“Nonsense!” I said.  “Plaster is always falling.”

But Liddy clenched that.

“Just ask Alex,” she said.  “When he put the new cook’s trunk there last night the wall was as smooth as this.  This morning it’s dug out, and there’s plaster on the cook’s trunk.  Miss Rachel, you can get a dozen detectives and put one on every stair in the house, and you’ll never catch anything.  There’s some things you can’t handcuff.”

Liddy was right.  As soon as I could, I went up to the trunk-room, which was directly over my bedroom.  The plan of the upper story of the house was like that of the second floor, in the main.  One end, however, over the east wing, had been left only roughly finished, the intention having been to convert it into a ball-room at some future time.  The maids’ rooms, trunk-room, and various store-rooms, including a large airy linen-room, opened from a long corridor, like that on the second floor.  And in the trunk-room, as Liddy had said, was a fresh break in the plaster.

Not only in the plaster, but through the lathing, the aperture extended.  I reached into the opening, and three feet away, perhaps, I could touch the bricks of the partition wall.  For some reason, the architect, in building the house, had left a space there that struck me, even in the surprise of the discovery, as an excellent place for a conflagration to gain headway.

“You are sure the hole was not here yesterday?” I asked Liddy, whose expression was a mixture of satisfaction and alarm.  In answer she pointed to the new cook’s trunk—­that necessary adjunct of the migratory domestic.  The top was covered with fine white plaster, as was the floor.  But there were no large pieces of mortar lying around—­no bits of lathing.  When I mentioned this to Liddy she merely raised her eyebrows.  Being quite confident that the gap was of unholy origin, she did not concern herself with such trifles as a bit of mortar and lath.  No doubt they were even then heaped neatly on a gravestone in the Casanova churchyard!

I brought Mr. Jamieson up to see the hole in the wall, directly after breakfast.  His expression was very odd when he looked at it, and the first thing he did was to try to discover what object, if any, such a hole could have.  He got a piece of candle, and by enlarging the aperture a little was able to examine what lay beyond.  The result was nil.  The trunk-room, although heated by steam heat, like the rest of the house, boasted of a fireplace and mantel as well.  The opening had been made between the flue and the outer wall of the house.  There was revealed, however, on inspection, only the brick of the chimney on one side and the outer wall of the house on the other; in depth the space extended only to the flooring.  The breach had been made about four feet from the floor, and inside were all the missing bits of plaster.  It had been a methodical ghost.