In Tangier, Morocco, thugs Ivan and Boris murder informant Pribolov at the orders of their boss, Communist black marketeer H. Kozad. Boris then goes to the notorious Crossroads Café nightclub, where he keeps an eye on American Steve Gordon. Moments later, tour guide Blalu brings American tourist Millicent McLean into the bar. Millie is intrigued when Blalu points out Steve as an infamous black marketeer. After Steve comes to Millie’s aid by capturing a thief who has stolen her purse, police inspector Paul Rabat informs Steve about Pribolov’s death. However, after the inspector leaves, Steve is unsure if Rabat was threatening him or warning him. Millie also departs, furious that Steve has rebuffed her flirtations. Steve then confides in his best friend, nightclub owner Tony Agazian, that Pribolov was working for him and told him about Kozad’s private wall-safe. Later that night at his hotel, Steve reluctantly gives in to Millie’s charms and agrees to meet her for breakfast. The next morning, Steve listens to a radio broadcast about the disappearance of several atomic scientists, then discovers a listening device in his hotel room. After disabling the device, Steve telephones Kozad and, after warning him that he is aware that Kozad planted the device in his room, demands that Kozad now bring him a payment for a recent shipment. Steve, who is actually an American undercover intelligence agent, is later contacted via secret telephone by Henry Morrison, head of the American Legation, who assigns him to pick up Nadine Zant at the airport. As a result, Steve cancels his breakfast plans with Millie. Steve is knocked unconscious outside the airport by Kozad’s thugs, who then kidnap Nadine. Millie, who has been following Steve, revives him and tells him what she saw. Based on her information, Tony and Steve find Nadine and rescue her, unaware that the woman they have rescued is actually Olga Petrov, one of Kozad’s Communist spies who is posing as Nadine. Kozad, meanwhile, has captured Nadine and explains to her that he knows she was sent to Tangier by the British to identify her English diplomat uncle who was recently disfigured in an accident. The British and American governments are seeking her uncle, who is sympathetic to the Communists, because he and Kozad are arranging a meeting of the missing atomic scientists, each of whom holds key information to create a hydrogen bomb. In order to protect the woman he believes is Nadine, Steve cancels dinner plans with Millie and instead dines with Olga. Meanwhile, Nadine escapes her captors and contacts Tony at the café. As Steve meets with Tony and Nadine in the café’s kitchen, Italian chef Vittorio warns Olga that Steve is two-timing her with Nadine. Olga flees, and Steve returns to find a very persistent Millie in her place. Nadine is secured in a hotel room under Tony’s protection, after which Steve urges Millie to stop following him for her own safety. However, she ignores his advice and follows him to Kozad’s home. Just after Steve successfully steals a coded message from Kozad’s safe, Millie shouts a warning that Boris is about to attack him. After knocking Boris unconscious, Steve returns with Millie to their hotel. Kozad, meanwhile, worries that Steve will decipher the coded message and orders him killed. While they are alone together in her room, Millie renews her earlier plea that Steve abandon his life of crime and join her in Cleveland, Ohio, where she will secure him a job at her father’s company. Steve then reveals his true vocation as an American agent and explains that he is now bringing a coded radiogram to the American Legation. Unknown to Steve, Millie drops a note out the window to Ivan, who then knocks Steve unconscious and steals the radiogram. Having memorized the contents, Steve nevertheless delivers the message, which states that Nadine’s uncle will arrive at the airport the next day. That day, however, Millie appears at Steve’s room as an apparent hostage of Kozad’s thugs, who then kidnap Steve and Nadine and take them to Kozad’s office. Although Kozad intends to kill the American agent, Steve kills him first with a knife which he had concealed in his hatband. Millie then reveals her true identity as the head of the Communist spy ring in Tangier, and holds Steve at gunpoint. Steve, who had been on his guard the entire time, is not surprised as he grew up in Cleveland and knew her father’s supposed company did not exist, and also assumed the purse-snatching was a set-up. Before Millie can fire her weapon, Nadine shoots her and holds Kozad’s thugs hostage. Later, a radio broadcast reports that the missing atomic scientists were apprehended at the Tangier airport. Tony, Henry, Steve and Nadine celebrate at the restaurant, where Rabat arrests Vittorio as one of the traitorous scientists. Rabat also reveals that he arrested Olga before she escaped, thereby proving that he has been on Steve’s side all along.