One realised the red-hot energy which underlay Holmes’s phlegmatic exterior when one saw the sudden change which came over him from the moment that he entered the fatal apartment. In an instant he was tense and alert, his eyes shining, his face set, his limbs quivering with eager activity. He was out on the lawn, in through the window, round the room, and up into the bedroom, for all the world like a dashing foxhound drawing a cover. In the bedroom he made a rapid cast around, and ended by throwing open the window, which appeared to give him some fresh cause for excitement, for he leaned out of it with loud ejaculations 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 the hunter who is at the very heels of his quarry. The lamp, which was an ordinary standard, he examined with minute care, making certain measurements upon its bowl. He carefully scrutinized with his lens the talc shield which covered the top of the chimney, and scraped off some ashes which adhered to its upper surface, putting some of them into an envelope, which he placed in his pocket- book. Finally, just as the doctor and the official police put in an appearance, he beckoned to the vicar 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 give the inspector my compliments and direct his attention to the bedroom window and to the sitting-room lamp. Each is suggestive, and together they are almost conclusive. If the police would desire further information I shall be happy to see any of them at the cottage. And now, Watson, I think that, perhaps, we shall be better employed elsewhere.’
It may be that the police resented the intrusion of an amateur, or that they imagined themselves to be upon some hopeful line of investigation; but it is certain that we heard nothing from them for the next two days. During this time Holmes spent some of his time smoking and dreaming in the cottage; but a greater portion in country walks which he undertook alone, returning after many hours without remark as to where he had been. One experiment served to show me the line of his investigation. He had bought a lamp which was the duplicate of the one which had burned in the room of Mortimer Tregennis on the morning of the tragedy. This he filled with the same oil as that used at the vicarage, and he carefully timed the period which it would take to be exhausted. Another experiment which he made was of a more unpleasant nature, and one which I am not likely ever to forget.
‘You will remember, Watson,’ he remarked one afternoon, ‘that there is a single common point of resemblance in the varying reports which have reached us. This concerns the effect of the atmosphere of the room in each case upon those who had first entered it. You will recollect that Mortimer Tregennis, in describing the episode of his last visit to his brothers’ house, remarked that the doctor on entering the room fell into a chair? You had forgotten? Well, I can answer for it that it was so. Now, you will remember also that Mrs Porter, the housekeeper, told us that she herself fainted upon entering the room and had afterwards opened the window. In the second case—that of Mortimer Tregennis himself—you cannot have forgotten the horrible stuffiness of the room when we arrived, though the servant had thrown open the window. That servant, 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 each case, 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, in the other a lamp. The fire was needed, but the lamp was lit—as a comparison of the oil consumed will show—long after it was broad daylight. Why? Surely because there is some connection between three things—the burning, the stuffy atmosphere, and, finally, the madness or 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 an atmosphere causing strange toxic effects. Very good. In the first instance—that of the Tregennis family—this substance was placed in the fire. Now the window was shut, but the fire would naturally carry fumes to some extent up the chimney. Hence one would expect the effects