himself hampered from the fact that my room was so close to his, and
from a suspicion that I would be on the watch that night. Naturally,
he could not for a moment believe that I suspected him! But I might
see him leaving his room when he was about to go to Mademoiselle
Stangerson. He waited till I was asleep, and my friend Sainclair
was busy trying to rouse me. Ten minutes after that Mademoiselle
was calling out, "Murder!"

"How did you come to suspect Larsan?" asked the President.

"My pure reason pointed to him. That was why I watched him. But
I did not foresee the drugging. He is very cunning. Yes, my pure
reason pointed to him; but I required tangible proof so that my
eyes could see him as my pure reason saw him."

"What do you mean by your pure reason?"

"That power of one's mind which admits of no disturbing elements
to a conclusion. The day following the incident of 'the
inexplicable gallery,' I felt myself losing control of it. I had
allowed myself to be diverted by fallacious evidence; but I
recovered and again took hold of the right end. I satisfied myself
that the murderer could not have left the gallery, either naturally
or supernaturally. I narrowed the field of consideration to that
small circle, so to speak. The murderer could not be outside that
circle. Now who was in it? There was, first, the murderer. Then
there were Daddy Jacques, Monsieur Stangerson, Frederic Larsan, and
myself. Five persons in all, counting in the murderer. And yet,
in the gallery, there were but four. Now since it had been
demonstrated to me that the fifth could not have escaped, it was