A runaway boy pretends to be the son of a Navy man, only to turn both their lives upside down.

Cisco and Gordito arrive to find there is an outlaw operating in the area who is assumed to be the Cisco Kid. When a reward is offered for his capture and a large shipment of money goes out, Cisco is on hand. Seeing the gang rob the stage he goes after them only to be wounded. The gang leader leaves Cisco's handkerchief at the scene and now he is wanted for the murder he tried to break up.

A pretty Chinese woman, seeking help from San Francisco detective James Lee Wong, is killed by a poisoned dart in his front hall, having time only to scrawl "Captain J" on a sheet of paper. She proves to be Princess Lin Hwa, on a secret military mission for Chinese forces fighting the Japanese invasion. Mr. Wong finds two captains with the intial J in the case, neither being quite what he seems; there's fog on the waterfront and someone still has that poison-dart gun...

The nefarious Dr. Fu Manchu searches for the keys to the tomb of Genghis Khan, in order to fulfill a prophecy that will enable him to conquer the world. His nemesis, Dr. Nayland Smith, Qiwan.cc and his associates fight to keep the evil doctor from getting his hands on the keys.