British parents try to prepare their Americanized daughter for her social debut.

In London, Lord James Broadbent and his wife, Lady Sheila, look forward to the arrival of Jane, Jimmy's seventeen-year-old American daughter from his first marriage. Jane and Sheila take to each other immediately, but their meeting at the airport is interrupted by Sheila's second cousin, the brassy Mabel Claremont and her daughter Clarissa. Mabel presses Sheila and Jimmy into giving her and Clarissa a ride into town and then chats nonstop about the opening of the debutante season. Clarissa asks if she might show Jane the changing of the royal palace guards, but when the girls are alone, Clarissa admits that she has a crush on royal guard David Fenner. Later over tea, Jane inquires about the "season" and Clarissa explains that every year, girls of seventeen are launched into society by their parents who throw a lavish ball, which, in turn, secures invitations to all the other balls. When the girls arrive at the Broadbents' apartment, Mabel laments that Jane will not be partaking in the coming festivities, but Sheila startles everyone with her announcement that she arranged Jane's coming out long ago. Jane is dismayed and although Jimmy realizes that Sheila has made the decision on the spur of the moment in reaction to Mabel's boasting, he goes along uneasily. A few nights later, Jane attends her first ball with Sheila and Jimmy, and Clarissa introduces her to the pompous David Fenner. When David asks Jane to dance, Jimmy remains in the bar where he meets young American musician David Parkson, who plays drums with the dance orchestra. Later, Jane complains to Sheila that all the young men dance too formally and that she believes dancing should be wild and free, like that of African natives. Jimmy presents David Parkson to Jane, but after the two leave to go dancing, Mabel warns Sheila that David is part-Italian and therefore untrustworthy. Sheila grows alarmed when Mabel then reveals several well-known sources have linked David to a scandal with a debutante the previous year. The next day, Jane meets David Parkson alone at a café at his invitation. After Jane admits that she has never dined alone with a man before, David tells her that although he is departing for a three-week stay in Italy to care for a sick uncle, he would like to see her upon his return. Over the next few weeks, Jane and her parents attend fancy balls nightly, which begins to exhaust Jimmy. As Jane's own ball looms, she looks forward to David Parkson's return. Meanwhile, Sheila expresses her grave concern to Jimmy about Jane's apparent lack of interest in any of the young men at the parties. Faced with another dinner invitation and no escort for Jane, Sheila impulsively telephones Mabel to ask for David Fenner's number. Suspicious of Sheila's motives, Mabel gives her David Parkson's number instead. Having just returned from Italy, David is grateful for the invitation and accepts. Moments later, David Fenner telephones to invite Jane to dine alone. Believing she has just spoken with him, Sheila advises David that it would be best if they all dined together at a fashionable restaurant. That evening when David Fenner arrives at the restaurant, Clarissa is pleased, while Jane remains indifferent. Jimmy runs into David Parkson in the men's room, but does not recognize him. Although puzzled by Jimmy's behavior, David follows him back to the table where Jane lights up upon seeing him. Sheila is confused when David Parkson thanks her for the invitation and becomes uneasy when he then describes his enthusiasm for native dancing. Later on the dance floor, Jane and David Parkson realize Sheila's mix-up, but are happy to see each other again. While they arrange to go to a nightclub following the ball, Clarissa confronts David Fenner about continually flirting with Jane. At the ball later, fearful that Jane is attracted to David Parkson, Sheila orders Jimmy to help watch over her. While waiting for David Parkson, Jane is pursued by David Fenner, who attempts to kiss her on the patio. Escaping David Fenner, Sheila and Jimmy, Jane slips away with David Parkson to a nightclub. Upon returning home at five in the morning, Sheila is scandalized to find that Jane has not yet returned, but Jimmy remains unruffled. When the young couple arrive moments later, Sheila insists that she and Jimmy pretend to have retired, but the pair eavesdrop until Jane discovers them and pleads for them to leave. When they are alone, Jane asks David about his relationship with other girls, then kisses him. After Jimmy reappears and David takes his leave, Jane joins Jimmy in the kitchen and asks her father about his first experience with love. Once Jimmy retires, David slips back in the apartment to return Jane's key and runs into Jane. Jane declares her love for him, and David apologetically reveals that his uncle's recent death makes him the new Duke of Positano. When Sheila catches the two embracing, she demands that Jimmy throw David out. Ordering Sheila away to spare her from the violence, Jimmy pretends to thrash David, who informs him that he would like to marry Jane and explains the confusion over his reputation was actually a mix-up with David Fenner. Later that morning, David Fenner arrives to propose to Jane, who rejects him to Sheila's dismay. Sheila tearfully insists that she only wanted the best for Jane and pleads with her not to see David Parkson. Having read about David Parkson's inheritance and title in the paper, Jimmy suggests that they invite the Duke of Positano to Jane's ball that evening. That night, Clarissa arrives with David Fenner. When the Duke is announced, Sheila is amazed to recognize David Parkson, then, seeing Jane's happy expression, realizes that all has turned out for the best after all.