archives of the castle.
Everything relating to Thibermesnil interests him greatly. But the
quotations that he mentions only serve to complicate the mystery. He
has read somewhere that two kings of France have known the key to the
puzzle."

"Two kings of France! Who were they?"

"Henry the Fourth and Louis the Sixteenth. And the legend runs like
this: On the eve of the battle of Arques, Henry the Fourth spent the
night in this castle. At eleven o'clock in the evening, Louise de
Tancarville, the prettiest woman in Normandy, was brought into the
castle through the subterranean passage by Duke Edgard, who, at the
same time, informed the king of the secret passage. Afterward, the king
confided the secret to his minister Sully, who, in turn, relates the
story in his book, "Royales Economies d'Etat," without making any
comment upon it, but linking with it this incomprehensible sentence:
`Turn one eye on the bee that shakes, the other eye will lead to God!'"

After a brief silence, Velmont laughed and said:

"Certainly, it doesn't throw a dazzling light upon the subject."

"No; but Father Gelis claims that Sully concealed the key to the
mystery in this strange sentence in order to keep the secret from the
secretaries to whom he dictated his memoirs."

"That is an ingenious theory," said Velmont.

"Yes, and it may be nothing more; I cannot see that it throws any light
on the mysterious riddle."

"And was it also to receive the visit of a lady that Louis the Sixteenth
caused the passage to be opened?"

"I don't know," said Mon. Devanne. "All I can say is that the king
stopped here one night in 1784, and that the famous Iron Casket found
in the Louvre contained a paper bearing these words in the king's own
writing: `Thibermesnil 3-4-11.'"

Horace Velmont laughed heartily, and exclaimed:

"At last! And now that we have the magic key, where is the man who can
fit it to the invisible lock?"

"Laugh as much as you please, monsieur," said Father Gelis, "but I am
confident the solution is contained in those two sentences, and some day
we will find a man able to interpret them."

"Sherlock Holmes is the man," said Mon. Devanne, "unless Arsene Lupin
gets ahead of him. What is your opinion, Velmont?"

Velmont arose, placed his hand on Devanne's shoulder, and declared:

"I think that the information furnished by your book and the book of the
National Library was deficient in a very important detail which you have
now supp