Upon the murder of a police agent in Tangiers, North Africa, the international police assemble to plan how to break the notorious contraband ring that they hold responsible for the agent’s murder and many others.  The group approves the suggestion of the United States representative Mr. Farrell to assign the case to a female former OSS agent whose identity will be known only to Farrell.  The agent, Joanna “Jo” Dane, arrives in Tangiers, where she is spotted by smuggler Van Logan, who follows her to the Ritz Hotel.

After checking in, Jo meets with Farrell, who advises her to frequent Ali Baba’s bazaar and Frisco’s Bar, where her only contact will be the Moorish doorman.  Moments after Jo leaves Farrell, he is murdered and Jo becomes suspicious of Van, who breaks into her room shortly thereafter.  When Jo tells Van she is looking for work, he recommends she try Frisco’s Bar.

Later that evening after secretly telling the Moor about Farrell’s murder, Jo is surprised to learn that Frisco is a woman, but impresses the bar owner with her card dealing ability and gets a job.  Van arrives at the bar later and admits to Jo that he uses his boat to transport items abroad, but does not consider himself a smuggler.  French smuggler Paul Dupont asks Van to introduce him to Jo, but Frisco privately cautions Jo to stay away from Dupont.  Afterward, a confederate of Dupont’s, Augie, gets involved in a brief brawl with Van and his assistant Danny until Dupont orders him away.

The following day Van, distrustful of Jo, takes her to a scent shop in Ali Baba’s bazaar, but the shop’s owner and Van’s cohort, Mustapha, later reveals he has no information on Jo’s identity.  Convinced that Dupont could be the lead she needs, Jo flirts with him the next night at Frisco’s, and, despite another warning from Frisco, persuades him that she might be helpful in selling smuggled goods on his trip to Spain.

The next morning, Van and Danny are surprised and upset when Dupont and Jo arrive at the dock and Dupont insists that Van transport the couple to Malaga on board Van’s boat, the Banshee.  Mustapha, working for the syndicate head, learns that the Banshee ’s shipment from French Morocco has been hijacked by Dupont and orders Augie to pursue him.  The Banshee breaks down at sea, allowing Augie and the crew of the Narcissus to catch them.  After Augie’s men transfer the Banshee ’s cargo aboard their boat, Van makes a reckless get-away on the repaired Banshee, taking Jo and Dupont to Port of Spain.  Before arriving, Van warns Jo to drop Dupont, but although attracted to Van and worried about Dupont, she refuses.

Later with Dupont, Jo feigns displeasure that he no longer has any cargo to sell.  Dupont then reveals that he has a key to a box that contains crucial information on the smuggling syndicate and is negotiating with several counties for the sale of the key.  Having eavesdropped on the couple, Danny reports this news to Van, who then demands a cut of the sale.  After docking, Dupont plants illegal goods on Van, who is stopped at customs, while Dupont and Jo depart unimpeded.  Van is interrogated by the local police, but escapes and meets Danny at a prearranged spot, where his partner informs him of Jo and Dupont’s location.

Dupont decides to drive to Malaga alone to escape possible detection, and when Jo complains that he does not trust her, he gives her the key, but not the location of the box.  Before Dupont can leave, however, he is murdered by Augie, who then chases Jo, before she manages to escape.  While attempting to flee in Dupont’s rented car, Jo is surprised by Van, who demands the key, which Jo pretends not to have.  When Van finds the key in her purse and refuses to return it, Jo shoots him and escapes.  Wearing a bulletproof vest, Van is soon revived by two British tourists, Pebbles and Potts, who help him return to town.

After hastily returning to Tangiers, Jo learns by accident that Dupont’s key fits an American Express box, but on her way to their offices, is pursued again by Augie.  Jo then heads to Frisco’s for sanctuary and passes the key on to the Moor.  Once inside the bar, however, Jo realizes that Augie works for Frisco, who is revealed as the head of the contraband syndicate.

Meanwhile Van, who is really a police agent, returns from Spain and reports to the police group, who have just received the key from the Moor.  Van is shocked to learn that Jo is the other agent on the case and hastens to Frisco’s knowing she is in danger.  Augie, believing that Jo still has the key, refuses to kill her on Frisco’s order and instead shoots the bar owner and kidnaps Jo.  Before dying, Frisco manages to tell Van about Augie’s hideout.  Augie takes Jo to a mountain cave, where they are confronted by the police, including Danny and Van.  Danny is killed and Van kills Augie and rescues Jo.  Outside the cave, Van is surprised to find Pebbles and Potts, who reveal their identities as British police agents also following Van and Jo, who are now free to express their feelings for each other.