Globetrotting newspaper correspondent James Montgomery Wilson returns to Bombay to learn that his fiancée, Frankie Gilroy, is going back to San Francisco, as she is upset that Jim has twice left her "standing at the altar." Jim then goes to Christopher Ruggles, his boss at Amalgamated News Service, and tells him that he is quitting, because he has promised Frankie that he will return to the United States with her. Ruggles offers him a desk job in their San Francisco office if he agrees to do one more story, one concerning a mysterious shipment of Indian diamonds leaving the country on the seaplane, the "Bombay Clipper." Back at his hotel, Jim's attempts to question some of the "Clipper's" passengers are halted when he is knocked unconscious by a mysterious man named Chundra. Jim, however, manages to make it to the plane just before take-off, and he and Frankie are married by the plane's captain. During the flight to Manila, the two soon begin fighting when Frankie learns that Jim has yet to quit his job, and Jim's troubles are compounded when Chundra intercepts a telegram he sent to Ruggles. That night, the plane's steward catches passenger Jeremiah Lamb trying to steal the diamonds, but accidentally kills the crook before learning that the jewels have been stashed in Frankie's dressing case. The captain then informs the plane's passengers that they will not be allowed to leave the plane until they can be questioned by the Singapore police. Later, Frankie finds the diamonds, and Jim decides to keep them in hopes of catching the murderer. The plane arrives in Singapore, where Jim is questioned by the police. After he suggests that Lamb may have been the diamonds' courier, passenger George Lewis steps forward and tells him that he is the real courier. Jim then agrees to give the diamonds back, in exchange for the exclusive story. Lewis tells him that the diamonds are a royal gift from India to Great Britain, and they are being sent to the United States to be cut for use in making war armaments. Before they can pick up the diamonds, however, the steward steps forward and confesses to Lamb's murder. The chief inspector then orders all the passengers ashore, and they are placed in the Hotel Continental for an inquest. Later that evening, after a day of sight-seeing, Lewis is poisoned while having dinner with Frankie. He manages, however, to give the diamonds to Jim before he dies. Back aboard the "Clipper," Jim is attacked by fellow traveler Bland, who takes the diamonds from him, then throws him out of the plane. He is rescued, however, by Chundra, who Jim learns is a secret agent for the Indian government. Bland is put under arrest, and the captain informs the passengers that no one will be allowed off the plane in Manila until the diamonds are recovered. The leader of the foreign agents, Dr. Gregory Landers, then hijacks the plane and arranges a sea rendezvous with a submarine. Jim, with the help of passenger Tom Hare, overtakes the hijackers, but Tom, a discredited aviator, is wounded in the ensuing gunfight. He still manages to fly the seaplane to safety and is proclaimed a hero in Jim's front-page story.