them staying with relatives, where Ona is in labor with her second child. She dies in childbirth at age eighteen from blood loss. Rudkus had lacked the money for a doctor. Soon after, his first child drowns in a muddy street. Rudkus leaves the city and takes up drinking. His brief sojourn as a hobo in rural United States shows him that there is really no escape – farmers turn their workers away when the harvest is finished.
Rudkus returns to Chicago and holds down a succession of laboring jobs and as a con-man. He drifts without direction. One night, he wanders into a lecture being given by a Socialist orator, where he finds community and purpose. A fellow socialist employs him, and he resumes his support of his wife's family, although some of them are damaged beyond repair. The book ends with another socialist rally, which follows some political victories.