The main character in the book is Jurgis Rudkus, a Lithuanian immigrant trying to make ends meet in Chicago. The book begins with his wife Ona and his wedding feast. He and his family live near the stockyards and meatpacking district where many immigrants, who do not know much English, work. He takes a job at Brown's slaughterhouse. Jurgis 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 substandard slum house, which they cannot afford. The family is eventually evicted after their money is taken.
Jurgis 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 use to stay alive slowly lead to their physical and moral decay. Accidents at work and other events lead the family closer to catastrophe. Jurgis' father dies as a direct result of the unsafe work conditions in the meatpacking plant. One of the children, Kristoforas, dies from food poisoning. Jonas—the other remaining adult male aside from Jurgis—disappears and is never heard from again. Then an injury results in Jurgis being fired from the meatpacking plant; he later takes a job at Durham's fertilizer plant. The family's breakdown progresses as Jurgis discovers an arrangement in which Ona has traded regular sexual favors to Jurgis' boss in exchange for being allowed to keep her job. In revenge, Jurgis attacks Connor, resulting in his arrest and imprisonment.
After being released from jail, Jurgis finds that his family has been evicted from their house. He finds them staying in a boarding house, where Ona is in labor with her second child. She dies in childbirth at age 18 from blood loss; the infant also dies. Jurgis had lacked the money for a doctor. Soon after, his first child drowns in a muddy street. Jurgis leaves the city and takes up drinking. His brief sojourn as a hobo in the rural United States shows him that no real escape is available—farmers turn their workers away when the harvest is finished.
Jurgis returns to Chicago and holds down a succession of laboring jobs and as a con man. He drifts without direction. He finds out that Marija, Ona's cousin, had become a prostitute to support the family and is now addicted to morphine; Stanislovas, the oldest of the children at the beginning of the novel, had died after getting locked in at work and being eaten alive by rats. One night, he wanders into a lecture being given by a socialist orator, where he finds community and purpose. After a fellow socialist employs him, Jurgis locates his wife's family. Jurgis then resumes his support of his wife's family. The book ends with another socialist rally, which follows some political victories.