It must have been about two o’clock in the morning when I was woken abruptly by a loud banging noise. It was such a bitterly cold night that I did not fancy the idea of getting up, so I sat in bed listened. Since I heard nothing more, I concluded that the sound must have come from the street. I was just going back to sleep when there was another loud bang. The sound was so extraordinary that this time I jumped out of bed at once. I put on my dressing-gown and tiptoed downstairs. Feeling my way carefully, I found the drawing-room door open and could not remember if I had left it like that. I quickly turned on the lights but could see nothing unusual. I felt rather ashamed of my foolish behavior and began climbing the stairs when I heard the same noise again. It came distinctively from above. I dashed upstairs and went into all the bedrooms one after another, but there was nothing that could possibly have made such a sound. I went across to one of the windows. It was so cold outside that ice had formed on the window-panes. I scraped it away and looked down on the garden below. Lamps from the street in the distance provided sufficient light to see by. It was snowing heavily and the branches of the bare trees looked like white arms against the night sky. There was certainly no sign that anyone had been walking in the garden, for it would have been easy to make out footprints. As I was beginning to feel cold, I went to my room, only then did I understand: the water in the pipes leading to the tank in the attic was beginning to freeze and the pipes were protesting loudly!