“So, for awhile we remained locked in a deadly embrace, swaying to and fro, and each straining for the momentary advantage that would have brought the affair to a finish.  The end came unexpectedly.

“One of us tripped on the edge of the mat and we both came down with a crash, he underneath and face downwards.  As we fell, he uttered a sharp cry and began to struggle in a curious, convulsive fashion; but after a time he grew quieter and at last lay quite still and silent.

“At first I took this for a ruse to put me off my guard, and held on more firmly than ever; but presently a characteristic limpness of his limbs suggested a new idea.  Gradually and cautiously I relaxed my hold, and, as he still did not move, I felt about on the mat for the lamp; and when I had found it and pushed over the switch I threw its light on him.

“He was perfectly motionless and did not appear to be breathing.  I turned him over and then saw that it was as I had suspected.  He had held the knife ready for a second blow when I had pinioned him.  He was still grasping it so when we fell, and the point had entered his own chest near the middle line, between the fourth and fifth ribs, and had been driven in up to the very haft by the force of the fall.  He must have died almost instantaneously.

“I stood up and listened.  The place was as silent as the grave; a remarkably apt comparison, by the way.  The pistol shots had apparently not been heard by the police, so there was no fear of interruption from that quarter; and as for the maids they were very carefully keeping out of harm’s way.

“Still, there was a good deal to do, and not so very much time to do it in.  It was now getting on for three o’clock and the sun would be up by four.  Daylight would bring the maids down and everything must be clear before they made their appearance.

“I wasted no time.  One by one, I conveyed the bodies to the laboratory and deposited them in the tank, the accommodation of which was barely equal to the occasion.  The sudden death of the first man had rather puzzled me, but when I lifted him the explanation was obvious enough.  The heavy blow, catching the head obliquely, had dislocated the neck.  So the concussor was not such a very harmless implement after all.

“The slight traces left in transporting the material to the laboratory, I obliterated with great care, excepting the last man’s knife, which I left on the mat.  Then I changed my pajamas, putting the blood-stained suit to soak in the laboratory, strapped up my wound, put on a dressing-gown, opened the street door and shut it rather noisily and ascended with a candle to the upper floor.

“The housemaid’s bedroom door was open and the room empty.  I tapped at the cook’s door and elicited a faint scream.

“‘Who’s that?’ a shaky voice demanded.

“‘It is I,’ was my answer—­a stupid answer, by the way, but, of course, they knew my voice.  The door opened and the two women appeared, fully dressed but rather disheveled and both very pale.