"And only for that reason?" I queried. He hesitated. "Well--and for another--another which must remain a confidential matter with myself," he replied at length. "The Professor was in possession of a certain secret, and my belief is that this secret was stolen from him and his mouth afterwards closed by the thief." "Why?" "Because, had the unfortunate man spoken, certain complications, very serious complications, involving huge losses, would have accrued. So there was only one way--to kill poor Greer! But the manner in which this was accomplished is still an absolute enigma." "Has it not struck you that the telegram sent from Edinburgh may have been despatched by the assassin?" I asked. But he was uncertain. He had as yet, he said, formed no theory as to that portion of the problem. "Where is the unfortunate girl?" I asked, for I had noticed that she was not in the dining-room. He looked at me quickly, with a strange expression in his peculiar eyes. "She's still here, of course," he declared. "That second phase of the mystery is as complicated as the first--perhaps even more so. Come with me a moment." I followed him through the boudoir and into the study, where, opening a long cupboard in the wall, a small iron safe was revealed, the door of which opened at his touch. "Here," he explained, "the Professor kept the valuable notes upon the results of his experiments. The safe was closed when I first called, but this morning I found it open, and the contents gone!" "Then the person who killed Professor Greer was not the thief!" I remarked. "Unless he returned here afterwards," was Kirk's reply, with his eyes fixed upon mine. Then he glanced at his watch, and without a word turned upon his heel and passed out of the room. CHAPTER SIX. A FURTHER MYSTERY. I stood awaiting his return for a few moments, and then followed him out upon the landing, where my feet fell noiselessly upon the thick Turkey carpet. Almost opposite, across the open staircase, I could see into the large drawing-room, and there, to my amazement, I saw Kirk raising and lowering one of the blinds. He was making the same signal to someone outside in the park as that made by the Professor before his death! I slipped back to the study, much puzzled, but in a few moments he returned, smiling and affable. What signal had he made--and to whom? It was foggy outside, therefore the watcher must have been in the close vicinity. Antonio appeared at the door, whereupon Kirk gave the manservant certain instructions regarding the payment and discharge of the servants. Apparently one of them had returned and asked for her wages in lieu of notice. "Be liberal with them," urged my companion. "We don't want any grumbling. There is no suspicion as yet, and liberality will disarm it." "Very well, signore," replied the man, "I will pay them all and get rid of them as soon as possible." "Yes, at once," Kirk snapped, and the man went down the stairs.