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.