"No, I will swear to his sanity."
"Have you any other theory?"
"Well, yourself, for example. You are not a somnambulist, by any chance?"
"Nothing of the sort, I assure you."
"Then I give it up."
"But I don't—and I have a plan by which we will make it all clear."
"To visit Professor Andreas?"
"No, we shall find our solution nearer than Scotland. I will tell you what we shall do. You know that skylight which overlooks the central hall? We will leave the electric lights in the hall, and we will keep watch in the lumber-room, you and I, and solve the mystery for ourselves. If our mysterious visitor is doing four stones at a time, he has four still to do, and there is every reason to think that he will return tonight and complete the job."
"Excellent!" I cried.
"We will keep our own secret, and say nothing either to the police or to Simpson. Will you join me?"