In Boston, psychologist Robert Dean and his wife Mary say goodbye to their eldest daughter Meg, who is joining a four week tour of South America before returning to college. On the last week of the tour, the Deans receive a telegram from Meg, notifying them that she plans to stay in São Paulo for six more weeks to take a course from famed architect Eduardo Barroso. Alarmed, Robert immediately books seats for the family on the next flight to São Paulo, prompting their wise-cracking, jive-talking younger daughter Betsy to complain that the trip will ruin her summer vacation. At the São Paulo airport, the Deans are met by Meg, attired in a sophisticated dress, and the suave Eduardo, who is her father's age. Robert's worst suspicions are confirmed when Meg ebulliently announces that Eduardo has arranged a one-year scholarship for her to study sculpture in São Paulo. Meg, clearly in awe of Eduardo, takes her family on a pilgrimage to the great architect's buildings. One day, while the Deans are taking an air tour on a sightseeing plane, their craft is forced down to refuel at the U.S. Air Force Missile Tracking Station. Once on the ground, Betsy is ogled by the women-starved servicemen. Smitten by love at first sight, Sgt. Paul Gattling follows Betsy back to the aircraft, kisses her and promises to visit in São Paulo. Back in the city, Robert goes to the women's residence in which Meg is staying and sees her dash out the door and jump into a taxi. Robert follows, and when he spots Eduardo speeding to meet her, he turns back, disheartened. At the Barroso villa, Eduardo's rebellious son, painter Carlos Barroso, asks Meg to marry him. When Carlos refuses to meet Meg's "bourgeois" family, however, Eduardo wonders if she would wed against her parents' wishes. At the Deans' hotel later, Meg introduces her family to Carlos, who denounces all materialistic values, including the desire to earn a living. Shocked by the bohemian Carlos, Robert makes arrangements for the family to fly to Rio de Janeiro the next day. Soon after, Paul appears at the hotel, AWOL, to see Betsy. Upon returning to base, Paul is demoted from sergeant, but then pleads for a leave due to extenuating circumstances, his love for Betsy. In Rio, Robert announces that they are flying to Lima, Peru the next day to see the bullfights. Feeling betrayed by her father for forcing her to leave Brazil, Meg phones Eduardo to ask him to tell Carlos goodbye. On the phone, Carlos berates Meg for being a little girl who leads her parents' life. Nevertheless, Eduardo and Carlos fly to Lima to rescue Meg and then proceed to the bull ring. There, Robert, whose lifelong dream was to attend a bullfight, is repulsed by the brutality he sees in the ring and runs from the stands back to his hotel. Spotting each other from across the crowd, Carlos and Meg embrace. Back at the hotel, Robert is worrying about his daughters when Paul knocks at the door, famished from his quest to find Betsy. Soon after, Betsy arrives, but when Paul proposes to her, she declares that she is not yet ready to marry. Soon after, Eduardo, Carlos and Meg come to the hotel, and Eduardo informs the Deans that he has purchased three tickets to fly to São Paulo that night. When Meg ardently begs for her father's blessing, Robert coldly bids her farewell. Later, at a nightclub, Robert becomes drunk and when Paul eagerly tells him that Betsy has agreed to marry him, he withholds his permission. After spraying red wine all over his shirt, Robert goes back to the hotel to change his clothes. On the way, he disrupts a street artist in the middle of painting a portrait, prompting the angry artist to chase Robert and knock him unconscious. While he is passed out on the street, Robert is mistaken for a member of a Spanish tourist group and carried unconscious back to the group's waiting plane. Upon awakening, Robert discovers that the plane is bound for Madrid, and convinces the pilot to drop him off in Trinidad. In São Paulo, the clerk at Meg's residence hands her a message to call an international number. After she dials, Robert answers from Trinidad and admonishes her to lead her own life. When he asks if he can attend her wedding, Meg confides that she has some misgivings about Carlos. Soon after, Betsy, Paul and Mary arrive in Trinidad and Robert sheepishly admits that he, too, is fallible. Robert then declares that Betsy, being of age, is capable of reaching her own decision about marriage.