In Lynley, England, financial difficulties have forced Victor, Earl of Rhyall and his wife Hilary to open their ancestral estate to tourists. After seeing off their young son and daughter for the week, the couple retires to the mansion’s private rooms, where Hilary conducts a small business raising mushrooms and Victor passes time with his butler, Sellers. Sellers, who is employed primarily to impress the tourists, laments the fact that he is too normal and content to succeed as a novelist, which requires a measure of despair. Later, Hilary reads Victor a line of poetry extolling the passions of spring, which he correctly interprets as an appeal for money for a new spring wardrobe. As groups of tourists begin their circuit through the house, debonair American millionaire Charles Delacro enters the private room where Hilary is working. Although she is at first peeved by his forwardness, Hilary is soon charmed by Charles and, upon hearing that he is an oil tycoon, invites him for a drink. They banter pleasantly, their mutual attraction growing rapidly as they discuss their respective backgrounds. They also playfully exchange cultural stereotypes, Charles guessing that Hilary is a spoiled aristocrat who studied history and Hilary assuming that Charles spends frivolously and eats large steaks. When Charles invites Hilary to meet him for lunch in London, however, she refuses, after which Charles redoubles his efforts, and manages to steal a kiss. Flustered, Hilary asks him to leave, but when he stops to take her photograph they are discovered by Victor, who immediately deduces that Charles is a romantic rival and invites him to talk. Hilary watches, her discomfort growing, as Victor and Charles exchange veiled verbal barbs, and when Victor steps away briefly, Hilary begs Charles to leave. Over the next few days, Victor notes that Hilary is increasingly absentminded, and is not surprised when she suddenly makes an appointment to have her hair styled in London. Although he realizes that she is going to rendezvous with Charles, Victor encourages her to go, hoping that she will soon tire of her new interest. Hilary is supposed to stay with her flamboyant friend Hattie Durrant, but after Charles finds Hilary, having called all the city salons to locate her appointment, she spends the next few nights at his hotel. Although Hilary tries to resist Charles, the romance of their illicit affair enchants her, and she begins to fall in love. Meanwhile, Victor waits at home, where he is soon visited by Hattie, who was once his girl friend and now finds mischievous pleasure in divulging the details of Hilary’s affair. In response to Hattie’s questioning, Victor admits that he is afraid to lose his wife but does not want her to return to him out of guilt. To her charge that he has had numerous affairs, Victor insists that those do not count, although he now refuses to sleep with Hattie. At dinner, Victor formulates a plan to win Hilary back by convincing her that she does not really love Charles. To this end, he calls Charles in London and invites him to visit over the weekend, both men pretending that Victor does not know Hilary is with Charles at that very moment. When Charles and Hilary arrive in Lynley, everyone acts as if nothing is amiss, but Victor continually irks Hilary with intimations of her infidelity. Hilary tries to hide the fact that Charles has given her a mink coat, not realizing that Hattie has already revealed the gift to Victor. Although Hilary is tense, the others seem to be enjoying the unspoken tension and acerbic comments, and she complains to Hattie that Victor does not seem to be jealous. At night, Victor finally confronts Charles, insisting that they compete in a duel for Hilary’s love. With Sellers acting as Charles’ second, the two men exchange gunfire, and Victor is hit in the arm. Hilary and Hattie hear the shots and run downstairs, where Hilary insists that Charles leave to fetch the doctor. While she ministers to Victor, Hilary explains that while one part of her is enjoying a romantic interlude, the other still loves him and their life together. Victor discusses infidelity with great practicality, stating that just because one marriage vow is broken does not necessitate the destruction of the entire marriage. Although Hilary mentions the attraction of the jet-set life that Charles offers, she is moved by Victor’s declaration that he will love and cherish her despite her impropriety. He offends her, however, by offering to let her go away with Charles until the American is “out of her system,” which Hilary sees as a “loanout.” Just then, Charles returns, and Hilary indicates that she will stay with Victor by reciting a story about their daughter, who rejected one doll in favor of a newer one, but in the end preferred the old, familiar one. Charles, who deliberately tried to miss when he shot at Victor, suddenly realizes that Victor arranged to be shot to impress Hilary. Victor then confesses that he ordered Sellers to shoot him in secret, knowing Charles would miss and that Hilary would appreciate his willingness to be wounded for her. Hilary is distracted from this revelation by Hattie, who has shown up wearing Hilary’s new mink coat, but once Hilary wrests it off of her, she gives it back to Hattie cheerfully. As Sellers eagerly applies his new experiences to his novel, Victor and Hilary see Charles and Hattie off and prepare to welcome back their children.