What can it mean? Surely my whole chain of reasoning cannot
have been false. It is impossible! And yet this wretched
dog is none the worse. Ah, I have it! I have it!" With a
perfect shriek of delight he rushed to the box, cut the other
pill in two, dissolved it, added milk, and presented it to
the terrier. The unfortunate creature's tongue seemed hardly
to have been moistened in it before it gave a convulsive
shiver in every limb, and lay as rigid and lifeless as if it
had been struck by lightning.

Sherlock Holmes drew a long breath, and wiped the
perspiration from his forehead. "I should have more faith,"
he said; "I ought to know by this time that when a fact
appears to be opposed to a long train of deductions,
it invariably proves to be capable of bearing some other
interpretation. Of the two pills in that box one was of the
most deadly poison, and the other was entirely harmless.
I ought to have known that before ever I saw the box at all."

This last statement appeared to me to be so startling,
that I could hardly believe that he was in his sober senses.
There was the dead dog, however, to prove that his conjecture
had been correct. It seemed to me that the mists in my own
mind were gradually clearing away, and I began to have a dim,
vague perception of the truth.

"All this seems strange to you," continued Holmes,
"because you failed at the beginning of the inquiry to grasp
the importance of the single real clue which was presented
to you. I had the good fortune to seize upon that, and