"Any windows on this side?"
"No."
"Just as I thought. There is a room above that vault. We'll try the second floor. I trust we are not too late," he added as we returned to the study. There we waited while McKelvie relocked the entrance, and when he was ready to lead the way upstairs again, Jones spoke in a troubled whisper.
"What's the idea of building a house with holes in the wall? It's a regular rat-trap," he said.
"I have a book at home that I'll have to lend you, Jones. The man who built this house was a nut on old-fashioned ideas. He copied an ancestral home, secret rooms and all. Not that he meant to use them, of course, but because it suited him to put them in. The one I just examined was used in ancient times, I think, to receive the bodies of those who fell through the trap door from the room above. A convenient way of getting rid of your enemy, that is all."
"This criminal of yours seems very familiar with this house," said Jones.
"Yes, he had been here many times before the murder, and he took pains to learn all he could about the place," returned McKelvie.
"I thought he only learned of the entrance on the night of the murder," I objected.
"Well, what of it. He is clever enough to have deduced what I did. He probably stumbled across the lower room in opening the outer door and then it was mere child's play to discover the room above."
Yes, that part was easy enough, but it was another matter to find the hidden spring that worked the panel. We turned on the light in the room, and divided the wall into three parts, each of us fingering a third carefully and painstakingly from top to bottom. It was Jones finally who stumbled on the spring. He had pressed the center of one of the mahogany flowers that formed the carved border of the dash-board and silently the panel slid back.