Dr. Fu Manchu has poisoned the renowned Dr. Hu Yan, who is to appear at a conference of the nations of the world, and replaced him with an impostor who will disrupt the conference's goal--a plan for world peace.
In his search for a treasure of gold, Dr. Fu Manchu commits a brutal murder. Afterwards, he sends one of his assassins to finish off the only witness to the crime, who happens to be the victim's wife.
Dr. John Petrie is sent to Mozambique to determine if Big Syd Vesta, an American gangster who is on the lam, is sufficiently healthy to return to the United States to stand trial. With Dr. Fu Manchu's help Vesta fakes his death. In return Vesta uses his connections with U.S. organized crime elements to stage a string of bank robberies all as dress rehearsals for their biggest crime - robbing the six biggest banks in New York City simultaneously.
Dr. Fu Manchu threatens to destroy humanity with a plague unless the United States turns over an island key to its Pacific defenses to him so that he in turn can sell it to the highest bidder.
Dr. Fu Manchu has stolen a deadly collection of germ cultures from a laboratory in San Francisco, and plans to smuggle them through the port of Hong Kong.
Dr. Fu Manchu kidnaps a renowned plastic surgeon, whom he plans to force to operate on Adolf Hitler--who is actually still alive and in hiding. Then Fu and Hitler will join forces to conquer the world.