Fu-Manchu’s slave girl Karamaneh leads sleuths Nayland Smith and Dr Petrie to her evil master’s lair, where they fall prey to another of the Devil Doctor’s traps. Bound hand and foot, they watch helplessly as a party of policemen are imprisoned in a subterranean vault and poisoned with vile fungal spore vapour, while Fu-Manchu cackles with maniacal glee. Can our heroes escape to save the day?