Sir Gregory Hale returns to London from Mongolia with a mysterious Tulun-Nur chest that holds the "key to India, " a vital secret of the Fu Manchu's notorious Si-Fan organization. Unfortunately Hale is murdered before he is able to disclose the secret to Nayland Smith. The Burmese police commissioner and Dr. Petrie launch a mission to affront the brilliant but deadly master criminal before he succeeds in his malignant and fantastic plot to take over the world.