All at once I sat up.  I had become lost in an absorbing reverie.  The Egyptian smell had seemed to get on my nerves—­on my memory—­on my very will.

At that moment I had a thought which was like an inspiration.  If I was influenced in such a manner by the smell, might it not be that the sick man, who lived half his life or more in the atmosphere, had gradually and by slow but sure process taken into his system something which had permeated him to such degree that it had a new power derived from quantity—­or strength—­or . . .

I was becoming lost again in a reverie.  This would not do.  I must take such precaution that I could remain awake, or free from such entrancing thought.  I had had but half a night’s sleep last night; and this night I must remain awake.  Without stating my intention, for I feared that I might add to the trouble and uneasiness of Miss Trelawny, I went downstairs and out of the house.  I soon found a chemist’s shop, and came away with a respirator.  When I got back, it was ten o’clock; the Doctor was going for the night.  The Nurse came with him to the door of the sick-room, taking her last instructions.  Miss Trelawny sat still beside the bed.  Sergeant Daw, who had entered as the Doctor went out, was some little distance off.

When Nurse Kennedy joined us, we arranged that she should sit up till two o’clock, when Miss Trelawny would relieve her.  Thus, in accordance with Mr. Trelawny’s instructions, there would always be a man and a woman in the room; and each one of us would overlap, so that at no time would a new set of watchers come on duty without some one to tell of what—­if anything—­had occurred.  I lay down on a sofa in my own room, having arranged that one of the servants should call me a little before twelve.  In a few moments I was asleep.

When I was waked, it took me several seconds to get back my thoughts so as to recognise my own identity and surroundings.  The short sleep had, however, done me good, and I could look on things around me in a more practical light than I had been able to do earlier in the evening.  I bathed my face, and thus refreshed went into the sick-room.  I moved very softly.  The Nurse was sitting by the bed, quiet and alert; the Detective sat in an arm-chair across the room in deep shadow.  He did not move when I crossed, until I got close to him, when he said in a dull whisper: 

“It is all right; I have not been asleep!” An unnecessary thing to say, I thought—­it always is, unless it be untrue in spirit.  When I told him that his watch was over; that he might go to bed till I should call him at six o’clock, he seemed relieved and went with alacrity.  At the door he turned and, coming back to me, said in a whisper: 

“I sleep lightly and I shall have my pistols with me.  I won’t feel so heavy-headed when I get out of this mummy smell.”

He too, then, had shared my experience of drowsiness!