"Having summoned the servants, I ran into the study. But there was absolutely nothing unusual to be seen. The windows were closed and fastened. He worked with closed windows in the hottest weather. There is no other door, for the study occupies the end of a narrow wing, so that no one could possibly have gained access to it, whilst I was in the library, unseen by me. Had someone concealed himself in the study earlier in the evening--and I am convinced that it offers no hiding-place--he could only have come out again by passing through here." Nayland Smith tugged at the lobe of his left ear, as was his habit when meditating. "You had been at work here in this way for some time?" "Yes. Sir Crichton was preparing an important book." "Had anything unusual occurred prior to this evening?" "Yes," said Mr. Burboyne, with evident perplexity; "though I attached no importance to it at the time. Three nights ago Sir Crichton came out to me, and appeared very nervous; but at times his nerves--you know? Well, on this occasion he asked me to search the study. He had an idea that something was concealed there." "Some THING or someone?" "'Something' was the word he used. I searched, but fruitlessly, and he seemed quite satisfied, and returned to his work." "Thank you, Mr. Burboyne. My friend and I would like a few minutes' private investigation in the study." CHAPTER II SIR CRICHTON DAVEY'S study was a small one, and a glance sufficed to show that, as the secretary had said, it offered no hiding-place. It was heavily carpeted, and over-full of Burmese and Chinese ornaments and curios, and upon the mantelpiece stood several framed photographs which showed this to be the sanctum of a wealthy bachelor who was no misogynist. A map of the Indian Empire occupied the larger part of one wall. The grate was empty, for the weather was extremely warm, and a green-shaded lamp on the littered writing-table afforded the only light. The air was stale, for both windows were closed and fastened. Smith immediately pounced upon a large, square envelope that lay beside the blotting-pad. Sir Crichton had not even troubled to open it, but my friend did so. It contained a blank sheet of paper! "Smell!" he directed, handing the letter to me. I raised it to my nostrils. It was scented with some pungent perfume. "What is it?" I asked. "It is a rather rare essential oil," was the reply, "which I have met with before, though never in Europe. I begin to understand, Petrie." He tilted the lamp-shade and made a close examination of the scraps of paper, matches, and other debris that lay in the grate and on the hearth. I took up a copper vase from the mantelpiece, and was examining it curiously, when he turned, a strange expression upon his face. "Put that back, old man," he said quietly. Much surprised, I did as he directed. "Don't touch anything in the room. It may be dangerous."