But my candle was inadequate for more than the most superficial examination of the ceiling, which presented so far as I could see an unbroken surface.  I turned my attention, therefore, to the floor.  It was when I was turning the rug back that I recognized the natural and not supernatural origin of the sound which had so startled me.  It had been the soft movement of the carpet across the floor boards.

Some one, then, had been there before me—­some one who knew what I knew, had reasoned as I reasoned.  Some one who, in all probability, still lurked on the upper floor.

Obeying an impulse, I stood erect and called out sharply, “Sperry!” I said.  “Sperry!”

There was no answer.  I tried again, calling Herbert.  But only my own voice came back to me, and the whistling of the wind through the window I had opened.

My fears, never long in abeyance that night, roused again.  I had instantly a conviction that some human figure, sinister and dangerous, was lurking in the shadows of that empty floor, and I remember backing away from the door and standing in the center of the room, prepared for some stealthy, murderous assault.  When none came I looked about for a weapon, and finally took the only thing in sight, a coal-tongs from the fireplace.  Armed with that, I made a cursory round of the near-by rooms but there was no one hiding in them.

I went back to the rug and examined the floor beneath it.  I was right.  Some one had been there before me.  Bits of splintered wood lay about.  The second bullet had been fired, had buried itself in the flooring, and had, some five minutes before, been dug out.

VII

The extraordinary thing about the Arthur Wells story was not his killing.  For killing it was.  It was the way it was solved.

Here was a young woman, Miss Jeremy, who had not known young Wells, had not known his wife, had, until that first meeting at Mrs. Dane’s, never met any member of the Neighborhood Club.  Yet, but for her, Arthur Wells would have gone to his grave bearing the stigma of moral cowardice, of suicide.

The solution, when it came, was amazing, but remarkably simple.  Like most mysteries.  I have in my own house, for instance, an example of a great mystery, founded on mere absentmindedness.

This is what my wife terms the mystery of the fire-tongs.

I had left the Wells house as soon as I had made the discovery in the night nursery.  I carried the candle and the fire-tongs downstairs.  I was, apparently, calm but watchful.  I would have said that I had never been more calm in my life.  I knew quite well that I had the fire-tongs in my hand.  Just when I ceased to be cognizant of them was probably when, on entering the library, I found that my overcoat had disappeared, and that my stiff hat, badly broken, lay on the floor.  However, as I say, I was still extraordinarily composed.  I picked up my hat, and moving to the rear door, went out and closed it.  When I reached the street, however, I had only gone a few yards when I discovered that I was still carrying the lighted candle, and that a man, passing by, had stopped and was staring after me.