But the cat, too, had heard that dreadful bark; and it, too, had understood.  This was more than it had bargained for.  Across the dim shadows of that haunted room there must have passed some secret signal of distress between the animals.  Smoke stood up and looked swiftly about him.  He uttered a piteous meow and trotted smartly away into the greater darkness by the windows.  What his object was only those endowed with the spirit-like intelligence of cats might know.  But, at any rate, he had at last ranged himself on the side of his friend.  And the little beast meant business.

At the same moment the collie managed to gain the door.  The doctor saw him rush through into the hall like a flash of yellow light.  He shot across the oilcloth, and tore up the stairs, but in another second he appeared again, flying down the steps and landing at the bottom in a tumbling heap, whining, cringing, terrified.  The doctor saw him slink back into the room again and crawl round by the wall towards the cat.  Was, then, even the staircase occupied?  Did They stand also in the hall?  Was the whole house crowded from floor to ceiling?

The thought came to add to the keen distress he felt at the sight of the collie’s discomfiture.  And, indeed, his own personal distress had increased in a marked degree during the past minutes, and continued to increase steadily to the climax.  He recognised that the drain on his own vitality grew steadily, and that the attack was now directed against himself even more than against the defeated dog, and the too much deceived cat.

It all seemed so rapid and uncalculated after that—­the events that took place in this little modern room at the top of Putney Hill between midnight and sunrise—­that Dr. Silence was hardly able to follow and remember it all.  It came about with such uncanny swiftness and terror; the light was so uncertain; the movements of the black cat so difficult to follow on the dark carpet, and the doctor himself so weary and taken by surprise—­that he found it almost impossible to observe accurately, or to recall afterwards precisely what it was he had seen or in what order the incidents had taken place.  He never could understand what defect of vision on his part made it seem as though the cat had duplicated itself at first, and then increased indefinitely, so that there were at least a dozen of them darting silently about the floor, leaping softly on to chairs and tables, passing like shadows from the open door to the end of the room, all black as sin, with brilliant green eyes flashing fire in all directions.  It was like the reflections from a score of mirrors placed round the walls at different angles.  Nor could he make out at the time why the size of the room seemed to have altered, grown much larger, and why it extended away behind him where ordinarily the wall should have been.  The snarling of the enraged and terrified collie sounded sometimes so far away; the ceiling seemed to have raised itself so much higher than before, and much of the furniture had changed in appearance and shifted marvellously.