“Well, the police investigated the matter, and, as usual, discovered no clue whatever.”
“They never do, when Arsène 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 Arsène Lupin.”
“What glory for Arsène 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. Then 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?”