entirely fresh line of investigation. I was shaving at my window inthe morning when I heard the rattle of hoofs and, looking up, saw adog-cart coming at a gallop down the road. It pulled up at our door,and our friend, the vicar, sprang from it and rushed up our gardenpath. Holmes was already dressed, and we hastened down to meet him.

  Our visitor was so excited that he could hardly articulate, but at lastin gasps and bursts his tragic story came out of him.

  "We are devil-ridden, Mr. Holmes! My poor parish is devil-ridden!" hecried. "Satan himself is loose in it! We are given over into hishands!" He danced about in his agitation, a ludicrous object if itwere not for his ashy face and startled eyes. Finally he shot out histerrible news.

  "Mr. Mortimer Tregennis died during the night, and with exactly thesame symptoms as the rest of his family."

  Holmes sprang to his feet, all energy in an instant.

  "Can you fit us both into your dog-cart?"

  "Yes, I can."

  "Then, Watson, we will postpone our breakfast. Mr. Roundhay, we areentirely at your disposal. Hurry--hurry, before things getdisarranged."

  The lodger occupied two rooms at the vicarage, which were in an angleby themselves, the one above the other. Below was a largesitting-room; above, his bedroom. They looked out upon a croquet lawnwhich came up to the windows. We had arrived before the doctor or thepolice, so that everything was absolutely undisturbed. Let me describeexactly the scene as we saw it upon that misty March morning. It hasleft an impression which can never be effaced from my mind.

  The atmosphere of the room was of a horrible and depressing stuffiness.The servant who had first entered had thrown up the window, or it wouldhave been even more intolerable. This might partly be due to the factthat a lamp stood flaring and smoking on the centre table. Beside itsat the dead man, leaning back in his chair, his thin beard projecting,his spectacles pushed up on to his forehead, and his lean dark faceturned towards the window and twisted into the same distortion ofterror which had marked the features of his dead sister. His limbswere convulsed and his fingers contorted as though he had died in avery paroxysm of fear. He was fully clothed, though there were signsthat his dressing had been done in a hurry. We had already learnedthat his bed had been slept in, and that the tragic end had come to himin the early morning.

  One realized the red-hot energy which underlay Holmes's phlegmaticexterior when one saw the sudden change which came over him from themoment that he entered the fatal apartment. In an instant he was tenseand alert, his eyes shining, his face set, his limbs quivering witheager activity. He was out on the lawn, in through the window, roundthe room, and up into the bedroom, for all the world like a dashingfoxhound drawing a cover. In the bedroom he made a rapid cast aroundand ended by throwing open the window, which appeared to give him somefresh cause for excitement, for he leaned out of it with loudejaculations of interest and delight. Then he rushed down the stair,out through the open window, threw himself upon his face on the lawn,sprang up and into the room once more, all with the energy of thehunter who is at the very heels of his quarry. The lamp, which was anordinary standard, he examined with minute care, making certainmeasurements upon its bowl. He carefully scrutinized with his lens thetalc shield which covered the top of the chimney and scraped off someashes which adhered to its upper surface, putting some of them into anenvelope, which he placed in his pocketbook. Finally, just as thedoctor and the official police put in an appearance, he beckoned to thevicar and we all three went out upon the lawn.

  "I am glad to say that my investigation has not been entirely barren,"he remarked. "I cannot remain to discuss the matter with the police,but I should be exceedingly obliged, Mr. Roundhay, if you would givethe inspector my compliments and direct his attention to the bedroomwindow and to the sitting-room lamp. Each is suggestive, and togetherthey are almost conclusive. If the police would desire furtherinformation I shall be happy to see any of them at the cottage. Andnow, Watson, I think that, perhaps, we shall be better employedelsewhere."

