t was effected."

The guests uttered many exclamations of surprise.

"Certainly, the affair looks serious," said one.

"Well, the police investigated the matter, and, as usual, discovered no
clue whatever."

"They never do, when Arsene Lupin is concerned in it."

"Exactly; and so I decided to ask the assistance of Sherlock Holmes,
who replied that he was ready and anxious to enter the lists with Arsene
Lupin."

"What glory for Arsene Lupin!" said Velmont. "But if our national thief,
as they call him, has no evil designs on your castle, Sherlock Holmes
will have his trip in vain."

"There are other things that will interest him, such as the discovery of
the subterranean passage."

"But you told us that one end of the passage was outside the ramparts
and the other was in this very room!"

"Yes, but in what part of the room? The line which represents the
passage on the charts ends here, with a small circle marked with the
letters `T.G.,' which no doubt stand for `Tour Guillaume.' But the tower
is round, and who can tell the exact spot at which the passage touches
the tower?"

Devanne lighted a second cigar and poured himself a glass of
Benedictine. His guests pressed him with questions and he was pleased to
observe the interest that his remarks had created. The he continued:

"The secret is lost. No one knows it. The legend is to the effect that
the former lords of the castle transmitted the secret from father to son
on their deathbeds, until Geoffroy, the last of the race, was beheaded
during the Revolution in his nineteenth year."

"That is over a century ago. Surely, someone has looked for it since
that time?"

"Yes, but they failed to find it. After I purchased the castle, I made a
diligent search for it, but without success. You must remember that this
tower is surrounded by water and connected with the castle only by a
bridge; consequently, the passage must be underneath the old moat. The
plan that was in the book in the National Library showed a series of
stairs with a total of forty-eight steps, which indicates a depth of
more than ten meters. You see, the mystery lies within the walls of this
room, and yet I dislike to tear them down."

"Is there nothing to show where it is?"

"Nothing."

"Mon. Devanne, we should turn our attention to the two quotations,"
suggested Father Gelis.

"Oh!" exclaimed Mon. Devanne, laughing, "our worthy father is fond
of reading memoirs and delving into the musty