I do not know just what my auditors expected in the way of an explanation of the mystery when they followed me to the green room—possibly some well-constructed or finely drawn theory. When I pointed to the chandelier, they all looked a bit nonplused, and nobody said anything for several moments. Then McQuade remarked, in his quiet voice, with a shade of comprehension in his tone and expression: "How do you make that out, Sir?"

The chandelier to which I had pointed was an old-fashioned one, of the kind in general use in the early fifties. It was, I fancied, originally made for a room with a somewhat higher ceiling. The ceilings in the wings of The Oaks were unusually low, and the extreme lower end of the chandelier extended to a point not much over six feet from the floor. I judged this, because I am myself five feet eleven, and I could just pass beneath it without striking it. It hung in the center of the room, and about three feet from the side of the bed, which, on account of its great size, extended far out from the wall against which it was placed. The chandelier was of dark bronze or bronzed iron, and consisted of a heavy central stem, from the lower end of which extended four elaborately carved branches, supported by heavy and useless chains reaching to a large ball about midway up the stem. Below the point from which these four arms sprung was a sort of circular bronze shield, or target, and from the lower face of this, in the center, projected an octagonal ornamental spike, about two and a half inches long, terminating in a sharp point. The whole thing was ugly and heavy, and seemed in design more suitable to a hall or library than a bedroom. Almost directly beneath it, but somewhat nearer to the side of the bed, stood the low bench or stool, not over five inches high, the use of which I have already mentioned. I explained the tragedy to the detective and the others as I knew it must have happened.

"Last night," I said, "I was unable to open either the window in the south or that in the west wall, because of the driving rain. The same conditions, as you will remember, existed upon the fatal night which Mr. Ashton spent here. For some reason, which I hope to explain presently, we were both nearly suffocated while asleep, and rose suddenly in bed, with but one thought, one desire, to get a breath of fresh air. The window in the west wall, directly opposite the bed, attracted us. In Mr. Ashton's case, no doubt, the face of Li Min, peering in from without, increased his terror. Like myself, he sprang up and dashed toward the window, placing his right foot, as I did, upon the low stool beside the bed. His first dash forward and upward, to a standing position, like my own, brought his head, elevated by the height of the stool, in contact with the spike upon the lower end of the chandelier with great force. The spike entered his head, fracturing the skull. He was a taller and heavier man than myself, and the force of the contact as he sprang forward and upward must have been terrific. In my case, owing to my having jumped from the bed at a slightly different point, I struck the spike only a glancing blow, which was sufficient however to render me unconscious for several minutes. I fell to the floor, senseless, but in a short time I struggled to my knees and managed, by crawling painfully to the door, to escape from the room. The interval, from the time I first fell to the time I reached the hall and again became unconscious, must have been very short."

"Why?" asked McQuade, who, like the others, followed my every word with intense interest.

"Because, had the time been very long, I, like Mr. Ashton, should never have risen at all. You would have found me here this morning, as he was found."

"But why?" asked Major Temple.

For answer I took a box of wax tapers from my pocket and lighted one. "Have you ever heard of the Cave of Dogs, near Naples?" I inquired.

"Carbon dioxide," gasped the Major with a look of comprehension.

Sergeant McQuade looked blank, and I saw that to him neither my question nor the Major's answer had conveyed any definite meaning. "Look," I cried, as I held the match out before me, where it burned with a bright, clear flame.

McQuade's mystification increased. I think he wondered if I were trying to play some practical joke upon him. But, when I slowly lowered the taper until it reached a point a few inches above my knee, and its flame faded away and then suddenly went out, as though the match had been plunged into a basin of water, his expression slowly cleared, and he gave a significant grunt. "Carbonic-acid gas," he said. "I understand. But where does it come from?"

"That I do not know, at the moment," I said, "but I think there should be no great difficulty in finding out. This room has been closed for a long time. Even when Mr. Ashton came here, it was opened for only a few moments. Neither he nor I opened the windows, because of the rain, as you know. Somehow, just how I cannot say, a slow stream of carbonic-acid gas finds its way into this room. It is the product of combustion, as you of course know, and is produced in large quantities by burning coal. It may come through the register from the furnace, or from some peculiar action of partially slacked lime in the plaster of the walls. Wherever it comes from, being heavier than air, it slowly settles to the floor, where it collects, becoming deeper and deeper, just as water collects and rises in a tank. Look." I tore a few sheets from the magazine I had been reading the night before, which still lay upon the bed, and lighting them with another match, extinguished the flame, but allowed the smoke from the smoldering paper to spread about the room. It slowly sank until it rested upon the surface of the heavy gas, like a layer of ice upon the surface of a body of water. It showed the carbon dioxide to be considerably over two feet deep, and some six or eight inches below the level of the top of the bed. I knew it must have risen higher during the night, as it was its deadly fumes, closing about my pillow and beginning to enter my lungs, that caused my troubled dreams, as well as, ultimately, the feeling of suffocation which had caused me to awake so suddenly. A considerable portion of the gas had evidently flowed out through the open door, as I lay across the threshold, after my escape from the room.

"And that is what killed poor Boris," said the Major, as he watched the eddying whirls of smoke which settled and rested upon the surface of the gas. "Exactly," I said, "and probably Ashton as well. His skull was fractured, it is true, but the divisional surgeon at the inquest reported, you may remember, that the fracture was not sufficient of itself to have caused instant death. It was ten minutes or more, I should say, from the time I was first awakened by Ashton's cry, until we finally broke in the door and reached his side. By that time he had suffocated. The gas, as no doubt you know, is not a poisonous one, but containing no oxygen which the lungs can take up, acts very much the same as water would if breathed into the lungs."

