“About this time a little mystery suddenly clouded the normal routine of the professor’s life. He did what he had never done before. He left home and gave no indication where he was going. He was away a fortnight and returned looking rather travel-worn. He made no allusion to where he had been, although he was usually the frankest of men. It chanced, however, that our client here, Mr. Bennett, received a letter from a fellow-student in Prague, who said that he was glad to have seen Professor Presbury there, although he had not been able to talk to him. Only in this way did his own household learn where he had been.

“Now comes the point. From that time onward a curious change came over the professor. He became furtive and sly. Those around him had always the feeling that he was not the man that they had known, but that he was under some shadow which had darkened his higher qualities. His intellect was not affected. His lectures were as brilliant as ever. But always there was something new, something sinister and unexpected. His daughter, who was devoted to him, tried again and again to resume the old relations and to penetrate this mask which her father seemed to have put on. You, sir, as I understand, did the same — but all was in vain. vain And now, Mr. Bennett, tell in your own words the incident of the letters.”

“You must understand, Dr. Watson, that the professor had no secrets from me. If I were his son or his younger brother I could not have more completely enjoyed his confidence. As his secretary I handled every paper which came to him, and I opened and subdivided his letters. Shortly after his return all this was changed. He told me that certain letters might come to him from London which would be marked by a cross under the stamp. These were to be set aside for his own eyes only. I may say that several of these did pass through my hands, that they had the E. C. mark, and were in an illiterate handwriting. If he answered them at all the answers did not pass through my hands nor into the letter-basket in which our correspondence was collected.”

“And the box,” said Holmes.

“Ah, yes, the box. The professor brought back a little wooden box from his travels. It was the one thing which suggested a Continental tour, for it was one of those quaint carved things which one associates with Germany. This he placed in his instrument cupboard. One day, in looking for a canula, I took up the box. To my surprise he was very angry, and reproved me in words which were quite savage for my curiosity. It was the first time such a thing had happened, and I was deeply hurt. I endeavoured to explain that it was a mere accident that I had touched the box, but all the evening I was conscious that he looked at me harshly and that the incident was rankling in his mind.” Mr. Bennett drew a little diary book from his pocket. “That was on July 2d,” said he.

“You are certainly an admirable witness,” said Holmes. “I may need some of these dates which you have noted.”

"The house in the Square Lamartine is occupied by Prasville's men."

"Don't worry, Sebastiani. I shall get in. If they don't open the door, there's always the window. And, if the window won't open, I shall arrange with one of Prasville's men. It's a question of money, that's all. And, thank goodness, I shan't be short of that, henceforth! Good-night, Daubrecq."

He went out, accompanied by Sebastiani, and the heavy door closed after them.

Lupin at once effected his retreat, in accordance with a plan which he had worked out during this scene.

The plan was sunple enough: to scramble, by means of his rope, to the bottom of the cliff, take his friends with him, jump into the motor-car and attack d'Albufex and Sebastiani on the deserted road that leads to Aumale Station. There could be no doubt about the issue of the contest. With d'Albufex and Sebastiani prisoners; it would be an easy matter to make one of them speak. D'Albufex had shown him how to set about it; and Clarisse Mergy would be inflexible where it was a question of saving her son.

He took the rope with which he had provided himself and groped about to find a jagged piece of rock round which to pass it, so as to leave two equal lengths hanging, by which he could let himself down. But, when he found what he wanted, instead of acting swiftly - for the business was urgent - he stood motionless, thinking. His scheme failed to satisfy him at the last moment.

"It's absurd, what I'm proposing," he said to himself. "Absurd and illogical. How can I tell that d'Albufex and Sebastiani will not escape me? How can I even tell that, once they are in my power, they will speak? No, I shall stay. There are better things to try... much better things. It's not those two I must be at, but Daubrecq. He's done for; he has not a kick left in him. If he has told the marquis his secret, there is no reason why he shouldn't tell it to Clarisse and me, when we employ the same methods. That's settled! We'll kidnap the Daubrecq bird." And he continued, "Besides, what do I risk? If the scheme miscarries, Clarisse and I will rush off to Paris and, together with Prasville, organize a careful watch in the Square Lamartine to prevent d'Albufex from benefiting by Daubrecq's revelations. The great thing is for Prasville to be warned of the danger. He shall be."

The church-clock in a neighbouring village struck twelve. That gave Lupin six or seven hours to put his new plan into execution. He set to work forthwith.

When moving away from the embrasure which had the window at the bottom of it, he had come upon a clump of small shrubs in one of the hollows of the cliff. He cut away a dozen of these, with his knife, and whittled them all down to the same size. Then he cut off two equal lengths from his rope. These were the uprights of the ladder. He fastened the twelve little sticks between the uprights and thus contrived a rope-ladder about six yards long.

When he returned to this post, there was only one of the three sons beside Daubrecq's bed in the torture-chamber. He was smoking his pipe by the lamp. Daubrecq was asleep.