I heard a gentle sound of movement, and then all was silent once more, though the smell grew stronger.

For half an hour I sat with straining ears.
Then suddenly another sound became audible--a very gentle, soothing sound, like that of a small jet of steam escaping continually from a kettle.

The instant that we heard it, Holmes sprang from the bed, struck a match, and lashed furiously with his cane at the bell-pull.
"You see it, Watson ?" he yelled.

"You see it ?" But I saw nothing.

At the moment when Holmes struck the light I heard a low, clear whistle, but the sudden glare flashing into my weary eyes made it impossible for me to tell what it was at which my friend lashed so savagely.