It was a little later, when we came to speak of the optophone, that I found him to be still firmly rooted in the conviction that Esdaile's cellar contained the solution of at least a portion of our mystery. He was quite unshakable on this point. I will not trouble to re-state his recapitulation of the events of the morning of the farewell breakfast. Of subsequent events, I may say, he knew little.

"Well, I won't pretend to understand you," I said at last. "If you seriously think that Esdaile's got some sort of an optophone in his house——"

He waved his hand impatiently, as if to beg of me not to be an ass.

"Oh, cut that out. I'm not given to melodrama any more than you are. Of course he hasn't; that's infantile. But what is there to prevent there being something peculiar about the ordinary acoustics of the place—perfectly ordinarily and naturally, but one of these freakish effects—there are such things—an echo's the commonest example, of course—then there are these whispering effects—vagaries of sound——" He tailed off.

"But he heard no sound," I objected, "or at any rate so little that we decided he couldn't know what it was. He certainly didn't hear what we heard. You've got the whole thing turned round."

"I know," he mused. "And yet he gave you the impression of a man who knew more than all the rest of us put together. In fact, he practically admitted he did."

"But—if you will have it it's the cellar—two people have been down since."

He turned quickly. "Who are they?"

"Rooke and Mrs. Cunningham."

"Well, and what had they to say about it?"

I had to admit that, according to Rooke, something about the place had brought Mrs. Cunningham to the verge of hysteria, while Rooke himself had found the place inexplicably uncanny.

"Then as far as it goes that bears me out?"

"As far as it goes. But they found nothing out of the ordinary. Esdaile even left the key in the door, and there was nothing to prevent them from rummaging to their hearts' content."

"Did they rummage?"

"Rooke didn't. Said he wasn't a policeman to go scratching about other people's houses. I thought it rather decent of him."

"Well—it's possible they didn't know what to look for."

"Do you?" I parried.

"No," he confessed,—"not unless he keeps a tame ghost down there."

"In that case the Chelsea Arts Club would be right," I laughed; and we went on to speak of other things.