“Toothache?” I asked, not too gently.  “You deserve it.  A woman of your age, who would rather go around with an exposed nerve in her head than have the tooth pulled!  It would be over in a moment.”

“So would hanging,” Liddy protested, from behind the hot-water bottle.

I was hunting around for cotton and laudanum.

“You have a tooth just like it yourself, Miss Rachel,” she whimpered.  “And I’m sure Doctor Boyle’s been trying to take it out for years.”

There was no laudanum, and Liddy made a terrible fuss when I proposed carbolic acid, just because I had put too much on the cotton once and burned her mouth.  I’m sure it never did her any permanent harm; indeed, the doctor said afterward that living on liquid diet had been a splendid rest for her stomach.  But she would have none of the acid, and she kept me awake groaning, so at last I got up and went to Gertrude’s door.  To my surprise, it was locked.

I went around by the hall and into her bedroom that way.  The bed was turned down, and her dressing-gown and night-dress lay ready in the little room next, but Gertrude was not there.  She had not undressed.

I don’t know what terrible thoughts came to me in the minute I stood there.  Through the door I could hear Liddy grumbling, with a squeal now and then when the pain stabbed harder.  Then, automatically, I got the laudanum and went back to her.

It was fully a half-hour before Liddy’s groans subsided.  At intervals I went to the door into the hall and looked out, but I saw and heard nothing suspicious.  Finally, when Liddy had dropped into a doze, I even ventured as far as the head of the circular staircase, but there floated up to me only the even breathing of Winters, the night detective, sleeping just inside the entry.  And then, far off, I heard the rapping noise that had lured Louise down the staircase that other night, two weeks before.  It was over my head, and very faint—­three or four short muffled taps, a pause, and then again, stealthily repeated.

The sound of Mr. Winters’ breathing was comforting; with the thought that there was help within call, something kept me from waking him.  I did not move for a moment; ridiculous things Liddy had said about a ghost—­I am not at all superstitious, except, perhaps, in the middle of the night, with everything dark—­things like that came back to me.  Almost beside me was the clothes chute.  I could feel it, but I could see nothing.  As I stood, listening intently, I heard a sound near me.  It was vague, indefinite.  Then it ceased; there was an uneasy movement and a grunt from the foot of the circular staircase, and silence again.

I stood perfectly still, hardly daring to breathe.

Then I knew I had been right.  Some one was stealthily-passing the head of the staircase and coming toward me in the dark.  I leaned against the wall for support—­my knees were giving way.  The steps were close now, and suddenly I thought of Gertrude.  Of course it was Gertrude.  I put out one hand in front of me, but I touched nothing.  My voice almost refused me, but I managed to gasp out, “Gertrude!”