When Guerchard joined the Duke in the drawing-room, he had lost his calm air and was looking more than a little nervous. He moved about the room uneasily, fingering the bric-a-brac, glancing at the Duke and looking quickly away from him again. Then he came to a standstill on the hearth-rug with his back to the fireplace.  
"Do you think it's quite safe to stand there, at least with your back to the hearth? If Lupin dropped through that opening suddenly, he'd catch you from behind before you could wink twice," said the Duke, in a tone of remonstrance.
 
"There would always be your Grace to come to my rescue," said Guerchard; and there was an ambiguous note in his voice, while his piercing eyes now rested fixed on the Duke's face. They seemed never to leave it; they explored, and explored it.
 
"It's only a suggestion," said the Duke.
 
"This is rather nervous work, don't you know."
 
"Yes; and of course you're hardly fit for it," said Guerchard. "If I'd known about your break-down in your car last night, I should have hesitated about asking you—"
 
"A break-down?" interrupted the Duke.
 
"Yes, you left Charmerace at eight o'clock last night. And you only reached Paris at six this morning. You couldn't have had a very high-power car?" said Guerchard.
 
"I had a 100 h.-p. car," said the Duke.
 
"Then you must have had a devil of a break-down," said Guerchard.
 
"Yes, it was pretty bad, but I've known worse," said the Duke carelessly. "It lost me about three hours: oh, at least three hours. I'm not a first-class repairer, though I know as much about an engine as most motorists."
 
"And there was nobody there to help you repair it?" said Guerchard.
 
"No; M. Gournay-Martin could not let me have his chauffeur to drive me to Paris, because he was keeping him to help guard the chateau. And of course there was nobody on the road, because it was two o'clock in the morning."
 
"Yes, there was no one," said Guerchard slowly.
 
"Not a soul," said the Duke.
 
"It was unfortunate," said Guerchard; and there was a note of incredulity in his voice.
 
"My having to repair the car myself?" said the Duke.
 
"Yes, of course," said Guerchard, hesitating a little over the assent.
 
The Duke dropped the end of his cigarette into a tray, and took out his case. He held it out towards Guerchard, and said, "A cigarette? or perhaps you prefer your caporal?"
 
"Yes, I do, but all the same I'll have one," said Guerchard, coming quickly across the room. And he took a cigarette from the case, and looked at it.
 
"All the same, all this is very curious," he said in a new tone, a challenging, menacing, accusing tone.
 
"What?" said the Duke, looking at him curiously.
 
"Everything: your cigarettes ... the salvias ... the photograph that Bonavent found in Victoire's prayer-book ... that man in motoring dress ... and finally, your break-down," said Guerchard; and the accusation and the threat rang clearer.
 
The Duke rose from his chair quickly and said haughtily, in icy tones: "M. Guerchard, you've been drinking!"
 
He went to the chair on which he had set his overcoat and his hat, and picked them up. Guerchard sprang in front of him, barring his way, and cried in a shaky voice: "No; don't go! You mustn't go!"
 
"What do you mean?" said the Duke, and paused. "What DO you mean?"
 
Guerchard stepped back, and ran his hand over his forehead. He was very pale, and his forehead was clammy to his touch:
 
"No ... I beg your pardon ... I beg your pardon, your Grace ... I must be going mad," he stammered.
 
"It looks very like it," said the Duke coldly.
 
"What I mean to say is," said Guerchard in a halting, uncertain voice, "what I mean to say is: help me ... I want you to stay here, to help me against Lupin, you understand. Will you, your Grace?"
 
"Yes, certainly; of course I will, if you want me to," said the Duke, in a more gentle voice. "But you seem awfully upset, and you're upsetting me too. We shan't have a nerve between us soon, if you don't pull yourself together."
 
"Yes, yes, please excuse me," muttered Guerchard.
 
"Very good," said the Duke. "But what is it we're going to do?"
 
Guerchard hesitated. He pulled out his handkerchief, and mopped his forehead: "Well ... the coronet ... is it in this case?" he said in a shaky voice, and set the case on the table.
 
"Of course it is," said the Duke impatiently.
 
Guerchard opened the case, and the coronet sparkled and gleamed brightly in the electric light: "Yes, it is there; you see it?" said Guerchard.
 
"Yes, I see it; well?" said the Duke, looking at him in some bewilderment, so unlike himself did he seem.
 
"We're going to wait," said Guerchard.
 
"What for?" said the Duke.
 
"Lupin," said Guerchard.
 
"Lupin? And you actually do believe that, just as in a fairy tale, when that clock strikes twelve, Lupin will enter and take the coronet?"
 
"Yes, I do; I do," said Guerchard with stubborn conviction. And he snapped the case to.
 
"This is most exciting," said the Duke.
 
"You're sure it doesn't bore you?" said Guerchard huskily.
 
"Not a bit of it," said the Duke, with cheerful derision. "To make the acquaintance of this scoundrel who has fooled you for ten years is as charming a way of spending the evening as I can think of."
 
"You say that to me?" said Guerchard with a touch of temper.
 
"Yes," said the Duke, with a challenging smile. "To you."
 
He sat down in an easy chair by the table. Guerchard sat down in a chair on the other side of it, and set his elbows on it. They were silent.
 
Suddenly the Duke said, "Somebody's coming."
 
Guerchard started, and said: "No, I don't hear any one."
 
Then there came distinctly the sound of a footstep and a knock at the door.
 
