his fingers were trained to such work--he was prepared
to swear that the surface of the Chinese paper covering the wall was
perfectly continuous. He drummed upon it lightly with his finger-tips,
here and there over the surface above the bed. And in this fashion he
became enlightened.

A portion, roughly a foot in height and two feet long, yielded a
slightly different note to his drumming; whereby he knew that that part
of the paper was not ATTACHED to the wall. He perceived the truth. The
trap, when closed, fitted flush with the back of the wall-paper, and
this paper (although when pasted upon the walls it showed no evidence of
the fact) must be TRANSPARENT.

From some dark place beyond, it was possible to peer in THROUGH the
rectangular patch of paper as through a window, at the occupant of the
bunk below, upon whom the shaded lamp directly poured its rays!

He examined more closely a lower part of the wall, which did not fall
within the shadow of the purple lamp-shade; for he was thinking of the
draught which had followed the opening of the trap. By this examination
he learnt two things: The explanation of the draught, and that of a
peculiar property possessed by the mural decorations. These (as Soames
had observed before him) assumed a new form if one stared at them
closely; other figures, figures human and animal, seemed to take
shape and to peer out from BEHIND the more obvious designs which were
perceptible at a glance. The longer and the closer one studied these
singular walls, the more evident the UNDER design became, until it
usurped the field of vision entirely. It was a bewildering delusion; but
M. Max had solved the mystery.

There were TWO designs; the first, an intricate Chinese pattern,
was painted or printed upon material like the finest gauze. This
was attached over a second and vividly colored pattern upon thick
parchment-like paper--as he learnt by the application of the point of
his pocket-knife.

The observation trap was covered with this paper, and fitted so nicely
in the opening that his fingers had failed to detect, through the
superimposed gauze, the slightest irregularity there. But, the trap
opened, a perfectly clear view of the room could be obtained through the
gauze, which, by reason of its texture, also admitted a current of air.

This matter settled, M. Max proceeded carefully to examine the entire
room foot by foot. Opening the door in one corner, he entered the
bathroom, in which