"As a matter of fact, Monsieur Juve, did not the celebrated Vidocq before he was a detective begin life as a murderer?"

Wulf, book in hand and comfortably installed in a large armchair, addressed the question to Juve, who answered in brief monosyllables, without turning his head:

"That's true, Monsieur Wulf."

"And don't you think that every detective at one time or another has a tendency toward crime, either as a thief or as an assassin?"

"That I cannot say."

What a day Juve had passed! Events had succeeded each other with such startling rapidity that the detective, in spite of his robust physique, began at length to feel the strain. As a matter of fact he had really had no rest since his tragic awakening in the mortuary chapel at Glotzbourg. He had passed the following night in the train without closing an eye. Upon his arrival he had been busy without interruption until he found himself, at ten o'clock at night, in his little apartment in the Rue Bonaparte with the grotesque Wulf as companion. While the latter was tranquilly reading the adventures of Vidocq, Juve was absorbed in a strange task which occupied his entire attention.

He was minutely examining a queer-looking garment, a waistcoat of very unusual cut. He turned to Wulf:

"Monsieur Wulf, you recognize this garment, don't you? There is no doubt that it came from Jacob and Company, the Glotzbourg tailors?"

Wulf nodded.

"No doubt whatever. I've had too much experience in such matters to be mistaken.... Besides, the initials J. G. are on the buttons."

"Yes, yes—Jacob of Glotzbourg."

Juve now examined the lining with a magnifying glass, muttering the while:

"Ah, just as I expected!"

The pocket of the waistcoat had been distended by some large object which had been forcibly introduced into it. The detective quickly took some modeling clay and made it into certain dimensions carefully measured, then with a stick he marked the surface of the ball into facets, referring now and again to a book open before him. "Let's see," he exclaimed, "the Hesse-Weimar diamond is two-thirds of a hen's egg in size, and weighs 295 carats, that is to say, larger than the Koh-i-noor, the famous Indian diamond, one of the crown jewels of England."

He now introduced his model into the pocket and found that it fitted the hole exactly.

"There! What do you say to that!" he cried.

"Why, you're very clever, Monsieur Juve," replied Wulf, "but I don't see how that helps. Even if you prove that the King's diamond was kept for a certain time in the pocket of that waistcoat, still you don't know to whom the waistcoat belongs, and that's the most important point."

Juve, still engrossed in his examination, vouchsafed no reply, and Wulf with folded arms stood contemplating him. Various problems were engaging Juve's thoughts, whose day had been exceedingly busy.

After being satisfied that Frederick-Christian was really back again at the Royal Palace, the question arose as to what had become of him after his disappearance. A hurried visit to Fandor's lodgings disclosed the fact that the journalist, after a brief absence, had returned home for an hour and had then disappeared again.

"Upon my word," he thought, "he might at least have sent me some word. He must know how anxious I would be about him."

From Fandor's house Juve had gone direct to Susy d'Orsel's apartment. It was a theory of his that a good detective could never visit too often the scene of a crime. Mechanically he went through the various rooms until he reached the kitchen.

"I have a feeling that something happened here," he muttered, "but what?"

A close examination of the floor showed distinct traces of feet in some fine coal dust. These traces proved to be those of a woman's shoes, small, elegant and well made. They could not possibly belong to Mother Citron nor to Susy d'Orsel, who, he recalled, had worn satin mules on the night of the murder. The person who immediately presented herself to Juve's mind was Marie Pascal.

"The deuce!" he cried, "this becomes complicated. This coal dust and these imprints were not here a few days ago, therefore some one has been here since and has evidently been at pains to lay a false trail!"

With the intention of examining the servants' staircase again, he let himself out with a pass-key and began the descent. But so absorbed was he in his thoughts that unconsciously he went down one flight too many and found himself in the cellar of the building. Juve, following his custom of never neglecting to search even the most unsuspicious places, lit his electric light and examined the room he had entered.

On either side of the cellar were ranged a number of doors, all securely padlocked. These were evidently the private cellars of the tenants. As he threw his light on the floor, he could not repress a movement of surprise. Dropping on all fours, he began a close examination of the ground.

"Now I begin to see daylight. For some time I have had the conviction that Frederick-Christian, upon leaving Fandor made his escape by the servants' staircase, and thus left the house. But I could not understand why he had not returned to his hotel. My conclusion was wrong. Frederick-Christian, like myself, came down a flight too many and found himself, as I have, in this cellar. Evidently a scoundrel was waiting for him here. The trampled ground, the shreds of silk torn from a high hat, all indicate clearly the struggle which took place. But the King, being drunk, was easily overpowered and bound. That is the reason he did not reach his hotel."

One difficulty still troubled the detective. It had been shown that on the night of December 31st, the third person, otherwise the King, whom Fandor declared to be in the apartment, had been unable to escape by the back stairs, since the door was locked and bolted. Then it came into Juve's mind that the maid Justine in giving testimony had become embarrassed and finally had admitted that the key having been lost, she had neglected to lock the door. This cleared up the dubious point and established in Juve's mind the complete explanation of what happened.

FantÔmas, after killing Susy d'Orsel, had lurked on the stairs until the King left the apartment. Then, locking the door, he had hurried after his victim and caught him at the moment he reached the cellar.

The detective's next move was to break into the apartment of the Marquis de SÉrac. By the aid of a ladder which he found in a corner, he climbed up and broke a windowpane and thus made his entrance. At first nothing in the apartment seemed worthy of suspicion. The rooms were elegant but commonplace. The bureaus and wardrobes were locked, and gave out a hollow sound when rapped upon. As he did not have his burglar's equipment with him, Juve decided to come back later and investigate. He was on the point of leaving when his foot caught in a garment, which he found to be a waistcoat. He gave vent to an exclamation of surprise as he picked it up and folding it into a bundle hid it under his overcoat. The Marquis de SÉrac had been under his suspicion for some time; now that suspicion was in a fair way to become a certainty. Were the Marquis and FantÔmas one and the same?

Juve was inclined to answer in the affirmative....

The next step was to invite Wulf to dine with him, to show him the waistcoat and prove beyond doubt that it had been made by a tailor of Glotzbourg.

Juve's opinion had now become a solid conviction. FantÔmas had worn the garment, and had carried the diamond in the pocket of the waistcoat he found in the Marquis de SÉrac's apartment. Hence the Marquis de SÉrac was FantÔmas.