I got to the top, however, without incident.  I could see fairly well after the darkness of the house beneath, but there was nothing suspicious in sight.  The roofs, separated by two feet of brick wall, stretched around me, unbroken save by an occasional chimney.  I went very softly over to the other trap, the one belonging to the suspected house.  It was closed, but I imagined I could hear Johnson’s footsteps ascending heavily.  Then even that was gone.  A near-by clock struck three as I stood waiting.  I examined my revolver then, for the first time, and found it was empty!

I had been rather skeptical until now.  I had had the usual tolerant attitude of the man who is summoned from his bed to search for burglars, combined with the artificial courage of firearms.  With the discovery of my empty gun, I felt like a man on the top of a volcano in lively eruption.  Suddenly I found myself staring incredulously at the trap-door at my feet.  I had examined it early in the evening and found it bolted.  Did I imagine it, or had it raised about an inch?  Wasn’t it moving slowly as I looked?  No, I am not a hero:  I was startled almost into a panic.  I had one arm, and whoever was raising that trap-door had two.  My knees had a queer inclination to bend the wrong way.

Johnson’s footsteps were distinct enough, but he was evidently far below.  The trap, raised perhaps two inches now, remained stationary.  There was no sound from beneath it:  once I thought I heard two or three gasping respirations:  I am not sure they were not my own.  I wanted desperately to stand on one leg at a time and hold the other up out of focus of a possible revolver.

I did not see the hand appear.  There was nothing there, and then it was there, clutching the frame of the trap.  I did the only thing I could think of; I put my foot on it!

There was not a sound from beneath.  The next moment I was kneeling and had clutched the wrist just above the hand.  After a second’s struggle, the arm was still.  With something real to face, I was myself again.

“Don’t move, or I’ll stand on the trap and break your arm,” I panted.  What else could I threaten?  I couldn’t shoot, I couldn’t even fight.  “Johnson!” I called.

And then I realized the thing that stayed with me for a month, the thing I can not think of even now without a shudder.  The hand lay ice cold, strangely quiescent.  Under my fingers, an artery was beating feebly.  The wrist was as slender as—­I held the hand to the light.  Then I let it drop.

“Good Lord,” I muttered, and remained on my knees, staring at the spot where the hand had been.  It was gone now:  there was a faint rustle in the darkness below, and then silence.

I held up my own hand in the starlight and stared at a long scratch in the palm.  “A woman!” I said to myself stupidly.  “By all that’s ridiculous, a woman!”

Johnson was striking matches below and swearing softly to himself.  “How the devil do you get to the roof?” he called.  “I think I’ve broken my nose.”