in my own mind I had fondly imagined I should
discover the secret chamber without much difficulty, but soon I began
to realize that it was not such an easy task as I had expected, and at
the end of a couple of hours I came near to owning myself beaten.

"This is where I saw old Denny sounding the walls with the hammer,"
said Miles. As my companion spoke, we were passing down the narrow
wainscoted passage which he had described to me at school. I struck
the boarding myself once or twice with my knuckles as we moved along,
but produced no sound which might betoken the presence of a hollow
cavity behind the oak. Arriving at length at an old square-panelled
doorway, we entered a room which I at once realized I had not been
inside before. Save for a plain wooden chair and table, it was empty
and destitute of furniture. There was nothing specially remarkable
about the place, yet the appearance of its interior seems so vividly
impressed on my mind, that I can see it now as though at this moment I
were once more crossing the threshold.

The apartment was evidently intended for a sort of morning room or
second parlour. The walls were panelled with oak, and a carved
mantelpiece, of massive though not elaborate design, framed the wide,
open hearth. There was a curious earthy smell about the place,
probably owing to the fact that it was never used; which seemed
strange, for it had a pleasant outlook into the garden.

"What a jolly room!" I exclaimed. "Why isn't it used?"

Miles gave a short laugh.

"There's no need," he answered; "we've got enough without it."

We crossed the bare floor and sat down in the deep window-seat. I
still went on talking, but, though I hardly noticed it at the time, my
companion grew quieter than before. He returned absent-minded replies
to my questions, and seemed, from the position of his head, as though
he half expected to hear something in the passage or the garden. We
may have sat like this for ten minutes or longer, when suddenly an
intent expression on Miles's face caused me to break off abruptly in
what I was saying. Then, for the first time, I became aware of a
curious sound, faint and subdued, as though some one were humming with
the mouth closed. At first it seemed far away; then it might have been
in the room, though in what part it was impossible to say. I was
listening idly and with no particular wonder to the noise, when Miles
rose to his feet.

"Come on," he said abr