The police, assured from this moment of victory and having nearly all the actors in the tragedy in their power, had gradually given way to indiscretion; and, thanks to the particulars revealed to this or that journalist, the public knew of Don Luis’s change of attitude, suspected his passion for Florence Levasseur and the real cause of his right-about-face, and thrilled with excitement as they saw that astonishing figure enter upon a fresh struggle.

What was he going to do?  If he wanted to save the woman he loved from prosecution and to release Marie and Sauverand from prison, he would have to intervene some time that night, to take part, somehow or other, in the event at hand, and to prove the innocence of the three accomplices, either by arresting the invisible bearer of the fourth letter or by suggesting some plausible explanation.  In short, he would have to be there; and that was interesting indeed!

And then the news of Marie Fauville was not good.  With unwavering obstinacy she persisted in her suicidal plans.  She had to be artificially fed; and the doctors in the infirmary at Saint-Lazare did not conceal their anxiety.  Would Don Luis Perenna arrive in time?

Lastly, there was that one other thing, the threat of an explosion which was to blow up Hippolyte Fauville’s house ten days after the delivery of the fourth letter, a really impressive threat when it was remembered that the enemy had never announced anything that did not take place at the stated hour.  And, although it was still ten days—­at least, so people thought—­from the date fixed for the catastrophe, the threat made the whole business look more and more sinister.

That evening, therefore, a great crowd made its way, through La Muette and Auteuil, to the Boulevard Suchet, a crowd coming not only from Paris, but also from the suburbs and the provinces.  The spectacle was exciting, and people wanted to see.

They saw only from a distance, for the police had barred the approaches a hundred yards from either side of the house and were driving into the ditches of the fortifications all those who managed to climb the opposite slope.

The sky was stormy, with heavy clouds revealed at intervals by the light of a silver moon.  There were lightning-flashes and peals of distant thunder.  Men sang.  Street-boys imitated the noises of animals.  People formed themselves into groups on the benches and pavements and ate and drank while discussing the matter.

A part of the night was spent in this way and nothing happened to reward the patience of the crowd, who began to wonder, somewhat wearily, if they would not do better to go home, seeing that Sauverand was in prison and that there was every chance that the fourth letter would not appear in the same mysterious way as the others.

And yet they did not go:  Don Luis Perenna was due to come!

From ten o’clock in the evening the Prefect of Police and his secretary general, the chief detective and Weber, his deputy, Sergeant Mazeroux, and two detectives were gathered in the large room in which Fauville had been murdered.  Fifteen more detectives occupied the remaining rooms, while some twenty others watched the roofs, the outside of the house, and the garden.