Leaving a policeman on guard at the door of the drawing-room M. Formery, the Duke, and the inspector set out on their tour of inspection. It was a long business, for M. Formery examined every room with the most scrupulous care—with more care, indeed, than he had displayed in his examination of the drawing-rooms. In particular he lingered long in the bedroom of Victoire, discussing the possibilities of her having been murdered and carried away by the burglars along with their booty. He seemed, if anything, disappointed at finding no blood-stains, but to find real consolation in the thought that she might have been strangled. He found the inspector in entire agreement with every theory he enunciated, and he grew more and more disposed to regard him as a zealous and trustworthy officer. Also he was not at all displeased at enjoying this opportunity of impressing the Duke with his powers of analysis and synthesis. He was unaware that, as a rule, the Duke's eyes did not usually twinkle as they twinkled during this solemn and deliberate progress through the house of M. Gournay-Martin. M. Formery had so exactly the air of a sleuthhound; and he was even noisier.
 
Having made this thorough examination of the house, M. Formery went out into the garden and set about examining that. There were footprints on the turf about the foot of the ladder, for the grass was close-clipped, and the rain had penetrated and softened the soil; but there were hardly as many footprints as might have been expected, seeing that the burglars must have made many journeys in the course of robbing the drawing-rooms of so many objects of art, some of them of considerable weight. The footprints led to a path of hard gravel; and M. Formery led the way down it, out of the door in the wall at the bottom of the garden, and into the space round the house which was being built.
 
As M. Formery had divined, there was a heap, or, to be exact, there were several heaps of plaster about the bottom of the scaffolding. Unfortunately, there were also hundreds of footprints. M. Formery looked at them with longing eyes; but he did not suggest that the inspector should hunt about for a set of footprints of the size of the one he had so carefully measured on the drawing-room carpet.
 
While they were examining the ground round the half-built house a man came briskly down the stairs from the second floor of the house of M. Gournay-Martin. He was an ordinary-looking man, almost insignificant, of between forty and fifty, and of rather more than middle height. He had an ordinary, rather shapeless mouth, an ordinary nose, an ordinary chin, an ordinary forehead, rather low, and ordinary ears. He was wearing an ordinary top-hat, by no means new. His clothes were the ordinary clothes of a fairly well-to-do citizen; and his boots had been chosen less to set off any slenderness his feet might possess than for their comfortable roominess. Only his eyes relieved his face from insignificance. They were extraordinarily alert eyes, producing in those on whom they rested the somewhat uncomfortable impression that the depths of their souls were being penetrated. He was the famous Chief-Inspector Guerchard, head of the Detective Department of the Prefecture of Police, and sworn foe of Arsene Lupin.
 
The policeman at the door of the drawing-room saluted him briskly. He was a fine, upstanding, red-faced young fellow, adorned by a rich black moustache of extraordinary fierceness.
 
"Shall I go and inform M. Formery that you have come, M. Guerchard?" he said.
 
"No, no; there's no need to take the trouble," said Guerchard in a gentle, rather husky voice. "Don't bother any one about me—I'm of no importance."
 
"Oh, come, M. Guerchard," protested the policeman.
 
"Of no importance," said M. Guerchard decisively. "For the present, M. Formery is everything. I'm only an assistant."
 
He stepped into the drawing-room and stood looking about it, curiously still. It was almost as if the whole of his being was concentrated in the act of seeing—as if all the other functions of his mind and body were in suspension.
 
"M. Formery and the inspector have just been up to examine the housekeeper's room. It's right at the top of the house—on the second floor. You take the servants' staircase. Then it's right at the end of the passage on the left. Would you like me to take you up to it, sir?" said the policeman eagerly. His heart was in his work.
 
"Thank you, I know where it is—I've just come from it," said Guerchard gently.
 
A grin of admiration widened the already wide mouth of the policeman, and showed a row of very white, able-looking teeth.
 
"Ah, M. Guerchard!" he said, "you're cleverer than all the examining magistrates in Paris put together!"
 
"You ought not to say that, my good fellow. I can't prevent you thinking it, of course; but you ought not to say it," said Guerchard with husky gentleness; and the faintest smile played round the corners of his mouth.
 
He walked slowly to the window, and the policeman walked with him.
 
"Have you noticed this, sir?" said the policeman, taking hold of the top of the ladder with a powerful hand. "It's probable that the burglars came in and went away by this ladder."
 
"Thank you," said Guerchard.
 
"They have even left this card-table on the window-sill," said the policeman; and he patted the card-table with his other powerful hand.
 
"Thank you, thank you," said Guerchard.
 
