In perhaps their most unusual Western adventure, the Three Mesqueteers -- Stony (Bob Livingston), Tucson (Ray Corrigan), and Lullaby (Max Terhune) -- go in search of Professor Marsh (John Van Pelt), an archeologist who vanished while searching for the lost city of Lukachukai. Along for the ride are Marsh's daughter, Betty (Mary Russell); Rutledge (Roger Williams); and an Indian guide, Otah (Yakima Canutt). The expedition heads straight for the Whistling Skull, a huge rock formation in the "nostril" of which the Mesqueteers discover the missing scientist, gaunt but alive among several mummies. Both Rutledge and Otah prove to be less than helpful, however, and at one point Betty and Stony go missing and are feared lost. As Tucson learns, the natives are under the influence of a fanatical white man, but who is he? Oliver Drake and John Rathmell's screenplay was later reworked into a latter-day Charlie Chan thriller The Feathered Serpent (1949), which featured Bob Livingston as the villain.