"You've known Professor Greer a long time?" I asked the white-headed man. "Several years, sir," was his quick reply. "And do you recognise this gentleman as the Professor?" I asked. "Certainly, sir; I saw him pass in at the gate this morning. He's cut off his beard, and that makes a bit of difference to a man, you know!" He laughed. "You have no hesitation in identifying him, eh?" I asked. "You'll be able to swear to him in a court of law?" "Yes, sir, in any court of law. The Professor's been very kind to me, once or twice; therefore it isn't likely that I forget either his face or his voice." This bewildered me. Was it possible that this impostor was the Professor's twin brother? I felt confident that Kirk was continuing some very ingenious conspiracy. Was not his suggestion to me that I should forget the tragedy sufficient proof of double dealing? I thanked the park-keeper, who withdrew with Antonio, whereupon Kirk asked me whether I was not satisfied. "No," I said, "and I shall never be satisfied until I discover the identity of the man who killed Professor Greer." "But Professor Greer stands before you!" declared Ethelwynn; "nobody killed him!" "So you wish me to believe," I said with a smile, "but as my secrecy has been demanded on your account, I can only suspect that you were, in some way, implicated in the crime." She went pale as death. My words, I saw, had a startling effect upon her. She looked first at Kirk and then at the man posing as her father--the man who had secured many thousands of pounds for a secret that was not his own. "Then you refuse to accept even the park-keeper's testimony?" Kirk remarked, while the man who had assumed the Professor's identity walked across to the writing-table and began looking at some letters lying upon it. "I do; my intention is to unmask you all!" The impostor, the fading light falling upon his clear-cut countenance, turned quickly, and upon his face rested an expression of deadly fear that I had not previously noticed. Hitherto his attitude had been one of bold unconcern. But now, realising my determination, he had grown alarmed. He saw that he had carried the imposture too far. "Ethelwynn," he said, in a low, strained voice, "I--I wish to speak with Mr. Holford. Will you leave us for a little while, dear. Go into the Red Room, and we'll join you there later." "My dear sir," I exclaimed, "I don't desire to hear any more of your denials." "I'll go, dad, of course," replied the girl, who, in obedience with his suggestion, left the room. I turned to follow her, but with a sudden movement he placed himself before the door, exclaiming anxiously: "Mr. Holford, pray hear me for one moment, I beg of you. I want to tell you something--to confess!" "Ah!" I laughed triumphantly. "At last! you will confess! Good! I am all attention."