he could
tell that. And he now knew positively that his patient--the patient who
had alarmed Barker, and had then tripped down the corridor with that
dancing footstep--was somewhere concealed within the four walls
commanded by his spy-hole. He also realised--and this was most
unusual--that this individual whom he desired to watch knew that he was
being watched. And, further, that the stranger himself was also
watching! In fact, that it was he, the doctor, who was being
observed--and by an observer as keen and trained as himself.

An inkling of the true state of the case began to dawn upon him, and he
was on the verge of entering--indeed, his hand already touched the
door-knob--when his eye, still glued to the spy-hole, detected a slight
movement. Directly opposite, between him and the fireplace, something
stirred. He watched very attentively and made certain that he was not
mistaken. An object on the mantelpiece--it was a blue vase--disappeared
from view. It passed out of sight together with the portion of the
marble mantelpiece on which it rested. Next, that part of the fire and
grate and brass fender immediately below it vanished entirely, as though
a slice had been taken clean out of them.

Dr. Silence then understood that something between him and these objects
was slowly coming into being, something that concealed them and
obstructed his vision by inserting itself in the line of sight between
them and himself.

He quietly awaited further results before going in.

First he saw a thin perpendicular line tracing itself from just above
the height of the clock and continuing downwards till it reached the
woolly fire-mat. This line grew wider, broadened, grew solid. It was no
shadow; it was something substantial. It defined itself more and more.
Then suddenly, at the top of the line, and about on a level with the
face of the clock, he saw a round luminous disc gazing steadily at him.
It was a human eye, looking straight into his own, pressed there against
the spy-hole. And it was bright with intelligence. Dr. Silence held his
breath for a moment--and stared back at it.

Then, like some one moving out of deep shadow into light, he saw the
figure of a man come sliding sideways into view, a whitish face
following the eye, and the perpendicular line he had first observed
broadening out and developing into the complete figure of a human being.
It was the patient. He had apparently been standing there in front of
the fir