The plot pits a poor sidewalk artist against a fiendish mastermind who is not only intent on world domination, but determined to kill all white people and for reasons that are never made entirely clear, wants to create nymphs, satyrs, and other Greek and Roman demigods through the miracle of vivisection These characteristics alone would qualify Caspar Pettifranc to take his rightful place alongside John Sunlight, Wu Fang, Doctor Death and the other great villains of the American pulps, but Goddard doesn't stop here. The author also makes Pettifranc a master of voodoo who thus can ring in zombies and the pantheon of loas. For reasons that the author allows to remain obscure, the loas are given to making odd whistling noises, hence the title of the book.