In the French Riviera town of Beaumont-sur-Mer, British confidence artist Lawrence Jamieson pretends he is an urbane prince in exile. At the casino of the Grand Hotel, Lawrence meets his associate, Inspector Andre, Beaumont-sur-Mer’s police chief, and learns of a new mark: Fanny Eubanks from Omaha, Nebraska. Lawrence joins Fanny at the roulette table. Andre approaches and addresses Lawrence as “Your Highness,” and Lawrence leaves. Believing Lawrence to be royalty, Fanny approaches Andre, who tells her Lawrence is a prince in need of money to fund his people’s fight for freedom. Intrigued, Fanny finds Lawrence and offers to assist him. Later in her bedroom, Fanny gives Lawrence her diamond earrings. The following day, Lawrence divides the money from selling Fanny’s earrings with Andre, and his manservant, Arthur. After traveling to Zurich, Switzerland, to deposit his money, Lawrence returns to Beaumont-sur-Mer by train. In the dining car, Lawrence sees American Freddy Benson join a woman at another table. Freddy tells her his grandmother is ill and he needs to save money. Moved by his story, the woman offers to buy his meal. Watching the interaction, Lawrence concludes Freddy is a con artist. Later, Freddy barges into Lawrence’s compartment. After Freddy mentions he is going to Beaumont-sur-Mer, Lawrence tells him the Italian Riviera’s Portofino is a richer place. However, Freddy is not persuaded. Lawrence excuses himself and calls Andre. Arriving at the station, a beautiful Italian woman, Marion, enters the compartment, saying she is traveling to Portofino. Freddy decides to stay on the train. Lawrence finds Andre on the platform and thanks him for instructing Marion to tempt Freddy to Portofino. The next day, Andre reads a newspaper article about “The Jackal,” an American con artist working in Western Europe. Andre and Lawrence assume Freddy to be “The Jackal.” Andre informs Lawrence that Krista Knudsen, a wealthy young widow is scheduled to arrive in Beaumont-sur-Mer. Just then, Krista drives by with Freddy Benson in her white Ferrari. Later, Freddy takes Krista’s Ferrari around town and spends the money she gave him for his grandmother. However, Andre and Krista follow him, and seeing Freddy’s deceit, Krista files a complaint. Andre arrests Freddy and puts him in jail. Remembering Lawrence from the train, Freddy telephones him. Lawrence tells Freddy he needs five thousand dollars to bribe Andre. After Freddy promises to get the money, Lawrence and Andre escort him to the Beaumont-sur-Mer airport. From the airplane, Fanny Eubanks sees Lawrence shaking Freddy’s hand. During the flight, Fanny approaches Freddy and tells him about her relationship with the prince. After hearing Fanny’s story, Freddy realizes that Lawrence conned her. The next day, Freddy arrives unannounced at Lawrence’s villa, wanting to be mentored in the con man’s methods. To keep him quiet, Lawrence agrees. He includes Freddy in the exiled prince charade as “Ruprecht,” the prince’s simple-minded brother. As Ruprecht, Freddy scares away the rich women Lawrence promises to marry after stealing their money. A month later, Lawrence withholds Freddy’s share of the money, stating he would only spend it foolishly. Frustrated, Freddy leaves. However, Lawrence discovers Freddy has not left Beaumont-sur-Mer and insists they cannot work in the same place. Freddy suggests a bet: the first man to con the most money from a woman stays. Lawrence agrees. At the Grand Hotel, they learn that Janet Colgate, the United States “Soap Queen,” just checked-in. The men agree on Janet being the mark, and tricking her out of fifty thousand dollars. Later at the hotel casino, Lawrence sits next to Janet at the roulette table. Arriving in a wheelchair and formal military uniform, Freddy asks the dealer how much his military medal is worth. When told the medal cannot be cashed in, Freddy leaves in tears. Concerned, Janet follows him. Freddy tells her he is on “Mental Trauma Leave” because he lost the feeling in his legs, after his fiancée cheated on him with a dance competition host. He continues saying only Dr. Emil Schaffhausen, a psychiatrist in Liechtenstein, can cure him, but the price for the treatment would be fifty thousand dollars. Freddy further convinces her by pretending to have a panic attack while seeing a couple dancing. Janet takes Freddy to her hotel room, promising to write to the Schaffhausen Clinic and pay for his treatment. As