The Duke shut the door and leant against it, listening anxiously, breathing quickly. There came the bang of the front door. With a deep sigh of relief he left the door, came briskly, smiling, across the room, and put the card-case back into the pocket of Guerchard's cloak. He lighted a cigarette, dropped into an easy chair, and sat waiting with an entirely careless air for the detective's return. Presently he heard quick footsteps on the bare boards of the empty room beyond the opening. Then Guerchard came down the steps and out of the fireplace.  
His face wore an expression of extreme perplexity:
 
"I can't understand it," he said. "I found nothing."
 
"Nothing?" said the Duke.
 
"No. Are you sure you saw the handkerchief in one of those little rooms on the second floor—quite sure?" said Guerchard.
 
"Of course I did," said the Duke. "Isn't it there?"
 
"No," said Guerchard.
 
"You can't have looked properly," said the Duke, with a touch of irony in his voice. "If I were you, I should go back and look again."
 
"No. If I've looked for a thing, I've looked for it. There's no need for me to look a second time. But, all the same, it's rather funny. Doesn't it strike you as being rather funny, your Grace?" said Guerchard, with a worried air.
 
"It strikes me as being uncommonly funny," said the Duke, with an ambiguous smile.
 
Guerchard looked at him with a sudden uneasiness; then he rang the bell.
 
Bonavent came into the room.
 
"Mademoiselle Kritchnoff, Bonavent. It's quite time," said Guerchard.
 
"Mademoiselle Kritchnoff?" said Bonavent, with an air of surprise.
 
"Yes, it's time that she was taken to the police-station."
 
"Mademoiselle Kritchnoff has gone, sir," said Bonavent, in a tone of quiet remonstrance.
 
"Gone? What do you mean by gone?" said Guerchard.
 
"Gone, sir, gone!" said Bonavent patiently.
 
"But you're mad.... Mad!" cried Guerchard.
 
"No, I'm not mad," said Bonavent. "Gone! But who let her go?" cried Guerchard.
 
"The men at the door," said Bonavent.
 
"The men at the door," said Guerchard, in a tone of stupefaction. "But she had to have my permit ... my permit on my card! Send the fools up to me!"
 
Bonavent went to the top of the staircase, and called down it. Guerchard followed him. Two detectives came hurrying up the stairs and into the drawing-room.
 
"What the devil do you mean by letting Mademoiselle Kritchnoff leave the house without my permit, written on my card?" cried Guerchard violently.
 
"But she had your permit, sir, and it WAS written on your card," stammered one of the detectives.
 
"It was? ... it was?" said Guerchard. "Then, by Jove, it was a forgery!"
 
He stood thoughtful for a moment. Then quietly he told his two men to go back to their post. He did not stir for a minute or two, puzzling it out, seeking light.
 
Then he came back slowly into the drawing-room and looked uneasily at the Duke. The Duke was sitting in his easy chair, smoking a cigarette with a listless air. Guerchard looked at him, and looked at him, almost as if he now saw him for the first time.
 
"Well?" said the Duke, "have you sent that poor child off to prison? If I'd done a thing like that I don't think I should sleep very well, M. Guerchard."
 
"That poor child has just escaped, by means of a forged permit," said Guerchard very glumly.
 
"By Jove, I AM glad to hear that!" cried the Duke. "You'll forgive my lack of sympathy, M. Guerchard; but she was such a child."
 
"Not too young to be Lupin's accomplice," said Guerchard drily.
 
"You really think she is?" said the Duke, in a tone of doubt.
 
"I'm sure of it," said Guerchard, with decision; then he added slowly, with a perplexed air:
 
"But how—how—could she get that forged permit?"
 
The Duke shook his head, and looked as solemn as an owl. Guerchard looked at him uneasily, went out of the drawing-room, and shut the door.
 
"How long has Mademoiselle Kritchnoff been gone?" he said to Bonavent.
 
"Not much more than five minutes," said Bonavent. "She came out from talking to you in the drawing-room—"
 
"Talking to me in the drawing-room!" exclaimed Guerchard.
 
"Yes," said Bonavent. "She came out and went straight down the stairs and out of the house."
 
A faint, sighing gasp came from Guerchard's lips. He dashed into the drawing-room, crossed the room quickly to his cloak, picked it up, took the card-case out of the pocket, and counted the cards in it. Then he looked at the Duke.
 
The Duke smiled at him, a charming smile, almost caressing.
 
There seemed to be a lump in Guerchard's throat; he swallowed it loudly.
 
He put the card-case into the breast-pocket of the coat he was wearing. Then he cried sharply, "Bonavent! Bonavent!"
 
Bonavent opened the door, and stood in the doorway.
 
"You sent off Victoire in the prison-van, I suppose," said Guerchard.
 
"Oh, a long while ago, sir," said Bonavent.
 
"The van had been waiting at the door since half-past nine."
 
"Since half-past nine? ... But I told them I shouldn't want it till a quarter to eleven. I suppose they were making an effort to be in time for once. Well, it doesn't matter," said Guerchard.
 
"Then I suppose I'd better send the other prison-van away?" said Bonavent.
 
"What other van?" said Guerchard.
 
