I was sitting with some book or other in front of me, not really reading. With every nerve on edge, I was waiting and watching for this being I could feel near me. I knew it was there somewhere. But where? What was it doing? How could I get hold of it? Opposite was my bed, an old oak four-poster. To my right was the fireplace. On the left the door, which I had made sure was locked. Behind me was a very large, mirrored wardrobe before which I shaved and dressed every day. Whenever I passed it I could see myself full length. So there I was, pretending to this presence which I knew was spying on me that I was reading. All of a sudden I felt it reading over my shoulder, brushing against my ear. Leaping to my feet, I turned round so quickly that I nearly fell over. Believe it or not, though the room was bright as day, there was no sign of me in the mirror. It was empty, clear and full of light. But my reflection was not in it, despite the fact that I was standing directly in front of it. I looked at the large glass, clear now from top to bottom. I looked at it in terror. I dared not take a step forward, knowing that this being was in between. I knew that although it would slip away from me again, its own invisible body had absorbed my own reflection. I was so frightened! Then suddenly I saw myself begin to appear from the misty depths of the mirror, rising as if from a body of water. The water itself seemed to shift slowly from left to right revealing, second by second, an increasingly sharper reflection of myself. It was like the end of an eclipse. What was concealing me looked like an opaqueness gradually turning transparent. Finally I could see myself clearly again, as I do when I look in the mirror every day. But now I had seen it. The terror of that moment remains with me and makes me tremble still. The following day I came here and asked to be admitted.

And now, gentlemen, I come to the end of my story. Having been fairly sceptical for some time, Dr Marrande decided to make a little unaccompanied trip to my part of the world. It transpires that three of my neighbours are now in a similar condition to the one I have described, isn’t that so?’

‘Absolutely true!’ the doctor replied.

‘You instructed them to leave out some milk or water in the bedroom every night to see if these liquids disappeared or not. They did. They disappeared just as they did in my house, didn’t they?’

With great seriousness the doctor replied, ‘They did indeed.’