A middle-aged lawyer named Alfieri introduces the audience to the Brooklyn neighborhood of Red Hook in the 1950s, populated mostly by Italian-American immigrants. Alfieri says that the people of the neighborhood are “quite American,” and that “justice is very important here.” Alfieri points out Eddie Carbone, a longshoreman who works on the docks. Eddie is returning home from work, and sees his niece Catherine, whom he looks after like a daughter. He tells his wife Beatrice that her cousins from Italy have arrived. (They are sneaking into the country as illegal immigrants and will stay at Eddie’s apartment.) At dinner, Catherine tells Eddie that she has gotten a job as a typist, but Eddie is reluctant to let her go to the job. Beatrice chides him, and he relents and lets her accept the job. He says that she will eventually move out and see him less and less often, and jokes that he “never figured on” Catherine growing up. Beatrice’s cousins, Marco and Rodolpho, arrive at the apartment. They thank Eddie for allowing them to stay at his home, and are excited at the prospect of work. They can find no jobs in their hometown in Italy, and have come to America to work and send money back to their families. Catherine begins to be fascinated by Rodolpho, who says that he wants to stay in the United States and become a rich American. He sings a song called “Paper Doll” for Catherine until Eddie tells him to be quiet, so the neighbors don’t realize anyone is staying with them and report them to the Immigration Bureau.
Alfieri tells the audience that as time went on with Rodolpho and Marco living in the apartment, “there was a trouble that would not go away.” A few weeks after their arrival, Eddie waits anxiously at night for Rodolpho and Catherine to return from a movie. He tells Beatrice that Rodolpho is “weird,” and sings so much that the other longshoremen have nicknamed him Paper Doll. Eddie talks to two neighbors, Mike and Louis, who laugh about Rodolpho and call him “humorous,” though they seem to imply something more. Rodolpho and Catherine enter, and Eddie talks to Catherine alone. He warns her that Rodolpho doesn’t respect her and just wants to use her to get an American passport through marriage. Catherine is upset and insists that Rodolpho really loves her. Beatrice talks to Catherine and encourages her to make her own decisions, and to stop acting like a young child in front of Eddie.
Alfieri tells the audience that Eddie then came to see him in his office. We see Eddie go to Alfieri’s office and ask if there’s anything he can do, legally speaking, to keep Rodolpho and Catherine apart. Alfieri says that Rodolpho has done nothing illegal, but Eddie continually insists that Rodolpho “ain’t right,” seemingly questioning his masculinity and heterosexuality. Alfieri advises Eddie to let Catherine be with Rodolpho, and says that sometimes love “goes where it musn’t.” He tells Eddie that sometimes “there is too much love for the daughter, there is too much love for the niece.” Eddie leaves the office and Alfieri tells the audience that he knew something bad was going to happen, but was powerless to stop it.
Back at Eddie’s apartment, Eddie confronts Rodolpho about going out with Catherine without asking his permission first. Rodolpho assures him that he respects Catherine. Catherine puts on a record of the song “Paper Doll,” and she and Rodolpho dance. Eddie asks if Rodolpho has ever boxed, and offers to teach him. The two spar, and Eddie punches Rodolpho directly in the face. Marco is troubled by this, and asks Eddie if he can lift a chair with one hand. He can’t, and then Marco lifts the chair until he his holding it over his head, facing Eddie almost threateningly.
In Act Two, the play jumps forward to the 23rd of December. Catherine and Rodolpho are alone in Eddie’s apartment, and Catherine asks if he would be willing to live with her in Italy. He says that it would be foolish to return to Italy where there are no jobs, but promises that he is not interested in Catherine merely in order to become an American citizen. Rodolpho asks why Catherine seems so frightened of Eddie, and Catherine says that he has been kind to her and she doesn’t want to upset him. Rodolpho tells Catherine that she has to leave Eddie, and she starts to cry. They go into a bedroom. Eddie arrives at the apartment and is furious when he sees Rodolpho and Catherine come out of the same bedroom. He tells Rodolpho to pack up and leave, and then grabs Catherine and kisses her. Rodolpho is shocked and attacks Eddie, and Eddie pins his arms back and kisses him forcefully.
Alfieri tells the audience that he next saw Eddie on the 27th. Eddie comes into Alfieri’s office and asks if he can call the police or do something. He says that Rodolpho “ain’t right” and didn’t try to break free of his kiss. Alfieri says that there is nothing Eddie can legally do and that Catherine is free to make her own decisions. Frustrated, Eddie leaves Alfieri’s office and goes to a payphone. He calls the Immigration Bureau and reports Marco and Rodolpho. When he gets home, Beatrice has moved Rodolpho and Marco into an apartment upstairs with two other illegal immigrants living with the Lipari family. Eddie is upset with Beatrice and says that she doesn’t respect him. He tells her that he doesn’t want to talk about “what I feel like doin’ in the bed and what I don’t feel like doin’,” and continues to say that Rodolpho “ain’t right.” Beatrice tells Eddie that Rodolpho and Catherine are getting married in a week. Catherine enters and asks Eddie to attend the wedding. Eddie tells her that he’ll let her go out at night and meet men, just as long as she doesn’t marry Rodolpho. Catherine tells him that she loves Rodolpho.
Two officers from the Immigration Bureau arrive and search Eddie’s apartment. Not finding anyone, they decide to search the rest of the building. They find Rodolpho, Marco, and the other two illegal immigrants. Beatrice asks Eddie, “My God, what did you do?” as Catherine tries to persuade the officers that Rodolpho is American. The officers take the immigrants outside, and Marco shouts out that Eddie has betrayed him. Eddie claims this is false, but Lipari, Mike, and Louis ignore and shun him. Eddie shouts that he will kill Marco if he doesn’t take back his accusation.
Later, at a prison, Alfieri tries to convince Marco to promise not to take revenge on Eddie by killing him, so that he can be freed on bail. Marco says that it would be unjust not to take revenge, but grudgingly agrees to the promise. The play then jumps to the day of Catherine’s wedding. At Eddie’s apartment, Beatrice tries to convince Eddie to attend. Eddie tells her that he wants her respect as a wife and that he won’t go to the wedding unless Marco apologizes to him. Catherine is upset and calls Eddie a rat. Rodolpho enters, apologizes to Eddie for having disrespected him, and says that Marco is coming. Eddie says he wants Marco to apologize to him in front of the whole neighborhood. Beatrice says an apology is not what he really wants, and says that she knows what he wants and “you can never have her!” Catherine and Eddie are both shocked at this. Marco arrives outside the apartment, and Eddie goes to meet him. He calls Marco a liar and tells him to apologize. Marco hits Eddie and calls him an animal. The two fight and Eddie pulls out a knife. He lunges at Marco but Marco grabs him and turns the knife on Eddie, stabbing him. Eddie falls over and dies in Beatrice’s arms. Alfieri closes the play by telling the audience that although Eddie behaved wrongly, he was still a pure person, “not purely good, but himself purely.” He says he mourns him and regards him “with a certain . . . alarm.”