felt convinced that he would be. It was obvious to me when I first heard your story that the pledge of secrecy you extracted from Miss Ches worth upon leaving Charmingdene came too late.
"Naturally she or her brother had already, in all innocence, told the doctor they had confided in you and that you had proffered your help. You had no suspicion of Penhryn yourself; it was the colonel you wanted to guard against. But Penhryn immediately saw the danger of your continued presence at Charmingdene. You were a dangerous obstacle to the fulfilment of his plans, and he decided to have you out of the way.
"He must have brought Colonel Gravenall back from London by some specious telegram and persuaded him to discharge you; there can be little doubt of that. And when you were discharged he wanted to be sure that you returned to London, for had you remained in Cornwall it was clear proof that you were still on the watch."
Sudden enlightenment dawned upon me. "So that accounts for St. Odd and the ticket to London?" I said.
Grey gave a slight shrug.
"Yes, for I felt quite certain Penhryn would proceed with his experiments more freely and rapidly if he saw you in the train. I was right. From a place of concealment I observed him go through the barrier and walk quickly up the platform, scrutinizing the interior of the carriages as he went. When he saw you seated in an empty compartment, reading, he was satisfied, and immediately turned away, leaving the station as quickly as he could. I followed him through the barrier just in time to see him step into his small ear outside, and drive off along the road which leads across the moors.
"I followed him in my own car at a safe distance, until I saw him drive past his own house and go on towards Charmingdene, as I supposed. Extinguishing the lights of my car, I left it upon the moors while I forced an entry into this place. Penhryn might have returned and found me there, but that was a risk I had to take. I did not fear it very much, nevertheless. If my reading of the case was correct, Penhryn needed another night with his unhappy patient at Charmingdene to prepare him by baleful 'suggestions' for the final beating of his sinister drum. And I was right in that conjecture, as we have seen.
"In this room I found his writing cabinet, which I managed without, using force to unlock, and proceeded to examine its contents. In the secret drawer were these documents and the locked diary, which I opened and proceeded to read. In them the fantastic experiments of an unbalanced brain were set down in his hand, plain to read. And although I have read that strange confession with my own eyes, I remain incredulous still. Even now I ask myself if it can be true.
"After reading and replacing these extraordinary notes, I made further search of the house. At the bottom of a box of curios upstairs I found a small native tom-tom or drum. And with that symbol the proofs of his guilt were complete.
"I might have waited and confronted him with these things, but a moment's reflection persuaded me of the unwisdom of that. How far had he transgressed the law? In what way could the law lay hold upon him for what he had done? Without going into that question, I decided upon a better and surer way, which was to surprise him while he was engaged in his final design.
"After you left me yesterday I walked back across the cliffs to the old mining hut, and waited quietly in its vicinity until night. I had brought sandwiches and a flask, and the time passed quickly enough. I knew Dr. Penhryn would not come until late, but I feared Edward Chesworth might, and I did not wish to take any risk on that score. But the last stage of this bizarre affair worked out as planned—up to a point.
■ "About half-past ten I heard the throbbing of a motor car on the road to the cliff, and a few minutes later my ears caught the sound of approaching footsteps on the echoing rocks. It was Pen-
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