Secrets of Monte Carlo

Outside Monte Carlo, a ring of thieves led by the sophisticated Otto Von Herzen steal the jewels of the Rajah of Bandore. As part of an elaborate plan to get the jewels out of the country, Otto's cohort, Stella Strutzenbacher, beguiles an American businessman, Bill Whitfield. At the airport she tricks him into carrying her suitcase, which unknown to him, contains a fake jewel and clothes that were stolen from his hotel room while they were socializing. As he tries to board the airplane, the bag is searched and Stella disappears. Believing they have found the Bandore jewel thief, the police summarily arrest Bill, and airport security is relaxed, which allows Otto to smuggle the real jewels on the plane easily. Stella and the two other thieves, Louis Gunther and Tony Retella, take separate routes, but plan to meet later in Hong Kong. After the police realize that the jewel is counterfeit and that Bill's story checks out, Bill is freed, but the London insurance investigator on the case, Charles Reeves, suspects that the imitation, possibly of Hong Kong origin, might provide a lead to the thieves and decides to travel with Bill to Hong Kong. At the airport, Charles introduces Bill to his sister Susan, who also serves as his secretary. Upon arriving in Hong Kong, Bill collects firecracker samples for his company, while Charles and Susan canvas the jewelry shops in search of the craftsman who made the phony jewel. After talking to many shop owners, Charles approaches an antique dealer, Wong, who confirms that the imitation was made in Hong Kong. He then has Charles wait as he secretly confers with Stella and Louis in the adjoining room, which is being used for the group's rendezvous. Seeing an opportunity, Stella proposes that she and Louis cut the other two partners out and pay Wong a fair amount for his silence. To keep Otto from meeting with Charles, she and Louis force Charles out through the back door at gunpoint and drive him to a guarded and isolated hideout. Meanwhile, on the shop's stoop, Bill is showing Susan his samples of firecrackers, and when Charles fails to return, they enter and question Wong, who says that Charles made a phone call, then left abruptly through the back. That evening, Stella drugs Otto's tea, and while he is asleep, steals the jewels from his pocket and replaces them with the imitations. The next day, Otto answers Charles' newspaper ad requesting information about the jewels, and Susan covers for Charles by scheduling a meeting in her hotel lobby. By the time of the meeting, Charles has still not returned, so the concerned Susan fills in for him. Meanwhile, Bill recognizes Stella, who is waiting for Otto in the hotel bar. By then, Otto, who has finished his meeting with Susan, enters the bar and overhearing Bill's accusations against Stella, denies them by claiming that Stella is his wife. When Bill tries to call the police, Louis and Tony approach him with guns but their efforts to abduct him are thwarted when the talkative Mrs. Gussy, whom Bill met at the airport, arrives with her new Pekinese dog. After the thugs leave, Bill and Susan exchange stories about their recent experiences and, realizing that Otto is a player in both, report to a police inspector, who is undisturbed by Charles's disappearance, but agrees to check out the antique store. When the inspector reports the next morning that they learned nothing more from the antique shop dealer, Bill suspects that Wong has deceived them all. He and Susan return to the shop as Stella and Louis are preparing to escape with the jewels. When Bill threatens to call the police, Wong pulls out a gun, and Bill and Wong fight. Otto then shows up and refuses to upset negotiations by harming Bill and Susan, so Stella points a gun at Otto and Tony. Bill sets off a firecracker that he had in his pocket, and during the disruption, a gun falls to the floor, which Susan grabs. As Bill fights the thieves, who are also fighting among themselves, Wong shoots Otto and is shot in turn by Susan when he aims the gun at Bill. Just as Bill and Susan gain tenuous control of the situation, the back door bursts open and Charles, who has escaped from his captivity, leads the police into the room where the thieves are then arrested.