Soon after a Chinese princess comes to the US to buy planes for her people, she is murdered by a poison dart fired by an air rifle.

Detective Charlie Chan springs into action when top officials of a New Orleans chemical company begin dropping like flies.

Charlie attempts to solve a triple murder in which a dead man's finger prints show up at all three murder sites, and all three victims were connected with the conviction and execution of an evidently innocent man.

A gold mine in Arizona, that was formerly losing a lot of money, suddenly turns into a veritable money-making machine. However, the owner, instead of being happy about his now profitable business, insists to Charlie that something is fishy and that someone is out to murder him. Charlie and his "crew" travel to the mine, pretending to be tourists staying at a nearby dude ranch so as not to arouse suspicion, and discover that the owner may well be right--it looks like the mine is being used as a cover for criminal activities, and that someone is indeed out to murder him.

In order to learn the location of a fabled Aztec treasure, a professor kidnaps his colleague, the only man able to read the ancient Aztec script that is supposed to reveal the location of the treasure. Charlie Chan and his #1 and #2 sons journey to the jungles of Mexico to find the victim and bring the kidnapper and his gang to justice.

All the passengers on an airplane headed for San Francisco are drugged, and when they wake up, it is discovered that a quarter-million dollars is missing. Charlie Chan--and, of course, his #1 son--must discover the identity of the person who doped the passengers and stole the money.