that
I desired to accomplish my purpose. He knew that I would do what I
said--that his own fate was involved in mine. For that reason, and for
no other, he shielded me. He thrust me into that dark hiding-place--a
relic of old days, known only to himself. He took his meals in his own
room, and so was able to give me part of his food. It was agreed that
when the police left the house I should slip away by night and come back
no more. But in some way you have read our plans." She tore from the
bosom of her dress a small packet. "These are my last words," said she;
"here is the packet which will save Alexis. I confide it to your honour
and to your love of justice. Take it! You will deliver it at the Russian
Embassy. Now, I have done my duty, and----"

"Stop her!" cried Holmes. He had bounded across the room and had
wrenched a small phial from her hand.

"Too late!" she said, sinking back on the bed. "Too late! I took the
poison before I left my hiding-place. My head swims! I am going! I
charge you, sir, to remember the packet."

"A simple case, and yet, in some ways, an instructive one," Holmes
remarked, as we travelled back to town. "It hinged from the outset upon
the pince-nez. But for the fortunate chance of the dying man having
seized these, I am not sure that we could ever have reached our
solution. It was clear to me, from the strength of the glasses, that
the wearer must have been very blind and helpless when deprived of them.
When you asked me to believe that she walked along a narrow strip of
grass without once making a false step, I remarked, as you may remember,
that it was a noteworthy performance. In my mind I set it down as an
impossible performance, save in the unlikely case that she had a second
pair of glasses. I was forced, therefore, to consider seriously the
hypothesis that she had remained within the house. On perceiving the
similarity of the two corridors, it became clear that she might very
easily have made such a mistake, and, in that case, it was evident that
she must have entered the professor's room. I was keenly on the alert,
therefore, for whatever would bear out this supposition, and I examined
the room narrowly for anything in the shape of a hiding-place. The
carpet seemed continuous and firmly nailed, so I dismissed the idea of
a trap-door. There might well be a recess behind the books. As you are
aware, such devices are common in old libraries. I observed that books
were piled on the flo