In Port of Spain, Trinidad, Inspector Smythe investigates the apparent suicide of American artist Neal Emery. At the Cari-b club, where Neal's wife Chris works as a singer and dancer, Smythe informs her about her husband's death and asks about the Emerys' connections with wealthy Max Fabian, who had recently paid Neal a large sum of money. When Smythe suggests that a romantic tie exists between Fabian and Chris, she grows angry. The next day, Smythe summons Chris to headquarters, where he lifts her passport and informs her that the medical examination on Neal indicates that he was murdered. A local fisherman witnessed Neal's small boat at Fabian's landing and Smythe has enough evidence to arrest him. Smythe then reveals that the police are aware that Fabian is the center of a political group that buys and sells sensitive information, but lack hard evidence to convict him. Smythe suggests to Chris that she spy on Fabian for the police and provide the crucial proof needed to halt his secret organization as a way to avoid an ugly trial. Later that afternoon, Neal's older brother Steve, a pilot, arrives from America and upon learning of his brother's murder, hastens to the courthouse where the inquest is in progress. When Chris testifies, she admits Neal spoke often of suicide, a lie that indicates her willingness to help Smythe. Steve follows Chris home, then angrily confronts her with the sordid newspaper accounts of a possible love triangle between Neal, Chris and Fabian. Smythe telephones Chris and warns her not to confide in Steve until his connections can be checked out. That evening, Steve apologizes to Chris and shows her a letter he had received from Neal asking him to come to Trinidad for a job. Chris is startled by the distinctive crest on Neal's letter and invites Steve to stay in Neal's room. Steve asks her if she will return to America with him, but she avoids answering. The next day Steve goes to the Cari-b and pays Mr. Wittol, the owner and a cohort of Fabian, the money that Neal owed. Steve then informs Chris that he has decided to stay longer and asks her to show him the island. A few days later, Chris and Steve arrive at the house to find Fabian waiting to remind Chris of a dinner date, to which he also invites Steve. That evening at Fabian's, Steve notices the cocktail glasses carry the same crest found on Neal's letter. Fabian is startled by the unexpected early return of his house guests, Dr. Franz Huebling, his wife Veronica, Peter Bronec and Mr. Walters. After Steve recalls having read an article by Huebling on Germany's V-2 rockets, Fabian steers Chris to the patio, where he asks her to go away with him, but she demurs. Upon returning to Chris's house, Steve accuses Chris of being bought by Fabian. Later, however, Chris tells Steve about her relationship with Neal and that there is nothing between her and Fabian. Steve admits he has fallen in love with her and asks her to return to the States with him, but when she refuses without explanation, he storms away. The next day, Steve takes Neal's letter to Smythe, insisting that it implicates Fabian, and becomes angered by Smythe's apparent disinterest. When Chris tells Smythe about Fabian's guests, he insists that she find out more information. Smythe learns Bronec is flying out that afternoon and arrives at the airport in time to see Bronec run over by a car. In his effects, Smythe discovers a key, which he passes on to Chris as means to get into Fabian's guesthouse. Steve, meanwhile, stays away from Chris's and after questioning a number of the local fishermen, is attacked by Walters. Chris attends a party at Fabian's, which Steve crashes and makes accusations against Fabian. Chris hastily covers for Steve, then performs one of her club dance numbers, which infuriates Steve, who departs. Chris promises Fabian she will remain the night, then sneaks into the guesthouse and finds blueprints and figures. When the others return, Chris is forced to hide, accidentally leaving behind a handkerchief gift from Fabian on the desk. Before sneaking away, she overhears the group discussing plans to create a secret rocket launch site on the island, which will bring a large enemy country within striking distance of the entire United States. Meanwhile, Smythe grills Wittol about his involvement in Bronec's murder and Wittol confesses. Recalling the handkerchief, Chris slips back into the guesthouse, but it has vanished. At the main house, Veronica presents Fabian with the handkerchief, which Huebling had discovered. Realizing Chris's involvement, Fabian and the group begin packing, intending to flee and force Chris along. Now aware of Chris's danger, Steve returns, and in the ensuing shootout, wounds Fabian. When Smythe and his men arrive, Fabian makes a final effort to escape but Steve kills him. With the ring smashed, Chris is allowed to depart for Chicago with Steve.