Nyland Smith and Paul Sterling have fallen into the hands of Dr. Fu Manchu and are kept prisoners in his underground laboratories. Fu Manchu has decide that Smith and Sterling are to join the legion of the living dead and the injection transforming them in to zombies is made. However, Fa Lo Swee, Fu Manchu's daughter, in an effort to save them to gain her own ends, renders the injection harmless but she cautions the prisoners that they must pretend, for that is their only chance. she offers to help Sterling gain his freedom if he will consent to take the girl Florette with him. Fa Lo Swee disagrees with her father's plan to make Florette a bride of Fu Manchu. Meanwhile Superintendent Weymouth in his search for Smith contacts the French authorities...