
Wikipedia
Egyptologist Sir Lionel Barton goes to China to find the tomb of Genghis Khan
before Fu Manchu to prevent the latter from using the sword and mask to raise
the people of Asia into a war to wipe out the “white race”. Sir Lionel is
kidnapped before the expedition can leave and tortured by Fu Manchu to reveal
the location of the tomb. His daughter Sheila, who knows its location, insists
on joining the expedition along with her fiancé Terry and a few others,
including British secret agent Nayland Smith. After having found the tomb, Fu
Manchu offers to trade Barton for the sword, which Sheila accepts. Terry
delivers the artifact, but the sword is a fake, secretly made and switched by
Nayland. Barton's dead body is delivered to Sheila and Terry is whipped.
Nayland tries to rescue Terry, but is taken prisoner. Terry is then injected
with a serum that makes him temporarily obedient to Fu Manchu, and is sent to
get Sheila to deliver the real sword and mask to Fu Manchu. She is taken
prisoner and condemned to become a human sacrifice. Nayland is lowered into a
crocodile pit but manages to escape and save Terry from receiving a second
injection of serum that would make him Fu Manchu's slave forever. Using Fu
Manchu's electric arc death ray, they incapacitate the villain just before he
could kill Sheila with the sword. Terry then kills Fu Manchu with the sword,
while Nayland kills his followers with the death ray. On the ship back to
England, they throw the sword into the sea.