There is an intermediate ground between our knowledge of life and the unknown which is readily conceived as covered by the term mysticism. Mystery stories of high rank often fall under this general classification. They are neither of earth, heaven nor Hades, but may partake of either. In the hands of a master they present at times a rare, if even upon occasion, unduly thrilling—aesthetic charm. The examples which it has been possible to gather within the space of this volume are offered as the best of their type.