st. How was it possible for such a rock to be thus
dislodged? By an earthquake? But nothing of the kind had occurred. He
was a light sleeper, and was easily aroused by anything unusual.
Could the castle have "settled?" Impossible. It was too old. It had
long since shaken down into its deep bed. Still, old buildings do
often settle, and in fault of any better explanation he was compelled
to adopt something like this.

In any event, there seemed very great danger that the package had
been lost. Again and again he thrust his arm far in, but found only
vacancy. Then he put his hand downward as far as he could. It touched
something which felt like a stone pavement.

This pavement was about eight inches lower than the one upon which he
was. All this made the matter still more incomprehensible.

But Harry had come forth to seek after this very thing, namely, some
mysterious opening into a side-passage, and after the first surprise
it occurred to him that this might be what he wished to find. And now
the fact of the stone jutting forth became intelligible, though this
new explanation promised ill for the safety of the package. It was
evident that this stone was movable, and afforded in some way an
entrance to this passage. It seemed strange that so vast a stone
should be movable, yet there was the fact. Perhaps also it was less
massive than it seemed. Perhaps it was a mere slab and opened like a
door. But how?

He now examined its surface with the most careful and minute
scrutiny. In vain. Over all the surface and over all the edges there
was nothing that indicated any means by which such a stone could be
moved--nothing of the nature of hinges, and nothing of the nature of
a handle, by which to grasp it so as to move it. Yet it was movable,
and had been moved lately. Perhaps it could be moved without any help
from a handle.

He now thrust his arm through, and, grasping it, pulled at it with
all his strength. His utmost effort, however, made no impression. He
found that the stone was massive within as without, that it was no
thin slab, but one which his arm could not surround--at least
eighteen inches in solid thickness where his arm held it. Yet the
stone did move, and had been moved. The matter became now more
incomprehensible than ever. It could be moved. It had been moved, yet
there was a secret contrivance here into which he could not
penetrate.

Again the thought came to him of the package which contained Katie's