"The van which has just arrived," said Bonavent.
 
"What! What on earth are you talking about?" cried Guerchard, with a sudden anxiety in his voice and on his face.
 
"Didn't you order two prison-vans?" said Bonavent.
 
Guerchard jumped; and his face went purple with fury and dismay. "You don't mean to tell me that two prison-vans have been here?" he cried.
 
"Yes, sir," said Bonavent.
 
"Damnation!" cried Guerchard. "In which of them did you put Victoire? In which of them?"
 
"Why, in the first, sir," said Bonavent.
 
"Did you see the police in charge of it? The coachman?"
 
"Yes, sir," said Bonavent.
 
"Did you recognize them?" said Guerchard.
 
"No," said Bonavent; "they must have been new men. They told me they came from the Sante."
 
"You silly fool!" said Guerchard through his teeth. "A fine lot of sense you've got."
 
"Why, what's the matter?" said Bonavent.
 
"We're done, done in the eye!" roared Guerchard. "It's a stroke—a stroke—"
 
"Of Lupin's!" interposed the Duke softly.
 
"But I don't understand," said Bonavent.
 
"You don't understand, you idiot!" cried Guerchard. "You've sent Victoire away in a sham prison-van—a prison-van belonging to Lupin. Oh, that scoundrel! He always has something up his sleeve."
 
"He certainly shows foresight," said the Duke. "It was very clever of him to foresee the arrest of Victoire and provide against it."
 
"Yes, but where is the leakage? Where is the leakage?" cried Guerchard, fuming. "How did he learn that the doctor said that she would recover her wits at ten o'clock? Here I've had a guard at the door all day; I've imprisoned the household; all the provisions have been received directly by a man of mine; and here he is, ready to pick up Victoire the very moment she gives herself away! Where is the leakage?"
 
He turned on Bonavent, and went on: "It's no use your standing there with your mouth open, looking like a fool. Go upstairs to the servants' quarters and search Victoire's room again. That fool of an inspector may have missed something, just as he missed Victoire herself. Get on! Be smart!"
 
Bonavent went off briskly. Guerchard paced up and down the room, scowling.
 
"Really, I'm beginning to agree with you, M. Guerchard, that this Lupin is a remarkable man," said the Duke. "That prison-van is extraordinarily neat."
 
"I'll prison-van him!" cried Guerchard. "But what fools I have to work with. If I could get hold of people of ordinary intelligence it would be impossible to play such a trick as that."
 
"I don't know about that," said the Duke thoughtfully. "I think it would have required an uncommon fool to discover that trick."
 
"What on earth do you mean? Why?" said Guerchard.
 
"Because it's so wonderfully simple," said the Duke. "And at the same time it's such infernal cheek."
 
"There's something in that," said Guerchard grumpily. "But then, I'm always saying to my men, 'Suspect everything; suspect everybody; suspect, suspect, suspect.' I tell you, your Grace, that there is only one motto for the successful detective, and that is that one word, 'suspect.'"
 
"It can't be a very comfortable business, then," said the Duke. "But I suppose it has its charms."
 
"Oh, one gets used to the disagreeable part," said Guerchard.
 
The telephone bell rang; and he rose and went to it. He put the receiver to his ear and said, "Yes; it's I—Chief-Inspector Guerchard."
 
He turned and said to the Duke, "It's the gardener at Charmerace, your Grace."
 
"Is it?" said the Duke indifferently.
 
Guerchard turned to the telephone. "Are you there?" he said. "Can you hear me clearly? ... I want to know who was in your hot-house yesterday ... who could have gathered some of your pink salvias?"
 
"I told you that it was I," said the Duke.
 
"Yes, yes, I know," said Guerchard. And he turned again to the telephone. "Yes, yesterday," he said. "Nobody else? ... No one but the Duke of Charmerace? ... Are you sure?... quite sure?... absolutely sure? ... Yes, that's all I wanted to know ... thank you."
 
He turned to the Duke and said, "Did you hear that, your Grace? The gardener says that you were the only person in his hot-houses yesterday, the only person who could have plucked any pink salvias."
 
"Does he?" said the Duke carelessly.
 
Guerchard looked at him, his brow knitted in a faint, pondering frown. Then the door opened, and Bonavent came in: "I've been through Victoire's room," he said, "and all I could find that might be of any use is this—a prayer-book. It was on her dressing-table just as she left it. The inspector hadn't touched it."
 
"What about it?" said Guerchard, taking the prayer-book.
 
"There's a photograph in it," said Bonavent. "It may come in useful when we circulate her description; for I suppose we shall try to get hold of Victoire."
 
Guerchard took the photograph from the prayer-book and looked at it: "It looks about ten years old," he said. "It's a good deal faded for reproduction. Hullo! What have we here?"
 
The photograph showed Victoire in her Sunday best, and with her a boy of seventeen or eighteen. Guerchard's eyes glued themselves to the face of the boy. He stared at it, holding the portrait now nearer, now further off. His eyes kept stealing covertly from the photograph to the face of the Duke.
 
The Duke caught one of those covert glances, and a vague uneasiness flickered in his eyes. Guerchard saw it. He came nearer to the Duke and looked at him e............