"They don't think it's Lupin's work at all," said the policeman. "They think that Lupin's letter announcing the burglary and these signatures on the walls are only a ruse."
 
"Is that so?" said Guerchard.
 
"Is there any way I can help you, sir?" said policeman.
 
"Yes," said Guerchard. "Take up your post outside that door and admit no one but M. Formery, the inspector, Bonavent, or Dieusy, without consulting me." And he pointed to the drawing-room door.
 
"Shan't I admit the Duke of Charmerace? He's taking a great interest in this affair," said the policeman.
 
"The Duke of Charmerace? Oh, yes—admit the Duke of Charmerace," said Guerchard.
 
The policeman went to his post of responsibility, a proud man.
 
Hardly had the door closed behind him when Guerchard was all activity—activity and eyes. He examined the ladder, the gaps on the wall from which the pictures had been taken, the signatures of Arsene Lupin. The very next thing he did was to pick up the book which the Duke had set on the top of the footprint again, to preserve it; and he measured, pacing it, the distance between the footprint and the window.
 
The result of this measuring did not appear to cause him any satisfaction, for he frowned, measured the distance again, and then stared out of the window with a perplexed air, thinking hard. It was curious that, when he concentrated himself on a process of reasoning, his eves seemed to lose something of their sharp brightness and grew a little dim.
 
At last he seemed to come to some conclusion. He turned away from the window, drew a small magnifying-glass from his pocket, dropped on his hands and knees, and began to examine the surface of the carpet with the most minute care.
 
He examined a space of it nearly six feet square, stopped, and gazed round the room. His eyes rested on the fireplace, which he could see under the bottom of the big tapestried fire-screen which was raised on legs about a foot high, fitted with big casters. His eyes filled with interest; without rising, he crawled quickly across the room, peeped round the edge of the screen and rose, smiling.
 
He went on to the further drawing-room and made the same careful examination of it, again examining a part of the surface of the carpet with his magnifying-glass. He came back to the window to which the ladder had been raised and examined very carefully the broken shutter. He whistled softly to himself, lighted a cigarette, and leant against the side of the window. He looked out of it, with dull eyes which saw nothing, the while his mind worked upon the facts he had discovered.
 
He had stood there plunged in reflection for perhaps ten minutes, when there came a sound of voices and footsteps on the stairs. He awoke from his absorption, seemed to prick his ears, then slipped a leg over the window-ledge, and disappeared from sight down the ladder.
 
The door opened, and in came M. Formery, the Duke, and the inspector. M. Formery looked round the room with eyes which seemed to expect to meet a familiar sight, then walked to the other drawing-room and looked round that. He turned to the policeman, who had stepped inside the drawing-room, and said sharply, "M. Guerchard is not here."
 
"I left him here," said the policeman. "He must have disappeared. He's a wonder."
 
"Of course," said M. Formery. "He has gone down the ladder to examine that house they're building. He's just following in our tracks and doing all over again the work we've already done. He might have saved himself the trouble. We could have told him all he wants to know. But there! He very likely would not be satisfied till he had seen everything for himself."
 
"He may see something which we have missed," said the Duke.
 
M. Formery frowned, and said sharply "That's hardly likely. I don't think that your Grace realizes to what a perfection constant practice brings one's power of observation. The inspector and I will cheerfully eat anything we've missed—won't we, inspector?" And he laughed heartily at his joke.
 
"It might always prove a large mouthful," said the Duke with an ironical smile.
 
M. Formery assumed his air of profound reflection, and walked a few steps up and down the room, frowning:
 
"The more I think about it," he said, "the clearer it grows that we have disposed of the Lupin theory. This is the work of far less expert rogues than Lupin. What do you think, inspector?"
 
"Yes; I think you have disposed of that theory, sir," said the inspector with ready acquiescence.
 
"All the same, I'd wager anything that we haven't disposed of it to the satisfaction of Guerchard," said M. Formery.
 
"Then he must be very hard to satisfy," said the Duke.
 
"Oh, in any other matter he's open to reason," said M. Formery; "but Lupin is his fixed idea; it's an obsession—almost a mania."
 
"But yet he never catches him," said the Duke.
 
"No; and he never will. His very obsession by Lupin hampers him. It cramps his mind and hinders its working," said M. Formery.
 
He resumed his meditative pacing, stopped again, and said:
 
"But considering everything, especially the absence of any traces of violence, combined with her entire disappearance, I have come to another conclusion. Victoire is the key to the mystery. She is the accomplice. She never slept in her bed. She unmade it to put us off the scent. That, at any rate, is something gained, to have found the accomplice. We shall have this good news, at least, to tell M, Gournay-Martin on his arrival."
 
"Do you really think that she's the ............