An hour passed. There had been no repetition of the slight sounds to which I have referred, and the stillness of Low Fennel was really extraordinary. A thermometer, which I had placed upon the table near to my elbow, recorded the fact that the temperature of the room had not abated a fraction of a point since sunset, and, sitting still though I was, I found myself bathed in perspiration. Despite the open door and windows, not a breath of air stirred in the place, but the room was laden with the oppressive perfume of those night-scented flowers which I have mentioned elsewhere, for it was faintly perceptible to me, despite the wet silk. Once, a bat flew half in at one of the windows, striking its wings upon the glass, but almost immediately it flew out again. A big moth fluttered around the room, persistently banging its wings against the lamp-shade. But nothing else within or without the house stirred, if I except the occasional restless movements of the Major. Then all at once--and not gradually as I had anticipated--the meter at my feet began to register. Instantly, I looked to the thermometer. It had begun to fall. I glanced across at Major Dale. He was staring at something which seemed to have attracted his attention in a distant corner of the room. Glancing away from the meter, the indicator of which was still moving upward, I looked in the same direction. There was much shadow there, but nevertheless I could not doubt that a very faint vapour was forming in that corner ... rising--rising--rising--slowly higher and higher. It proceeded from some part of the floor concealed by the big saddle-bag chair--the Major's favourite dozing-place (probably from a faulty floor-board), and it was rising visibly, inch upon inch, as I watched, until it touched the ceiling above. Then, like a column of smoke, it spread out, mushroom fashion; it crept in ghostly coils along the cornices, spreading, a dim grey haze, until it obscured a great part of the ceiling. Again I looked across at the Major. He was staring at the phenomenon with eyes which were glassy with amazement. I could see that momentarily he expected the vapour to take shape, to form into some ghoulish thing with a contorted face and clutching, outstretched fingers. But this did not happen. The vapour, which was growing more fine and imperceptible, began to disperse. I glanced from corner to corner of the room, then down to the meter on the floor. The indicator was falling again. Still I made no move, although I could hear Major Dale fidgeting nervously, but I looked across at him ... and a dreadful change had come over his face. He was sitting upright upon the couch, the edge of which he clutched with one hand, whilst with the other he combed the air in a gesture evidently meant to attract my attention. He was trying to speak, but only a guttural sound issued from his throat. His staring eyes were set in a glare of stark horror upon the door of the study.