I turned my eye again toward the window, and perceived that the light was still there; but the change which I had noticed was occasioned by a change in the position of the lamp or candle within.

Hence, that some person was there was an unavoidable inference.
I paused to deliberate on the propriety of advancing.

Might I not advance cautiously, and, therefore, without danger?
Might I not knock at the door, or call, and be apprized of the nature of my visitant before I entered?
I approached and listened at the door, but could hear nothing.
I knocked at first timidly, but afterwards with loudness.

My signals were unnoticed.

I stepped back and looked, but the light was no longer discernible.