The beheading of international criminal mastermind Fu Manchu is witnessed in China by his nemesis Nayland Smith. Back in England, however, it is increasingly apparent that Fu Manchu is still operating. Smith is quick to detect that the execution he witnessed was that of a double, an actor hypnotised into taking Fu Manchu's place. The villain is back in London, working from a secret base underneath the River Thames. He has kidnapped the esteemed Professor Muller, who holds the key to a potentially deadly solution from the seeds of a rare Tibetan flower.
In 1924, Fu Manchu, his army of henchmen and his vicious daughter Lin Tang are kidnapping the daughters of prominent scientists and taking them to his remote island, where he demands that the fathers help him to build a device that transmits blast waves through a radio transmitter, which he intends to use to take over the world. He plans to keep (even wed) the girls in question. But Fu's archenemy, Nayland Smith of Scotland Yard, is determined not to let that happen.
In his remote hideaway in the China province of Gansu, the evil Fu Manchu (Christopher Lee) plots the death and downfall of his arch rival, Inspector Nayland Smith of Scotland Yard, as the first step in his plan to become leader of the world's most terrible criminals.
In his remote jungle hideout, the evil Fu Manchu has discovered a deadly poison in a "lost city" in the Amazonian jungle that affects only men. Women can become carriers of the "kiss of death" by being bitten by venomous snakes. The poison causes blindness and is ultimately followed six weeks later by death. Using mind control, he aims the women at Nayland Smith and other key people with political influence. This prevents them from interfering with his own ambitions to prepare millions of "doses" and spread them around the world's major cities and capitals in a plan to gain world domination.
Supercriminal Fu Manchu plots to freeze the world's oceans with a diabolical new device. With his evil daughter, Lin Tang, his army of Dacoitys, and the help of the local crime organization led by Omar Pasha (whom Fu Manchu double-crosses), Fu Manchu takes over the governor's castle in Istanbul which has a massive opium reserve, to control the largest opium port in Anatolia, a fuel for his machine. Fu Manchu needs the help of an intelligent scientist with an ailing heart whom he has imprisoned. In order to keep the scientist alive he kidnaps a doctor and his wife to give the scientist a heart transplant from one of his obedient servants. Opposing him from Britain's Interpol are his nemeses Nayland Smith and Dr. Petrie.