It was not until Mr. Henley had made another and longer visit to the
dark room that he became convinced beyond all doubt that the work of
sealing up the place had been done from within, and that there was,
and had been, no other outlet but that through which he had entered.
To suppose that the main wall of the house had been closed in at a
later period would be preposterous, and for manifest reasons. His
examination of the room's interior had been most thorough and
exhaustive. The place was smoothly plastered upon the inside, and
even the mason's trowel had been found upon the floor within, so that
it became at once evident that those who had done the work had been
self-immured. Although the reason for such an act was utterly beyond
his comprehension, Paul felt a certain satisfaction in having reached
this conclusion, as it showed the impossibility of Dorothy's being in
any way implicated in the affair. It seemed even possible that she
was ignorant of it. But this discovery in no wise lessened the
mystery; it rather increased it.

A few evenings after Paul's decision regarding the self-immurement of
those discovered in the vault, he and Ah Ben were again enjoying
their pipes by the great fireplace in the hall. The elder man was
generally disposed to conversation at this hour; and after Dorothy
had retired, Paul alluded to the strange scene he had witnessed
through the chimney, and expressed a desire to learn something of
occultism. Taking his long-stemmed pipe from his lips, the old man
gazed earnestly into the fire. He seemed to be thinking of what to
say, and to be drawing inspiration from the glowing embers and
dancing flames before him. At last he spoke:

"Occultism, Mr. Henley, is difficult--nay, almost impossible--to
explain to a layman; or if explained, remains incomprehensible; and