There came to them out of the fog--seemingly from a great distance--the sound of a laugh, a low, deliberate, soulless laugh which had no more of joy than that of a hyena night-prowling in the desert; a laugh that rose by slow gradation, louder and louder, clearer, more distinct and terrible, until it seemed barely outside the narrow circle of their vision; a laugh so unnatural, so unhuman, so devilish, that it filled those hardy man-hunters with a sense of dread unspeakable!