The main character in the story is Eddie Carbone, an Italian American longshoreman, who lives with his wife, Beatrice and his orphaned niece, Catherine. As the play begins, Eddie is protective and kind toward Catherine, although his feelings grow into something more than avuncular as the play develops. His attachment to her is brought into perspective by the arrival from Italy of Beatrice's two cousins, Marco and Rodolpho. They have entered the country illegally, hoping to leave behind hunger and unemployment for a better life in America. Marco is an exceptionally strong man, said by Eddie's friends to be 'a regular bull.' He also has a starving family in Italy (a wife, and 3 sons, one with tuberculosis). Rodolpho is in his late 20's, fair skinned, blond, and unattached. He is unconventional in that he sings (notably 'paper doll'), dances, is good at sewing and dress making and is also a good cook. Catherine soon begins a relationship with Rodolpho.
After three weeks, the pair have been seeing each other, and Eddie sets about pointing out all of Rodolpho's flaws to Catherine and Beatrice. He persistently complains that Rodolpho is "not right," referring to Rodolpho's effeminate qualities, such as sewing, cooking and singing. He is embarrassed by Rodolpho's reputation for singing during work.
When Catherine decides to marry Rodolpho, Eddie becomes desperate and begs his lawyer, Alfieri (who is also the narrator), to help him. However, he is told that the only way the law is able to help him is if he informs the Immigration Bureau of the presence of the two illegal immigrants. Due to his earlier assertion that "it's an honor" to give the men refuge, he refuses to betray them. At home he continues to passively insult Rodolpho, and ends up offering to teach Rodolpho to box, however Eddie uses this opportunity to hit Rodolpho. In retaliation, Marco challenges Eddie to lift a chair from the bottom of its leg, when Eddie fails to do this, Marco picks up the chair with one hand from the bottom of its leg and lifts it above his head. This demonstrates Marco's superior strength and that he will always be watching over Rodolpho, should Eddie harm him.
In the second Act, Eddie catches Rodolpho leaving the bedroom with Catherine. He then sees Alfieri a second time. Eddie ignores his lawyer's advice to let events run their course, and calls the Immigration Bureau. This betrayal proves disastrous: he comes back to learn that Catherine and Rodolpho are engaged, and Beatrice informs him two more illegal immigrants have moved into the upstairs apartment. Suddenly, the Immigration Officers arrive and shortly arrest the four immigrants. As the detainees are being taken from the tenement, Marco breaks free from the group, "dashes into the room" and spits in Eddie's face. This happens inside Eddie's house – however Eddie's rage is such that he follows Marco out into the street. He berates Marco for the insult, failing to notice that the gathering crowd are growing as one to conclude that Eddie is the traitor. This suspicion is confirmed as Marco singles Eddie out as the one who "killed my children."
Rodolpho is allowed to stay in the country due to his marriage, but Marco faces imminent deportation. Reluctantly, he promises Alfieri not to take revenge on Eddie (as is the Sicilian custom) and is let out on bail. In the final scene of the play, Eddie is shown to be furious with his humiliation and refuses to attend the wedding. He rejects Rodolpho's offer to reconcile and refuses to get out of the house when he learns Marco is arriving.
The play ends with a fight between Eddie and Marco, in a street filled with his friends and family. Eddie brandishes a knife and attacks Marco, who turns the blade onto Eddie, killing him. It is not known whether Marco actually intended to stab Eddie, and his reaction is not described. Eddie dies as the curtain falls, calling out to Beatrice.
