he thought
of that word mystery, as it seemed to come with a dull impact upon his
heart, that heart throbbed and beat still more rapidly, for a strange
influence connected mystery with mystery; and Brace Norton, mad almost
with excitement, followed to where he had heard the sound, felt in the
intense darkness for the window, found it as he had expected--open, and
drawing himself up, he leaned in, and listened, half feeling that it was
but to receive a fierce blow upon the head; but, no: all was still.

"I'll risk all," muttered Brace. "My position as an officer, and my
word of honour that I was impelled by good motives, must be sufficient
to clear me from all blame."

The next minute he was in a small lobby--so he judged it to be--and
feeling gently along the wall, he soon found the open door, and stood in
what seemed to be a long stone passage--the passage, in fact, though he
knew it not, which led from the servants' offices to the grand entrance
of the house.

Should he turn to right or left? All was dark and silent; but that a
robbery was in progress he felt now sure. If, he thought, he could
seize the burglar at his work, there would be some claim again on Sir
Murray Gernon's generosity; but if he tried now to alarm the inmates,
and the burglar took flight, there was nothing but his own word to clear
him from what would look to suspicious eyes like a clandestine entry to
the Castle for reasons of his own.

Brace wavered for a few moments as he stood there listening in the black
darkness; but directly after a strange impulse moved him to proceed; and
cautiously feeling his way along, he stood at length at the foot of the
grand staircase, irresolute as to the next direction he should take.

For a few seconds he could hear nothing but the loud tick of a clock
somewhere close at hand, but directly after came a slight grating, which
he knew to be a key turning in a lock; and gliding in the direction, he
found an open door, through which he passed in time to hear a faint
ejaculation, as some one brushed against a light chair. Then came once
more the sound of key in lock, and Brace suspected that he must be in a
suite of rooms, leading one from the other.

There was furniture all around, but by means of exercising great caution
he was enabled to creep on slowly till his hand rested upon an open
door, against the edge of which he nearly struck his forehead. On
trying to the left, he found that his hand rested on