Daubrecq burst into a great roar of laughter:

"Lord, how funny! Forty thousand francs! You've paid forty thousand francs! To M. Nicole, I suppose, who sold you the list of the Twenty-seven? Well, would you like me to tell you the real name of M. Nicole? It's Arsene Lupin!"

"I know that."

"Very likely. But what you don't know, you silly ass, is that I have come straight from Stanislas Vorenglade's and that Stanislas Vorenglade left Paris four days ago! Oh, what a joke! They've sold you waste paper! And your forty thousand francs! What an ass! What an ass!"

He walked out of the room, screaming with laughter and leaving Prasville absolutely dumbfounded.

So Arsene Lupin possessed no proof at all; and, when he was threatening and commanding and treating Prasvile with that airy insolence, it was all a farce, all bluff!

"No, no, it's impossible," thought the secretary-general. "I have the sealed envelope. ... It's here. ... I have only to open it."

He dared not open it. He handled it, weighed it, examined it... And doubt made its way so swiftly into his mind that he was not in the least surprised, when he did open it, to find that it contained four blank sheets of note-paper.

"Well, well," he said, "I am no match for those rascals. But all is not over yet."

And, in point of fact, all was not over. If Lupin had acted so daringly, it showed that the letters existed and that he relied upon buying them from Stanislas Vorenglade. But, as, on the other hand, Vorenglade was not in Paris, Prasville's business was simply to forestall Lupin's steps with regard to Vorenglade and obtain the restitution of those dangerous letters from Vorenglade at all costs. The first to arrive would be the victor.

Prasville once more took his hat, coat and stick, went downstairs, stepped into a taxi and drove to Vorenglade's flat.

Here he was told that the ex-deputy was expected home from London at six o'clock that evening.

It was two o'clock in the afternoon. Prasville therefore had plenty of time to prepare his plan.

He arrived at the Gare du Nord at five o'clock and posted all around, in the waiting-rooms and in the railway-offices, the three or four dozen detectives whom he had brought with him.

This made him feel easy. If M. Nicole tried to speak to Vorenglade, they would arrest Lupin. And, to make assurance doubly sure, they would arrest whosoever could be suspected of being either Lupin or one of Lupin's emissaries.

Moreover, Prasville made a close inspection of the whole station. He discovered nothing suspicious. But, at ten minutes to six, Chief-inspector Blanchon, who was with him, said:

"Look, there's Daubrecq."

Daubrecq it was; and the sight of his enemy exasperated the secretary-general to such a pitch that he was on the verge of having him arrested. But he reflected that he had no excuse, no right, no warrant for the arrest.

Besides, Daubrecq's presence proved, with still greater force, that everything now depended on Stanislas Vorenglade. Vorenglade possessed the letters: who would end by having them? Daubrecq? Lupin? Or he, Prasville?