"Diamonds, at any rate," replied Hewitt, "whether Samuel's or somebody
else's. But they can't have been there long. How often is this cupboard
opened?"

"Every Saturday reg'lar, sir," replied the housekeeper; "just to dust it
out and see things is right."

"Now, see here!" said Martin Hewitt, "I've had luck in my conjectures as
yet, and I'll try again. Here is what I believe has happened. Every word
that Samuel told me about the theft of those diamonds was true, except
as to their ownership. Denson has planned all along to rob him of as
big a collection of diamonds as he could prompt him to get together,
and he has played up to this for months. His smaller dealings one way
and another were ground-bait. Very artfully he let Samuel take the
diamonds safely away once, in order that he should be less watchful and
less suspicious the second time. This second time he does the trick
exactly as we see. He hangs up the imaginary American's hat, he escapes
by the fanlight, and he goes out by the back way to avoid the
housekeeper's observation. He has arranged beforehand for this, too. He
has seized an opportunity when the housekeeper has been out of his box
to get wax impressions of these two keys, and he has made copies of
them. And here we come on a curious thing. It is easy enough to
understand why he should foresee and get himself a key for the back
door, in order to make his escape. But why the key of the hose-cupboard?
Why, indeed, should he leave the diamonds behind him at all? It is plain
that he meant to come back for them--probably at night. He would have
been wholly free from observation in that quiet courtyard, and he could
let himself in, get the diamonds, and leave again without exciting the
smallest alarm or suspicion. But why take all the trouble? Why not stick
to the plunder from the beginning? The plain inference is that he
feared somebody or something. He feared being stopped and searched, or
he feared being waylaid _sometime during yesterday_. By whom? There's
the puzzle, and I can't see the bottom of it, I confess. If I could,
perhaps I might know something of last night's murder.

"As to Samuel's prevarications, there is only one explanation that will
fit, now that the rest is made clear. He must have been entrusted with
these diamonds by a private owner, for sale--secretly. Some lady of
conspicuous position in difficulties, probably--perhaps unknown to her
husband. Such things occur every day. A common ex