Thorndyke listened from the very beginning of my story with the closest attention. His face was the most impassive that I have ever seen; ordinarily as inscrutable as a bronze mask; but to me, who knew him intimately, there was a certain something—a change of color, perhaps, or an additional sparkle of the eye—that told me when his curious passion for investigation was fully aroused. And now, as I told him of that weird journey and the strange, secret house to which it had brought me, I could see that it offered a problem after his very heart. During the whole of my narration he sat as motionless as a statue, evidently committing the whole story to memory, detail by detail; and even when I had finished he remained for an appreciable time without moving or speaking.
At length he looked up at me. "This is a very extraordinary affair, Jervis," he said.
"Very," I agreed; "and the question that is agitating me is, what is to be done?"
"Yes," he said, meditatively, "that is the question; and an uncommonly difficult question it is. It really involves the settlement of the antecedent question: What is it that is happening at that house?"
"What do you think is happening at that house?" I asked.
"We must go slow, Jervis," he replied. "We must carefully separate the legal tissues from the medical, and avoid confusing what we know with what we suspect. Now, with reference to the
