Emilio drives away in a stolen vehicle until it breaks down. He has it brought to Guglielmo Aniello, a skilled mechanic who needs to replace the ignition coil. While he works, Emilio recognizes Rosa Carrisi, his ex-fiancée, and explains that after leaving her he traveled to the United States and then returned to Europe before World War II. After Emilio leaves, Guglielmo reads in the newspaper that the car had been stolen in Posillipo. He goes to the police headquarters to report the robbery, where he identifies a man resembling Emilio. The real Emilio is not arrested and meets with Rosa after she drops her son Tonino Aniello at school. Rosa condemns Emilio for the robbery and asks to be left alone.
At a pyrotechnics festival, Emilio encounters Rosa again, convinced that fate has led him to her. The next morning, Guglielmo invites Emilio for coffee to discuss plans to expand his mechanic shop. Rosa disagrees, and Emilio leaves. Shortly after, Rosa confronts Emilio at his residential hotel and threatens to reveal their relationship to her husband. Regardless, Emilio expresses he is still in love with her. Rosa pleads again to be left alone, and returns home frustrated. Perplexed by his wife's behavior, Guglielmo follows his mother's advice and takes Angela Aniello to Naples for her birthday. Suddenly, Emilio arrives and sits near her at a table. As Rosa and Emilio reminisce their past romance, Tonino becomes troubled when he sees Emilio tightly holding his mother's hand.
Back at home, Tonino disrespects his mother, in which Guglielmo questions his son's behavior. The next morning, Rosa is handed a blackmail letter from Emilio, in which he threatens to reveal their relationship to Guglielmo if she does not choose him. As Rosa prepares to leave, Tonino tries to block his mother, but she shoves him aside. Angela, Rosa and Guglielmo's youngest daughter, alerts her father about Tonino's fight with Rosa and informs him about the letter. Guglielmo finds the letter in their cabinet and rushes to find his wife.
Rosa arrives at Emilio's hotel suite and pulls a handgun, but refuses to shoot him. Emilio forces himself on Rosa until Guglielmo arrives. He locks Rosa outside the door and shoots Emilio. Guglielmo sails for America, and Rosa leaves her children to Anna Aniello, Guglielmo's mother. By Christmastime, Rosa has grown desperate for her children and is allowed to see Angela in her bedroom. Meanwhile, Guglielmo has grown homesick and is arrested by authorities to be sent back to Italy to stand trial.
At an attorney's office, Rosa learns Guglielmo faces thirty years in prison for premeditated murder, but affirms she is innocent of adultery. She hands the attorney the blackmail letter, to which Guglielmo's killing can be considered a crime of passion if Rosa confesses to adultery. The trial proceeds and Guglielmo is found not guilty, having acted in self-defense. With her reputation damaged, Rosa considers suicide but Guglielmo prevents her. He has learned from the attorney that Rosa has always been faithful. The two reunite with their children.
