'But instinct has a basis in reason.'

'Has it? I am not enough of a psychologist to answer that question.
Tell me why you are asking me all this.'

'Because I am afraid to tell you what is in my mind. Do you remember
what Merril said?'

'Yes,' I replied; 'he said that according to symptoms my friend had been
poisoned. But he didn't see how it could possibly be, and he said that
the case was completely beyond him.'

'Exactly. When I went into that room, I of course had your words in my
mind. India has a hundred poisons unknown to the West, many of them are
subtle, almost undiscoverable. I called to my mind what I had learned in
India, what I had seen and done there. Frankly, I don't understand your
friend's case. Had it been in India, I should have understood it, and
what was possible, ay, what would have amounted to certainty there, was
utterly impossible in England--at least, so it seemed to me. But I acted
on the assumption that I was in India.'

'You mean that you injected an antidote for a poison that you know of?' I
ventured.

He looked at me steadily for a few seconds, but he did not speak.

'Now look here, Luscombe,' he said, after a long silence, 'I hesitated to
tell you this, because it is a serious business.'

I nodded.

'You see,' he went on, 'we are not in the realm of proof. But as sure as
I am a living man, if your friend was poisoned, some one poisoned him,
unless he had a curious way of trying to commit suicide.'

'He didn't try to commit suicide,' I replied.

'You remember that mark in the arm?'

I nodded.

'In another hour it will be gone. If he had died, it would not be there.
I was a blind fool not to have seen it. I examined his arm just before
we came in here,--the discolourment has nearly passed away. In an hour
there'll be only a little spot about the size of a pin-prick. Do you
feel free to tell me anything of your suspicions? Remember, they can
only be suspicions. There can be no possible proof of anything, and even
although you may have drawn conclusions, which to you are unanswerable,
you might be committing the cruellest crime against another man by
speaking them aloud.'

'Then I'll not tell you my suspicions,' I said. 'I will only recount
certain incidents.'

Then I told him the things I remembered.

Colonel McClure looked very grave.

'No,' he said, at length, 'this is something which we dare not speak of
aloud. I must think this out, my boy, so