Devanne did so, and, to his great surprise, it produced a clicking sound.
“Quite right,” said Holmes. “Now, we will go to the other end of the word ‘Thibermesnil,’ try the letter I, and see if it will open like a wicket.”
With a certain degree of solemnity, Devanne seized the letter. It opened, but Devanne fell from the ladder, for the entire section of the bookcase, lying between the first and last letters of the words, turned on a pivot and disclosed the subterranean passage.
Sherlock Holmes said, coolly:
“You are not hurt?”
“No, no,” said Devanne, as he rose to his feet, “not hurt, only bewildered. I can’t understand now … those letters turn … the secret passage opens. …”
“Certainly. Doesn’t that agree exactly with the formula given by Sully? Turn one eye on the bee that shakes, the other eye will lead to God.”
“But Louis the sixteenth?” asked Devanne.
“Louis the sixteenth was a clever locksmith. I have read a book he wrote about combination locks. It was a good idea on the part of the owner of Thibermesnil to show His Majesty a clever bit of mechanism. As an aid to his memory, the king wrote: 3–4–11, that is to say, the third, fourth and eleventh letters of the word.”
“Exactly. I understand that. It explains how Lupin got out of the room, but it does not explain how he entered. And it is certain he came from the outside.”
Sherlock Holmes lighted his lantern, and stepped into the passage.
“Look! All the mechanism is exposed here, like the works of a clock, and the reverse side of the letters can be reached. Lupin worked the combination from this side—that is all.”
“What proof is there of that?”
“Proof? Why, look at that puddle of oil. Lupin foresaw that the wheels would require oiling.”
“Did he know about the other entrance?”
“As well as I know it,” said Holmes. “Follow me.”
“Into that dark passage?”
“Are you afraid?”
“No, but are you sure you can find the way out?”
“With my eyes closed.”
At first, they descended twelve steps, then twelve more, and, farther on, two other flights of twelve steps each. Then they walked through a long passageway, the brick walls of which showed the marks of successive restorations, and, in spots, were dripping with water. The earth, also, was very damp.
“We are passing under the pond,” said Devanne, somewhat nervously.
At last, they came to a stairway of twelve steps, followed by three others of twelve steps each, which they mounted with difficulty, and then found themselves in a small cavity cut in the rock. They could go no further.
“The deuce!” muttered Holmes, “nothing but bare walls. This is provoking.”
“Let us go back,” said Devanne. “I have seen enough to satisfy me.”
But the Englishman raised his eye and uttered a sigh of relief. There, he saw the same mechanism and the same word as before. He had merely to work the three letters. He did so, and a block of granite swung out of place. On the other side, this granite block formed the tombstone of Duke Rollo, and the word “Thibermesnil” was engraved on it in relief. Now, they were in the little ruined chapel, and the detective said:
“The other eye leads to God; that means, to the chapel.”
“It is marvelous!” exclaimed Devanne, amazed at the clairvoyance and vivacity of the Englishman. “Can it be possible that those few words were sufficient for you?”
“Bah!” declared Holmes, “they weren’t even necessary. In the chart in the book of the National Library, the drawing terminates at the left, as you know, in a circle, and at the right, as you do not know, in a cross. Now, that cross must refer to the chapel in which we now stand.”
Poor Devanne could not believe his ears. It was all so new, so novel to him. He exclaimed:
“It is incredible, miraculous, and yet of a childish simplicity! How is it that no one has ever solved the mystery?”
“Because no one has ever united the essential elements, that is to say, the two books and the two sentences. No one, but Arsène Lupin and myself.”
“But, Father Gélis and I knew all about those things, and, likewise—”
Holmes smiled, and said:
“Monsieur Devanne, everybody cannot solve riddles.”
“I have been trying for ten years to accomplish what you did in ten minutes.”
“Bah! I am used to it.”
They emerged from the chapel, and found an automobile.
“Ah! there’s an auto waiting for us.”
“Yes, it is mine,” said Devanne.
“Yours? You said your chauffeur hadn’t returned.”
“That is right. I wonder how it came—”
They approached the machine, and Mon. Devanne questioned the chauffer:
“Édouard, who gave you orders to come here?”
“Why, it was Monsieur Velmont.”
“Mon. Velmont? Did you meet him?”
“Near the railway station, and he told me to come to the chapel.”
“To come to the chapel! What for?”
“To wait for you, monsieur, and your friend.”
Devanne and Holmes exchanged looks, and Mon. Devanne said:
“He knew the mystery would be a simple one for you. It is a delicate compliment.”
A smile of satisfaction lighted up the detective’s serious features for a moment. The compliment pleased him. He shook his head, as he said:
“A clever man! I knew that when I saw him.”
“Have you seen him?”
“I met him a short time ago—on my way from the station.”
“And you knew it was Horace Velmont—I mean, Arsène Lupin?”
“No, but I supposed it was—from a certain ironical speech he made.”
“And you allowed him to escape?”
“Of course I did. And yet I had everything on my side, such as five gendarmes who passed us.”
“Sacrableu!” cried Devanne. “You should have taken advantage of the opportunity.”
“Really, monsieur,” said the Englishman, haughtily, “when I encounter an adversary like Arsène Lupin, I do not take advantage of chance opportunities, I create them.”
But time pressed, and since Lupin had been so kind as to send the automobile, they resolved to profit by it. They seated themselves in the comfortable limousine; Édouard took his place at the wheel, and away they went toward the railway station. Suddenly, Devanne’s eyes fell upon a small package in one of the pockets of the carriage.
“Ah!
