I backed against the wall, crouching low, revolver in hand, scarcely venturing to breathe, listening intently for the slightest sound to break the intense silence.  My heart beat like a trip-hammer, and there were beads of cold perspiration on my face.  The change had occurred so swiftly as to leave me quaking like a coward at the unknown terrors of the dark.  Yet almost within the instant I gripped my nerves, comprehending all that had occurred, and confident of my own safety.  There must be another opening into this underground den—­one leading to the outer air—­judging from that sudden and powerful suction.  The very atmosphere I breathed had a freshness to it, inconceivable in such a place otherwise.  With the first return of intelligence my mind gripped certain facts, and began to reason out the situation.  That sudden sweep of air could only have originated in the opening of some other barrier—­a door no doubt leading directly to the outside.  I had seen no occupant of the room; without question it was deserted at my entrance.  Yet someone had been there, and not long before, as was evidenced by the burning candle.  Nor, by that same token, did this same mysterious party expect to be absent for any length of time.  Apparently I had intruded at the very moment of his departure.  Wherever that second passage might be, the former occupant of this underground den had evidently entered it previous to my opening the inner door.  Still unaware of my presence he had unfastened some other barrier, and the resultant draught had extinguished the candle, and blown shut the door at my back.  This seemed so clearly the truth that I laughed grimly behind clinched teeth.  The solution was easy; I had but to discover the extinguished candle, relight it, search out the second passage, and waylay the fellow when he returned unsuspicious of danger.

Confident as to the correctness of my theory, and eager for action to relieve the tension on my nerves in that black silence, I began feeling a way along the wall toward the right, in the direction where I remembered the iron light bracket to be situated.  The rough stone surface was unbroken, and I encountered no obstacles under foot, my groping search being finally rewarded by touch of the iron brace.  I could clearly trace the form of the bracket, and determine how it was fastened into place, yet to my astonishment there was no remnant of candle remaining in the empty socket.  Grease, still warm to the touch, proved conclusively that I had attained the right spot in my search, yet the candle itself had disappeared.  Beyond doubt the draught of air had been sufficiently strong to dislodge it from the shallow socket, and it had fallen to the floor.  I felt about on hands and knees, but without result, and finally, in sheer desperation, struck my last match.  The tiny flare was sufficient to reveal the entire floor space as well as the wall, but there was no remnant of candle visible.  I held the sliver of wood, until the flame scorched my fingers, staring about in bewilderment.  Then the intense darkness shut me in.