Tony Dumont [Rory Calhoun] is aboard a plane bound for the Crown Colony of Hong Kong, carrying a shipment of industrial diamonds. The flight is hijacked by armed men who flee with the gems, leaving Tony and the other passengers behind, including famed novelist Pamela Vincent [Barbara Rush]. They are rescued and taken to Hong Kong, but Tony does not get a proper goodbye because Pamela is mobbed by the press.
Tony returns to Macau, where he operates as the head of the local operations for an international crime syndicate and had helped plot the heist. His childhood friend and Bangkok operations head Quisto [Paul Picerni] calls with news of a freighter hijack tied to their syndicate that will need unloading offshore.
Tony takes his girlfriend Jean Blake [Dolores Donlon] to a nightclub run by Mama Lin [Soo Yong], the woman who raised him as an orphan. There that night he runs into Lobero [Aram Katcher], a former ally who refuses to sell his own San Francisco smuggling operation to the syndicate. Pamela Vincent is among the club’s patrons, renewing their acquaintance. Bendesh [Werner Klemperer], the syndicate boss, warns Tony that a rival gang is planning to seize the hijacked cargo. Tony and his trusted lieutenants, Nicco [Pat Conway] and Boris [Mel Welles], head to the freighter by speedboat to oversee the transfer of the stolen diamonds onto junks. When rival gangs arrive to intercept, Tony’s crew uses speed, maneuverability, and hand grenades to prevail.
Jean Blake is furious at being left at the club, and Bendesh later accuses Quisto of orchestrating the attempt to steal the cargo, ordering Tony to kill him. Quisto appears at Tony’s door and pleads for help. Tony tries to aid him in escaping to Hong Kong, but when confronted by Nicco, he is forced to choose and sends his old friend to his death, dropped into a net behind a junk and dragged through the harbor. The loss unsettles Boris, who decides to leave the business and seek honest work on a ship.
Romance shifts as Tony grows closer to Pamela Vincent, and Jean leaves him. Lobero then contacts Tony with a plan to steal a million dollars’ worth of diamonds from a syndicate courier before delivering them to Lobero. To escape, Tony fakes his own death, and leaves his affairs to Jean and Mama Lin. He sneaks onto a freighter and begins a year-long voyage to San Francisco, hoping to throw the syndicate off his trail. When he reaches the West Coast, Lobero isn’t in town, so he looks up Pamela only to find she has written a new novel in which a character based on him appears, and she is romantically involved with a professional tennis player. He then learns Lobero has been murdered by a syndicate gunman. The pursuit resumes as syndicate men spot him and chase him to the piers, where Boris tracks him down and helps him board a ship bound for Hong Kong.
After a dangerous escape, Tony reconnects with Mama Lin and Jean, who are glad he is alive. They plan to meet, but the syndicate follows, forcing the trio to split up. Mama Lin seeks help from a police officer, who arrests one of the pursuing men and signals the possible presence of Nicco, the Macau chief. Mama Lin and Tony rendezvous at the Botanical Gardens and proceed to Victoria Gap to pick up Jean, only to be followed by Nicco and his henchmen. The trio makes for the Star Ferry, but Nicco remains close behind. As the women board the ferry, Tony tries to return the diamonds, but Nicco says it is too late. In the ensuing chaos, the syndicate is able to intervene, and the police arrive to arrest the pursuing crew, leaving the women to wonder what lies ahead for Tony.
