Oakes stood at the window, his hands in his pockets, looking out.
"Did you see that wall being built yourself, Cook?"
"I didn't notice particularly, sir."
"Well, Stone, we'll try the simplest theory first. Will you kindly go with Cook up to the roof and look around carefully. I have an idea that the wall is double, and that you will find an opening up there somewhere."
We went, and, as Oakes had surmised, soon found a small opening like a chimney, grated in solidly and protected by a covering, and so reported.
"Good!" said Oakes. "The wall is double—in part at least—and the opening was carried into the cellar room and a door placed there."
"What for?" said I.
"Perhaps to ventilate it. We may find some other reason."
"We seem to be solving the mystery," was Moore's comment.