en catch--for
all the others were fastened inside. Out of that window, then, he went."

"But how? The window is fifty feet up."

"Of course it is. But why _will_ you persist in assuming that the only way
of escape by a window is downward? See, now, look up there. The window is
at the top floor, and it has a very broad sill. Over the window is nothing
but the flat face of the gable-end; but to the right, and a foot or two
above the level of the top of the window, an iron gutter ends. Observe, it
is not of lead composition, but a strong iron gutter, supported, just at
its end, by an iron bracket. If a tall man stood on the end of the
window-sill, steadying himself by the left hand and leaning to the right,
he could just touch the end of this gutter with his right hand. The full
stretch, toe to finger, is seven feet three inches. I have measured it. An
active gymnast, or a sailor, could catch the gutter with a slight spring,
and by it draw himself upon the roof. You will say he would have to be
_very_ active, dexterous, and cool. So he would. And that very fact helps
us, because it narrows the field of inquiry. We know the sort of man to
look for. Because, being certain (as I am) that the man was in the room, I
_know_ that he left in the way I am telling you. He must have left in some
way, and, all the other ways being impossible, this alone remains,
difficult as the feat may seem. The fact of his shutting the window behind
him further proves his coolness and address at so great a height from the
ground."

All this was very plain, but the main point was still dark.

"You say you _know_ that another man was in the room," I said; "how do you
know that?"

"As I said, by an obvious inference. Come, now, you shall guess how I
arrived at that inference. You often speak of your interest in my work,
and the attention with which you follow it. This shall be a simple
exercise for you. You saw everything in the room as plainly as I myself.
Bring the scene back to your memory, and think over the various small
objects littering about, and how they would affect the case. Quick
observation is the first essential for my work. Did you see a newspaper,
for instance?"

"Yes. There was an evening paper on the floor, but I didn't examine it."

"Anything else?"

"On the table there was a whisky decanter, taken from the tantalus-stand
on the sideboard, and one glass. That, by the by," I added, "looked as
though only one person were pres