After a pilot testing a device by which his plane is guided by remote control is hijacked, Charlie Chan of the Honolulu police comes on the case. Chan finds the plane with the device, which could be sold for millions to a foreign power, gone and the pilot dead. Later, he also locates the body of the murderer, Miller. Chan, Hopkins, the airplane owner, and Cartwright, the inventor of the device, take the dirigible Hindenburg to Berlin to investigate three people traveling there by ocean liner: Dick Masters, an Olympic pole-vaulter and aviator, who did not pilot the plane the day of its disappearance because of an injured shoulder; Yvonne Roland, who visited Miller's room; and Arthur Hughes, an arms dealer, who wanted to buy the device. In Berlin, Chan finds the device hidden in a box in the luggage of Masters' girl friend Betty Adams. He substitutes a book and returns the box to Hopkins. Cartwright tells Chan that Hughes accused Hopkins of double-crossing him and threatened to expose Hopkins' plan to sell the device to a foreign government, and that Hopkins escaped with the box. Masters is now suspected because the box was found in Betty's room and the fact that he was on the boat with Roland. Roland, however, takes the box to a foreign diplomat, the Honorable Charles Zaraka, who discovers the book instead of the device. After Hughes learns of this, Chan's son Lee, an Olympic swimmer, is kidnapped. Following instructions sent from the kidnapper, Chan brings the device, which he has had removed and replaced with a transmitter, to an agreed upon location. He is then taken to Zaraka's estate, where Hopkins identifies the device. Hughes arrives with his thugs and fights Zaraka's henchmen for the device before he discovers that it is a phony. After the police arrive and Hopkins is shot, Chan reveals that Cartwright shot him, and that earlier Cartwright murdered Miller and made it appear that Hopkins stole the device. Hopkins recovers and Lee wins the hundred meter race.