Muriel looked at me with admiring eyes. I did not tell her that my father had intended me to be, like himself, an engineer, and that I had taken a pretty thorough technical course before adopting art as a profession. And, after all, the simple explanations I had made were known to almost every schoolboy with a little knowledge of chemistry or physics.

"I believe your explanation of Mr. Ashton's death is the correct one, Mr. Morgan," said McQuade, and he said it ungrudgingly. "But how, after all, did the missing emerald come to be found in the cake of soap?"

"Undoubtedly Ashton put it there," I replied. "He realized the enormous value of the thing and feared that some attempt might be made to take it from him. His hiding place for the jewel was certainly an ingenious one, and you will remember that you and your men searched the room thoroughly on more than one occasion without finding it."

McQuade looked a bit sheepish at this. He walked over to the chandelier and examined its ugly-looking spike with deep interest. It was stained with dried blood and a few bits of hair still clung to it, but whether Ashton's or my own, we could of course not tell. There seemed nothing further that we could do, and, as McQuade said he intended going into Exeter immediately after luncheon to make his report, and have the authorities make an examination into the cause of the collection of the carbonic-acid gas in the room, as well as the stains of blood, etc., upon the point of the chandelier, I suggested that I accompany him, as I wanted to get my wound dressed without delay.

We set out, about an hour later, with Gibson and the high cart, and on the way McQuade told me about his attempts to locate the much sought emerald. It seems that after two days of effort his men had located the underground temple of Buddha, but, when they found it, it had been stripped of all its decorations and was merely an old cellar floored over. It appears that the Chinamen, in taking us from the house in Kingsgate street, had passed through an areaway back of the house, and thence through a gateway in the rear wall, into a narrow court, along which they had proceeded some distance. From here they had entered the rear of a house facing upon the adjoining street, to which the cellar belonged. The house had been taken, but a short time before, by a couple of Chinamen who wished to use it as a dwelling. They were seldom seen by the neighbors, and visitors came and went at night, unnoticed by the occupants of the neighboring houses. They had all, however, completely disappeared, and left hardly a trace of their presence. No doubt by now the emerald Buddha was far on its way toward the little shrine in Ping Yang, carefully secreted among the belongings of the old temple priest. I felt a sort of secret satisfaction at learning this, and I think Sergeant McQuade did as well. Certainly it did not belong in this part of the world, and its possession could have brought nothing but trouble and danger to all of us. I think Major Temple was glad, as well, although I never heard him mention the subject of the jewel again. I fancy he felt to some extent responsible for Ashton's death, or at least for having sent him upon the quest which ultimately resulted in it.

I had six stitches taken in my head by an excellent old doctor in town, who tried his best to find out how I had come by such a severe wound, but I refused to satisfy his curiosity, and drove back with Gibson an hour later, after saying good-by to the man from Scotland Yard. He never, to my knowledge visited The Oaks again, although I received a letter from him later, with reference to the investigation which the authorities had made into the cause of the accumulation of the carbonic-acid gas in the room which Ashton and myself had successively occupied with such disastrous results. It seems that the heating system in the house had been installed by its former occupant and owner, a native of Brazil, unused to our cold English winters. It consisted of a series of sheet iron pipes, leading from a large furnace in the cellar. The pipe which supplied the heat for the green room, whether by accident or design, led directly from the combustion chamber of the furnace instead of from a hot-air chamber, as was the case with the other pipes. The consequence was that while the hot air taken to the other rooms was pure air, drawn from without and heated, that which supplied the green room carried away from the furnace great quantities of carbon dioxide, produced in the combustion of the coal. An old valve in the pipe showed that this source of supply could be shut off when so desired, and from this I judged that the owner of the house may have had the piping intentionally so constructed, with the idea of putting out of the way some undesirable friends or relatives. That such was actually the case seemed borne out by the rumors of at least two sudden and mysterious deaths which were known to have occurred in the house. Major Temple, owing to his long residence in India and the East could not endure a cold house, and the presence of this heating plant had been one of the reasons which had governed him in leasing the house for the winter. As far as I was concerned, I had not noticed the register in the wall at all, during the night I slept in the room, having forgotten its existence. I presume it had been turned on by Mr. Ashton. Had I noticed it, I should certainly have turned it off, as I particularly dislike to sleep in a heated room.

I reached the house about four o'clock and found Muriel awaiting my return in the library. Her father, she told me, had gone off for a walk. We had a great deal to say to each other, and it took us till dinner to say it, but I have an idea that it would not interest the reader particularly. We had a lively party at dinner, and the Major got out some special vintage champagne to celebrate our engagement and drink to our future happiness. It was late before I turned in, and I did not, you may be sure, sleep in the green room. The next day, I set out for Torquay by rail, to explain to my mother my long delay in arriving, and to tell her about Muriel. With my departure from The Oaks the story of the emerald Buddha, and the memorable week it caused me, is ended, but the blessings that came to me through it I had only begun to appreciate. I have not become a Buddhist, yet I confess that I never see a statue of that deity but I bend my head before his benign and inscrutable face, and render up thanks for the great blessings he has showered upon me. It has now been three years since Muriel and I were married, and they have been three years of almost perfect happiness. We think of making a trip to China, some of these days, and, if we do, we have concluded to make a special pilgrimage to Ping Yang, and place upon the altar of Buddha the most beautiful bunch of flowers that money can buy, as a little offering and testimonial of our appreciation of what he has done for us.