of supernatural visitations, only exposed after great
difficulty by professional research. Along such lines, therefore, this
man was prepared to operate, and he believed it might be possible that a
maniac, in possession of some physical secret, would be found among
the inhabitants of the manor house. He did not, however, elaborate this
opinion, but kept it to himself. Indeed, the human element of jealousy,
so often responsible for the frustration of the worthiest human
ambitions, was not absent from the minds of the four now concerned with
this problem.

Each desired to solve it, and while no rivalry existed among them, save
in the case of the two older men, it was certain that the eldest of
the four would not lose his hold on his own theory, or be at very vital
pains to stultify it. All, however, were fully conscious of the danger
before them, and Frith, from the first, directed that none was to work
alone, either in the Grey Room or elsewhere.

At noon a telegram arrived for Mr. Frith from Scotland Yard. It recorded
the fact that Peter Hardcastle was dead, and that examination had
revealed no cause for his end. The news reached Sir Walter at once, and
if ever he rejoiced in the death of a fellow-creature, it was upon this
occasion. It meant unspeakable relief both for him and his daughter.

The detectives began their operations after a midday meal, and having
first carefully studied the Grey Room in every visible particular, they
emptied it of its contents, and placed the pictures, furniture, and
statuette outside in the corridor. They asked for no assistance, and
desired that none should visit the scene of their labors. The apartment,
empty to the walls, they examined minutely; with the help of ladders,
they investigated the outer walls on the east and south side; and they
probed the chimney from above and below. They searched the adjoining
room--Mary's old nursery--to satisfy themselves that no communication
existed, and they drove an iron rod through the walls in various
directions, only to prove they were of solid stone, eighteen inches
thick within and two feet thick without. There was no apartment on the
other side of the chamber. It completed the eastern angle of the house
front, and behind it, inside, the corridor terminated at an eastern
window parallel with the Grey Room oriel, but flat and undecorated--a
modern window inserted by Sir Walter's grandfather to lighten a dark
corner. Not a foot of the walls t