Singular though my friend's proceedings appeared to me, I had ceased
to wonder at anything. Since Nayland Smith's arrival at my rooms I
seemed to have been moving through the fitful phases of a nightmare.
My friend's account of how he came by the wound in his arm;
the scene on our arrival at the house of Sir Crichton Davey;
the secretary's story of the dying man's cry, "The red hand!";
the hidden perils of the study; the wail in the lane--
all were fitter incidents of delirium than of sane reality.
So, when a white-faced butler made us known to a nervous old lady
who proved to be the housekeeper of the next-door residence,
I was not surprised at Smith's saying:

"Lounge up and down outside, Petrie. Everyone has cleared off now.
It is getting late. Keep your eyes open and be on your guard.
I thought I had the start, but he is here before me, and, what is worse,
he probably knows by now that I am here, too."

With which he entered the house and left me out in the square,
with leisure to think, to try to understand.

The crowd which usually haunts the scene of a sensational crime
had been cleared away, and it had been circulated that Sir Crichton
had died from natural causes. The intense heat having driven most
of the residents out of town, practically I had the square to myself,
and I gave myself up to a brief consideration of the mystery in which I
so suddenly had found myself involved.

By what agency had Sir Crichton met his death?
Did Nayland Smith know? I rather suspected that he did.
What was the hidden significance of the perfumed envelope?