That was Louise’s story.  There could be no doubt of its truth, and the thing that made it inexpressibly awful to me was that the poor girl had crept down to answer the summons of a brother who would never need her kindly offices again.  Twice now, without apparent cause, some one had entered the house by means of the east entrance:  had apparently gone his way unhindered through the house, and gone out again as he had entered.  Had this unknown visitor been there a third time, the night Arnold Armstrong was murdered?  Or a fourth, the time Mr. Jamieson had locked some one in the clothes chute?

Sleep was impossible, I think, for any of us.  We dispersed finally to bathe and dress, leaving Louise little the worse for her experience.  But I determined that before the day was over she must know the true state of affairs.  Another decision I made, and I put it into execution immediately after breakfast.  I had one of the unused bedrooms in the east wing, back along the small corridor, prepared for occupancy, and from that time on, Alex, the gardener, slept there.  One man in that barn of a house was an absurdity, with things happening all the time, and I must say that Alex was as unobjectionable as any one could possibly have been.

The next morning, also, Halsey and I made an exhaustive examination of the circular staircase, the small entry at its foot, and the card-room opening from it.  There was no evidence of anything unusual the night before, and had we not ourselves heard the rapping noises, I should have felt that Louise’s imagination had run away with her.  The outer door was closed and locked, and the staircase curved above us, for all the world like any other staircase.

Halsey, who had never taken seriously my account of the night Liddy and I were there alone, was grave enough now.  He examined the paneling of the wainscoting above and below the stairs, evidently looking for a secret door, and suddenly there flashed into my mind the recollection of a scrap of paper that Mr. Jamieson had found among Arnold Armstrong’s effects.  As nearly as possible I repeated its contents to him, while Halsey took them down in a note-book.

“I wish you had told me that before,” he said, as he put the memorandum carefully away.  We found nothing at all in the house, and I expected little from any examination of the porch and grounds.  But as we opened the outer door something fell into the entry with a clatter.  It was a cue from the billiard-room.

Halsey picked it up with an exclamation.

“That’s careless enough,” he said.  “Some of the servants have been amusing themselves.”

I was far from convinced.  Not one of the servants would go into that wing at night unless driven by dire necessity.  And a billiard cue!  As a weapon of either offense or defense it was an absurdity, unless one accepted Liddy’s hypothesis of a ghost, and even then, as Halsey pointed out, a billiard-playing ghost would be a very modern evolution of an ancient institution.