"You've got keener ears than I," said Guerchard grudgingly. "In all this business you've shown the qualities of a very promising detective." He rose, went to the door, and unlocked it.
 
Bonavent came in: "I've brought you the handcuffs, sir," he said, holding them out. "Shall I stay with you?"
 
"No," said Guerchard. "You've two men at the back door, and two at the front, and a man in every room on the ground-floor?"
 
"Yes, and I've got three men on every other floor," said Bonavent, in a tone of satisfaction.
 
"And the house next door?" said Guerchard.
 
"There are a dozen men in it," said Bonavent. "No communication between the two houses is possible any longer."
 
Guerchard watched the Duke's face with intent eyes. Not a shadow flickered its careless serenity.
 
"If any one tries to enter the house, collar him. If need be, fire on him," said Guerchard firmly. "That is my order; go and tell the others."
 
"Very good, sir," said Bonavent; and he went out of the room.
 
"By Jove, we are in a regular fortress," said the Duke.
 
"It's even more of a fortress than you think, your Grace. I've four men on that landing," said Guerchard, nodding towards the door.
 
"Oh, have you?" said the Duke, with a sudden air of annoyance.
 
"You don't like that?" said Guerchard quickly.
 
"I should jolly well think not," said the Duke. "With these precautions, Lupin will never be able to get into this room at all."
 
"He'll find it a pretty hard job," said Guerchard, smiling. "Unless he falls from the ceiling, or unless—"
 
"Unless you're Arsene Lupin," interrupted the Duke.
 
"In that case, you'd be another, your Grace," said Guerchard.
 
They both laughed. The Duke rose, yawned, picked up his coat and hat, and said, "Ah, well, I'm off to bed."
 
"What?" said Guerchard.
 
"Well," said the Duke, yawning again, "I was staying to see Lupin. As there's no longer any chance of seeing him—"
 
"But there is ... there is ... so stay," cried Guerchard.
 
"Do you still cling to that notion?" said the Duke wearily.
 
"We SHALL see him," said Guerchard.
 
"Nonsense!" said the Duke.
 
Guerchard lowered his voice and said with an air of the deepest secrecy: "He's already here, your Grace."
 
"Lupin? Here?" cried the Duke.
 
"Yes; Lupin," said Guerchard.
 
"Where?" cried the astonished Duke.
 
"He is," said Guerchard.
 
"As one of your men?" said the Duke eagerly.
 
"I don't think so," said Guerchard, watching him closely.
 
"Well, but, well, but—if he's here we've got him.... He is going to turn up," said the Duke triumphantly; and he set down his hat on the table beside the coronet.
 
"I hope so," said Guerchard. "But will he dare to?"
 
"How do you mean?" said the Duke, with a puzzled air.
 
"Well, you have said yourself that this is a fortress. An hour ago, perhaps, Lupin was resolved to enter this room, but is he now?"
 
"I see what you mean," said the Duke, in a tone of disappointment.
 
"Yes; you see that now it needs the devil's own courage. He must risk everything to gain everything, and throw off the mask. Is Lupin going to throw himself into the wolf's jaws? I dare not think it. What do you think about it?"
 
Guerchard's husky voice had hardened to a rough harshness; there was a ring of acute anxiety in it, and under the anxiety a faint note of challenge, of a challenge that dare not make itself too distinct. His anxious, challenging eyes burned on the face of the Duke, as if they strove with all intensity to pierce a mask.
 
The Duke looked at him curiously, as if he were trying to divine what he would be at, but with a careless curiosity, as if it were a matter of indifference to him what the detective's object was; then he said carelessly: "Well, you ought to know better than I. You have known him for ten years ...." He paused, and added with just the faintest stress in his tone, "At least, by reputation."
 
The anxiety in the detective's face grew plainer, it almost gave him the air of being unnerved; and he said quickly, in a jerky voice: "Yes, and I know his way of acting too. During the last ten years I have learnt to unravel his intrigues—to understand and anticipate his manoeuvres.... Oh, his is a clever system! ... Instead of lying low, as you'd expect, he attacks his opponent ... openly.... He confuses him—at least, he tries to." He smiled a half-confident, a half-doubtful smile, "It is a mass of entangled, mysterious combinations. I've been caught in them myself again and again. You smile?"
 
"It interests me so," said the Duke, in a tone of apology.
 
"Oh, it interests me," said Guerchard, with a snarl. "But this time I see my way clearly. No more tricks—no more secret paths ... We're fighting in the light of day." He paused, and said in a clear, sneering voice, "Lupin has pluck, perhaps, but it's only thief's pluck."
 
"Oh, is it?" said the Duke sharply, and there was a sudden faint glitter in his eyes.
 
"Yes; rogues have very poor qualities," sneered Guerchard.
 
"One can't have everything," said the Duke quietly; but his languid air had fallen from him.
 
"Their ambushes, their attacks, their fine tactics aren't up to much," said Guerchard, smiling contemptuously.
 
"You go a trifle too far, I think," said the Duke, smiling with equal contempt.
 
They looked one another in the eyes with a long, lingering look. They had suddenly the air of fencers who have lost their tempers, and are twisting the buttons off their foils.
 
"Not a bit of it, your Grace," said Guerchard; and his voice lingered on the words "your Grace" with a contemptuous stress. "This famous Lupin is immensely overrated."
 
"However, he has done some things which aren't half bad," said the Duke, with his old charming smile.
 
He had the air of a duelist drawing his blade lovingly through his fingers before............