rom," I said, as Gatton and
I walked through the cottage to meet the new arrivals.

"We know more than that," he retorted. "We know how _Sir Marcus_
died!"

"Gatton!" I cried excitedly, as we approached a group waiting in the
porch--"do you mean--"

He looked at me grimly.

"I mean," he said slowly, "that I have not forgotten the _gas-plug_ in
the wall of that recess in the supper-room at the Red House! The only
thing I was doubtful about (the means by which the victim was induced
to admit the gas into the room) is now as clear as daylight."

"You are right, Gatton," I agreed. "The same trick has succeeded
twice."

"The same trick, as you say, Mr. Addison; with one trifling variation,
a device which would only suggest itself to such a brain as that of--"

"Dr. Damar Greefe!" I cried.

"I believe you are right."

And now fell an awesome silence; for whilst Gatton and I stood
bare-headed, the unfortunate Eric Coverly was being carried out to the
waiting car; and even as I turned my eyes away in horror from that
spectacle, I was endeavoring to frame the words in which I should
acquaint Isobel with this second ghastly tragedy.

Here, indeed, was a new development of "the _Oritoga_ mystery"; and so
queerly does the mind depart from the actualities at such a moment
that I found myself thinking, even whilst Gatton was talking to me, of
the bold head-lines which would greet readers of the press in the
morning--and of the renewed excitement which would sweep throughout
the length and breadth of the land when this dreadful alibi was
proven.

Over the details of that gruesome tragedy I feel myself compelled to
pass lightly, for even now the horror of it remains with me. The fumes
of the poisonous gray mist lingered for hours in the house; and there
were official visitations, testimonies and attestations, and the
hundred and one formalities which invariably accompany such a tragedy
but which I need not deal with in detail here.

Coates returned with the Rover, just as the body of the victim was
being removed, and his account of what had occurred was simple enough,
and followed the lines which we had anticipated. He had locked up and
then gone to the garage for the car as I had directed him to do,
returning to the cottage in time to admit Eric Coverly, whom he showed
into the study, having informed him that I should be back in less than
ten minutes. He had then proceeded to Denmark Hill railway station
only to find,