  It may be that the police resented the intrusion of an amateur, or thatthey imagined themselves to be upon some hopeful line of investigation;but it is certain that we heard nothing from them for the next twodays. During this time Holmes spent some of his time smoking anddreaming in the cottage; but a greater portion in country walks whichhe undertook alone, returning after many hours without remark as towhere he had been. One experiment served to show me the line of hisinvestigation. He had bought a lamp which was the duplicate of the onewhich had burned in the room of Mortimer Tregennis on the morning ofthe tragedy. This he filled with the same oil as that used at thevicarage, and he carefully timed the period which it would take to beexhausted. Another experiment which he made was of a more unpleasantnature, and one which I am not likely ever to forget.

  "You will remember, Watson," he remarked one afternoon, "that there isa single common point of resemblance in the varying reports which havereached us. This concerns the effect of the atmosphere of the room ineach case upon those who had first entered it. You will recollect thatMortimer Tregennis, in describing the episode of his last visit to hisbrother's house, remarked that the doctor on entering the room fellinto a chair? You had forgotten? Well I can answer for it that it wasso. Now, you will remember also that Mrs. Porter, the housekeeper, toldus that she herself fainted upon entering the room and had afterwardsopened the window. In the second case--that of Mortimer Tregennishimself--you cannot have forgotten the horrible stuffiness of the roomwhen we arrived, though the servant had thrown open the window. Thatservant, I found upon inquiry, was so ill that she had gone to her bed.You will admit, Watson, that these facts are very suggestive. In eachcase there is evidence of a poisonous atmosphere. In each case, also,there is combustion going on in the room--in the one case a fire, inthe other a lamp. The fire was needed, but the lamp was lit--as acomparison of the oil consumed will show--long after it was broaddaylight. Why? Surely because there is some connection between threethings--the burning, the stuffy atmosphere, and, finally, the madnessor death of those unfortunate people. That is clear, is it not?"

  "It would appear so."

  "At least we may accept it as a working hypothesis. We will suppose,then, that something was burned in each case which produced anatmosphere causing strange toxic effects. Very good. In the firstinstance--that of the Tregennis family--this substance was placed inthe fire. Now the window was shut, but the fire would naturally carryfumes to some extent up the chimney. Hence one would expect theeffects of the poison to be less than in the second case, where therewas less escape for the vapour. The result seems to indicate that itwas so, since in the first case only the woman, who had presumably themore sensitive organism, was killed, the others exhibiting thattemporary or permanent lunacy which is evidently the first effect ofthe drug. In the second case the result was complete. The facts,therefore, seem to bear out the theory of a poison which worked bycombustion.

  "With this train of reasoning in my head I naturally looked about inMortimer Tregennis's room to find some remains of this substance. Theobvious place to look was the talc shelf or smoke-guard of the lamp.There, sure enough, I perceived a number of flaky ashes, and round theedges a fringe of brownish powder, which had not yet been consumed.Half of this I took, as you saw, and I placed it in an envelope."

  "Why half, Holmes?"

  "It is not for me, my dear Watson, to stand in the way of the officialpolice force. I leave them all the evidence which I found. The poisonstill remained upon the talc had they the wit to find it. Now, Watson,we will light our lamp; we will, however, take the precaution to openour window to avoid the premature decease of two deserving members ofsociety, and you will seat yourself near that open window in anarmchair unless, like a sensible man, you determine to have nothing todo with the affair. Oh, you will see it out, will you? I thought Iknew my Watson. This chair I will place opposite yours, so that we maybe the same distance from the poison and face to face. The door wewi
ll leave ajar. Each is now in a position to watch the other and tobring the experiment to an end should the symptoms seem alarming. Isthat all clear? Well, then, I take our powder--or what remains ofit--from the envelope, and I lay it above the burning lamp. So! Now,Watson, let us sit down and await developments."

  They were not long in coming. I had hardly settled in my chair beforeI was conscious of a thick, musky odour, subtle and nauseous. At thevery first whiff of it my brain and my imagination were beyond allcontrol. A thick, black cloud swirled before my eyes, and my mind toldme that in this cloud, unseen as yet, but about to spring out upon myappalled senses, lurked all that was vaguely horrible, all that wasmonstrous and inconceivably wicked in the universe. Vague shapesswirled and swam amid the dark cloud-bank, each a menace and a warningof something coming, the advent of some unspeakable dweller upon