The stories in this collection, inasmuch as they constitute a somewhat new departure in this class of literature, require a few words of introduction. The primary function of all fiction is to furnish entertainment to the reader, and this fact has not been lost sight of. But the interest of so-called "detective" fiction is, I believe, greatly enhanced by a careful adherence to the probable, and a strict avoidance of physical impossibilities; and, in accordance with this belief, I have been scrupulous in confining myself to authentic facts and practicable methods.