"Well," he said, glancing at his watch, "the place has not been touched. If you consent to help me, it would be best that you saw it and formed your own independent theory. Would you care to come with me now? You could run along and make some excuse to Mrs. Holford." The remarkable mystery, surrounding as it did one of the best-known scientists in the land, had already gripped my senses. Therefore I did as he suggested, and about an hour later alighted from one of my own cars at the portico of that house of tragedy. A white-faced, grave-eyed man in black, the man Antonio, opened the door in response to our ring, but on recognising my companion he gripped him quickly by the arm, gasping: "Ah, signore, I had just telephoned to you! I had no idea you were returning here to-night. Madonna Santa, signore, it's terrible-- terrible! Something else has happened. The young lady--she's--" "What do you mean? What has happened now?" asked Kirk quickly. "Tell me; she's--what?" But the old Italian could not speak, so overcome and scared was he. He only pulled my companion forward into the dining-room on the left, and with his thin, bony finger pointed within. And as I entered the big room my eyes fell upon a sight that staggered me. Like the old servant, I, too, stood aghast. Truly Kershaw Kirk had spoken the truth when he had said that the mystery was no ordinary one. At that moment the problem seemed to me to be beyond solution. It already ranked in my mind as one of those mysteries to which the key is never discovered. Who _did_ kill Professor Greer? CHAPTER THREE. THE HOUSE OF MYSTERY. What I saw in the house of Professor Greer on the night of that fifteenth of January formed indeed a strange and startling spectacle. Ah, I am haunted by it even now! That sallow-faced man who had conducted me there was himself a mystery, and upon his own confession was suspected of a foul crime. Besides, it was being kept rigorously from the police, which, to say the least, was a proceeding most unusual. What could it all mean? Who was this Kershaw Kirk, this "dealer in secrets," as he called himself, who was immune from public trial, even though not immune from arrest and imprisonment? The whole intricate problem launched upon me during those past few hours held me in fascination as nothing had ever held me before. I could see that the man Antonio held Mr. Kirk in great fear or great regard, for he was urbanity itself.