When Philadelphia lawyer Michael Hamilton travels to Naples, Italy to settle the affairs of his late, estranged brother Joseph, he cynically assumes that all Italians are interested only in bilking tourists. Mike’s suspicions are heightened by his glib Italian lawyer, Mario Vitale, who reveals that the profligate Joe died with his wife in a boating accident. Upon Mike’s retort that Joe’s wife is alive and well in Philadelphia, Mario states that Joe and his common-law Italian wife left behind an eight-year-old son, Nando, who is being reared by his aunt, Lucia Curcio. After Mike grumpily protests that he needs proof that Nando is his nephew, Mario takes him to a street festival and introduces him to a regally costumed Lucia. Lucia is furious that Mike may have come to take away Nando and dismisses him after stating that they live happily on the nearby isle of Capri. Undeterred, Mike travels to Capri, where he inadvertently meets Nando when he requests a guide to Lucia's villa. Mike does not introduce himself at first, but after noting Nando’s resemblance to Joe and his habit of whistling at pretty girls, shakes the enterprising boy’s hand and states “welcome to the family.” Upon entering Nando and Lucia’s ancient yet homey villa, Mike is bemused by Nando’s self-sufficiency as the boy cooks dinner. Lucia is upset by Mike’s surprise visit and claims that because their real villa burned down, they are living in the servants’ quarters. As her lie unravels, Lucia rails against judgmental Americans, but Mike disarms her with his quips. He then reveals that because Joe wrote to him only when he wanted money, he did not know about Joe’s death for more than a year. He also asks what happened to the $14,000 he had sent to Joe over the years, and Lucia and Nando reply that Joe built a fireworks business, but because his fireworks were so specialized and expensive, he died bankrupt. Lucia, who is devoted to Nando despite her lackadaisical approach to parenting, is relieved when Mike asserts that he has no desire to take the boy and instead promises to send money for his care. Although Nando is dismayed by his uncle’s lack of interest in him, Mike departs, but discovers that he has missed the last boat back to Naples. Kept awake by the music playing in the palazzo under his hotel room window, Mike wanders down to inspect the nightlife. He is shocked to find Nando handing out flyers featuring a scantily clad Lucia, who performs at a local nightclub. After sending Nando home, Mike goes to the club, and although he enjoys Lucia’s performance, he remains suspicious of her. Mike gives a waiter half of a large banknote, along with his room key, to pass along to Lucia, but instructs him not to tell her who sent them. Mike’s fears that Lucia’s affections are for sale appear to be realized when he finds her reclining on his hotel bed, but she laughingly states that the waiter told her who he was. Not appreciating her joke, Mike insists that she is a terrible parent to Nando, who does not even attend school. After Mike announces that he will be sending Nando to the American school in Rome, Lucia storms out. When she returns home, she yells at Nando that he must go to school and start behaving properly. Nando replies angrily but the pair soon wind up crying in each other’s arms. The next day, Mike comes for Nando, but when Lucia declares that Mike is trying to kidnap the boy, her neighbors disparage him and all Americans. Forced to leave, Mike returns to the hotel. Later, he is visited by Nando, who states that without him to look after her, the impulsive Lucia will get into trouble. Mike tries to impress upon the boy the importance of a good education, but Nando describes with derision how Americans treat Italians like his mother, who did not even get a wedding ring. Soon after, Lucia receives notice that Mike is seeking custody of Nando. That night, Mike shoots off the rest of Joe’s fireworks in hopes of drawing out Nando. His plan succeeds as the little boy joins him, and soon Nando spends his days showing Mike around Capri. One afternoon, Mike meets with Mario to discuss their legal strategy, and Mario, who secretly hopes to play matchmaker, tells him that Lucia “bears a great affection” for him, and suggests he settle the problem without resorting to the courts. After Mike leaves, Lucia confronts Mario, who tells her that Mike bears a great affection for her, and that she can charm him into letting her keep Nando. That night, Mike visits Lucia at the club and they dance for hours. As they spend more time together, Mike relaxes, dressing more casually and acting less formally. One evening, at another street festival, as Nando and Mike watch Lucia in the procession, Nando asks when Mike is going to marry Lucia. Mike tries to explain that he has other obligations and merely has been having fun with Lucia, and the disillusioned Nando runs away. Meanwhile, Renzo, Lucia’s guitarist, tells her that he has arranged for them to tour Italy together. They are interrupted by Mike, who confesses to Lucia that Nando ran off after their argument. Mike also tells Lucia what they argued about, and although Lucia pretends that she never took their relationship seriously, she is deeply wounded. Lucia declares that she was leading Mike on to keep Nando, and Mike retorts that he will see her in court. Later, in the courtroom, Mario does his best to influence the judges in Lucia’s favor. Mike then speaks, declaring that he only wants Nando to have the best opportunities life can offer. Lucia wins the case but, moved by Mike’s dreams for Nando, tells her nephew that she is going to tour with Renzo and that he would get in the way if he came along. Crushed by her rejection, Nando gets drunk and goes to Mike’s hotel, where he tells his uncle that he wants to be an “Americano.” Later, at the train station, Nando reveals that Lucia was crying when she told him she did not want him anymore, and Mike deduces the sacrifice Lucia is making. Mike then gives Nando money to return to Capri and boards the train. When he enters his compartment, however, the boorish manners of three American tourists make him realize that he belongs in Italy. Jumping off the train, Mike joins the ecstatic Nando on the platform. They then return to Capri, and after Mike gives Lucia a bouquet of balloons, the new family walks off together.