Next came a close examination of the ceiling and side walls, the
floor, the hangings, the pictures, the rugs, everything. Kennedy
was tapping here and there all over the wall, as if to discover
whether there was any such hollow sound as a cavity might make.
There was none.

A low exclamation from him attracted my attention, though it
escaped Brixton. His tapping had raised the dust from the velvety
wall-paper wherever he had tried it. Hastily, from a corner where
it would not be noticed, he pulled off a piece of the paper and
stuffed it into his pocket. Then followed a hasty examination of
the intake of the ventilating apparatus.

Apparently satisfied with his examination of things in the den,
Craig now prepared to trace out the course of the telephone and
light wires in the house. Brixton excused himself, asking us to
join him in the library up-stairs after Craig had completed his
investigation.

Nothing was discovered by tracing the lines back, as best we
could, from the den. Kennedy therefore began at the other end, and
having found the points in the huge cellar of the house where the
main trunk and feed wires entered, he began a systematic search in
that direction.

A separate line led, apparently, to the den, and where this line
feeding the Osram lamp passed near a dark storeroom in a corner
Craig examined more closely than ever. Seemingly his search was
rewarded, for he dived into the dark storeroom and commenced