En route to a police convention in New York, Charlie Chan meets his old friend, Hugh Drake, a British intelligence officer who is on the trail of Paul Narvo, the spy who has been sabotaging U.S. built bombers bound for England. At the airport in New York, Drake is met by his host, aircraft tycoon George Kirby, who invites Chan to a party he is giving for Drake. Later that night, Chan arrives at Kirby's party to find Drake murdered by a poison gas pellet. Aided by police inspector Vance, Chan interrogates the assembled guests: Herbert Fenton, Drake's old school friend; actress June Preston; stockbroker Richard Jeffrey; Ralph Percy, an aircraft designer; and Kirby's butler, Boggs. Learning little from the guests, Chan tracks down Narvo's ex-wife, Patricia Shaw, who explains that she fled from her husband and his sinister servant, Rumullah, upon learning that he was a spy. Chan also questions David Elliott, a chemist who visited Drake on the night of his death. After Chan's search for Rumullah ends in the servant's death and Kirby is found poisoned, Chan assembles all the suspects on the test flight of a bomber that is to be sabotaged by poison gas pellets. As the bomber descends to the level that will trigger the gas, Fenton grabs the hidden pellets, revealing himself to be involved in the plot. As the plane lands safely, however, Chan announces that Fenton is too old to be Narvo, and then cleaverly tricks the real Narvo, Dick Elliott, into exposing himself as the spy.