invisible ruffian seemed quite
trivial and inconsequent; and yet they framed his death warrant. I did
not myself realize it fully at the moment. As I closed the slide and
stepped back, I was conscious only that a useful train of thought had
been started. 'Put some more coke in the stove and let us go to sleep.'
Yes; there was a clear connection between the idea of 'stove' and that
of 'sleep,' a sleep of infinite duration. Therein lay the solution of
the problem.

"I walked slowly down the stairs tracing the connection between the
ideas of 'stove' and 'sleep.' The nauseous air that had filtered through
from that room spoke eloquently of sealed windows and stopped crevices.
It was a frosty night and the murderers were chilly. A back-draught in
the stovepipe would fill the room with poisonous gases and probably
suffocate these wretches slowly and quietly. But how was it to be
brought about? For a moment I thought of climbing to the roof and
stopping the chimney from above. But the plan was a bad one. The police
might see me and make some regrettable mistake with a revolver. Besides
it would probably fail. The stoppage of the draught would extinguish the
fire and the pungent coke-fumes would warn the villains of their danger.
Still closely pursuing the train of thought, I stepped into my bedroom
and lit the gas; I turned to glance round the room; and, behold! the
problem was solved.

"In the fireplace stood a little brass stove of Russian make; a tiny
affair, too small to burn anything but charcoal; but, as charcoal was
easily obtainable in East London, I had bought it and fixed it myself.
It was perfectly safe in a well-ventilated room, though otherwise very
dangerous; for the fumes of charcoal, consisting of nearly pure carbon
dioxide, being practically inodorous, give no warning.

"My course was now quite clear. The stove was fitted with
asbestos-covered handles; a box of charcoal stood by the hearth, and in
the corner was an extra length of stovepipe for which I had had no use.
But I had a use for it now.

"I lit the charcoal in the stove, and, while it was burning up, carried
the stovepipe and the box of fuel upstairs. Then I returned for the
stove, inside which the charcoal was now beginning to glow brightly. I
fixed on the extra length of pipe and, with my hand, felt the stream of
hot air--or rather hot carbon dioxide gas--pouring out of its mouth. I
tried the pipe against the opening and found that it would rest