It was well after one o’clock in the morning when Dr. Silence turned the lamp out and lighted the candle preparatory to going up to bed.  Then Smoke suddenly woke with a loud sharp purr and sat up.  It neither stretched, washed nor turned:  it listened.  And the doctor, watching it, realised that a certain indefinable change had come about that very moment in the room.  A swift readjustment of the forces within the four walls had taken place—­a new disposition of their personal equations.  The balance was destroyed, the former harmony gone.  Smoke, most sensitive of barometers, had been the first to feel it, but the dog was not slow to follow suit, for on looking down he noted that Flame was no longer asleep.  He was lying with eyes wide open, and that same instant he sat up on his great haunches and began to growl.

Dr. Silence was in the act of taking the matches to re-light the lamp when an audible movement in the room behind him made him pause.  Smoke leaped down from his knee and moved forward a few paces across the carpet.  Then it stopped and stared fixedly; and the doctor stood up on the rug to watch.

As he rose the sound was repeated, and he discovered that it was not in the room as he first thought, but outside, and that it came from more directions than one.  There was a rushing, sweeping noise against the window-panes, and simultaneously a sound of something brushing against the door—­out in the hall.  Smoke advanced sedately across the carpet, twitching his tail, and sat down within a foot of the door.  The influence that had destroyed the harmonious conditions of the room had apparently moved in advance of its cause.  Clearly, something was about to happen.

For the first time that night John Silence hesitated; the thought of that dark narrow hall-way, choked with fog, and destitute of human comfort, was unpleasant.  He became aware of a faint creeping of his flesh.  He knew, of course, that the actual opening of the door was not necessary to the invasion of the room that was about to take place, since neither doors nor windows, nor any other solid barriers could interpose an obstacle to what was seeking entrance.  Yet the opening of the door would be significant and symbolic, and he distinctly shrank from it.

But for a moment only.  Smoke, turning with a show of impatience, recalled him to his purpose, and he moved past the sitting, watching creature, and deliberately opened the door to its full width.

What subsequently happened, happened in the feeble and flickering light of the solitary candle on the mantlepiece.

Through the opened door he saw the hall, dimly lit and thick with fog.  Nothing, of course, was visible—­nothing but the hat-stand, the African spears in dark lines upon the wall and the high-backed wooden chair standing grotesquely underneath on the oilcloth floor.  For one instant the fog seemed to move and thicken oddly; but he set that down to the score of the imagination.  The door had opened upon nothing.