they leave, Andre informs Lawrence of Freddy’s story. Leaving Freddy in her room to mail the letter, Janet follows a bellboy paging Dr. Schaffhausen in the lobby and finds Lawrence. After introducing himself as “Dr. Emil Schaffhausen,” Janet pleads Freddy’s case. Lawrence agrees to take Freddy as a patient, if Janet pays the fifty thousand dollars fee directly to him. She agrees and leads Lawrence to her room to meet Freddy. Unable to trick Freddy into moving his legs, Lawrence insists Freddy come to live in his villa for treatment. Before leaving the hotel, Mrs. Reed, a former mark Lawrence conned money from, recognizes Lawrence and calls him “Your Highness.” To fool Janet, Lawrence tells Mrs. Reed he is on an undercover mission. Afterward, Lawrence informs Janet that Mrs. Reed is a former patient suffering from delusions. Throughout the week, Freddy and Lawrence compete for Janet’s attentions and affections to secure her money. At a local dance hall, Lawrence and Janet dance, while Freddy, in his wheelchair, watches. Freddy tells two British sailors that Janet was his girl friend, but Lawrence stole her. When Lawrence kisses Janet, the sailors offer to kidnap Lawrence and send him to Honduras. Later at the Grand Hotel, as Lawrence walks Janet to her room, she tells him she almost has the fifty thousand dollars. Lawrence says he thought she was the “Soap Queen.” However, Janet explains she won a contest for the “United States Soap Queen” from the United States Soap Company, and received a cash prize and European trip. Her winnings will not cover Freddy’s treatment, so she has asked her father to sell her belongings. Driving to the villa, Lawrence tells Freddy the bet is cancelled because Janet has no money. However, Freddy changes the stakes, with the winner being the first to trick Janet into sleeping with him. Lawrence accepts in order to protect Janet from Freddy. The British sailors from the dance hall pull up in a van and abduct Lawrence. As they drive away, Freddy thanks the sailors and returns to the hotel. In her room, Freddy tells Janet he loves her, and proves it by getting out of his wheelchair and walking. Lawrence appears and deems Freddy “cured.” After leaving Janet’s room, Lawrence informs Freddy that the sailors freed him because he is a Royal Navy Volunteer Reserve member, and that Janet will be leaving in the morning. Lawrence leads Freddy to a suite where the British sailors are having a party. Knowing Freddy lied to them, the sailors promise to keep Freddy away from Janet. In the morning at the airport, Janet tells Lawrence she is falling in love with Freddy, but Lawrence insists she must leave and waives the fifty thousand dollars fee. He returns to the hotel and finds Freddy in the sailors’ suite with his hand super-glued to the wall. Lawrence informs Freddy he lost the bet because Janet is gone. Freddy goes to Janet’s hotel room and finds it is empty, but Janet appears, tells Freddy she loves him, and kisses him. Meanwhile, Andre telephones Lawrence to inform him Janet returned to the hotel for Freddy. Later, Janet comes to Lawrence in tears, confessing she slept with Freddy, but afterwards he stole her fifty thousand dollars. Feeling sorry for Janet, Lawrence places fifty thousand dollars of his own money into a satchel and gives it to her. He instructs his manservant, Arthur, to call Andre and have Freddy arrested while he takes Janet to the airport. Before she boards the airplane, Janet returns the satchel, saying she cannot accept Lawrence’s money. As the plane takes off, Andre arrives with Freddy in a bathrobe saying Janet stole his clothes and money. Opening the satchel, Lawrence finds Freddy’s clothes and a note from “The Jackal.” Realizing they have been conned, Freddy is upset, but Lawrence is impressed. A week later at Lawrence’s villa, Freddy prepares to leave Beaumont-sur-Mer. Just then, a group of Greek vacationers arrive, led by Janet in a red wig. Posing as real estate agent “Paula,” Janet introduces her Greek millionaire client to “Chips O’Toole,” the Australian hotel mogul. Playing along, Lawrence answers in an Australian accent. Janet then introduces Freddy as “Randy Bentwick,” Chips’ mute, junior partner. As the millionaire and his friends wander towards the villa, Janet tells Lawrence and Freddy that conning them out of fifty thousand dollars was the most fun she has ever had. The three of them walk to the villa, discussing their next con.