I was only five feet away and directly in what should have been his line of vision.

It was uncanny.

I felt myself a ghost, what of my invisibility.

I waved my hand back and forth, of course without effect; but when the moving shadow fell across his face I saw at once that he was susceptible to the impression.

His face became more expectant and tense as he tried to analyze and identify the impression.
He knew that he had responded to something from without, that his sensibility had been touched by a changing something in his environment; but what it was he could not discover.