Hippolyte Fauville shook his head.

"No, no, it would be useless, for the moment.... My proofs would not be sufficient.... No, really not."

He had already risen from his chair and stood apologizing:

"Monsieur le Prefet, I have disturbed you unnecessarily, but I wanted to know.... I was hoping that Inspector Verot might have escaped.... His evidence, joined to mine, would have been invaluable. But perhaps he was able to tell you?"

"No, he spoke of this evening--of to-night--"

Hippolyte Fauville started.

"This evening! Then the time has come!... But no, it's impossible, they can't do anything to me yet.... They are not ready--"

"Inspector Verot declared, however, that the double murder would be committed to-night."

"No, Monsieur le Prefet, he was wrong there.... I know all about it.... To-morrow evening at the earliest ... and we will catch them in a trap.... Oh, the scoundrels!"

Don Luis went up to him and asked:

"Your mother's name was Ermeline Roussel, was it not?"

"Yes, Ermeline Roussel. She is dead now."

"And she was from Saint-Etienne?"

"Yes. But why these questions?"

"Monsieur le Prefet will tell you to-morrow. One word more." He opened the cardboard box left by Inspector Verot. "Does this cake of chocolate mean anything to you? These marks?"

"Oh, how awful!" said the civil engineer, in a hoa.r.s.e tone. "Where did the inspector find it?"

He dropped into his chair again, but only for a moment; then, drawing himself up, he hurried toward the door with a jerky step.

"I'm going, Monsieur le Prefet, I'm going. To-morrow morning I'll show you.... I shall have all the proofs.... And the police will protect me.... I am ill, I know, but I want to live! I have the right to live ... and my son, too.... And we will live.... Oh, the scoundrels!--"

And he ran, stumbling out, like a drunken man.

M. Desmalions rose hastily.

"I shall have inquiries made about that man's circ.u.mstances.... I shall have his house watched. I've telephoned to the detective office already.

I'm expecting some one in whom I have every confidence."

Don Luis said:

"Monsieur le Prefet, I beg you, with an earnestness which you will understand, to authorize me to pursue the investigation. Cosmo Mornington's will makes it my duty and, allow me to say, gives me the right to do so. M. Fauville's enemies have given proofs of extraordinary cleverness and daring. I want to have the honour of being at the post of danger to-night, at M. Fauville's house, near his person."

The Prefect hesitated. He was bound to reflect how greatly to Don Luis Perenna's interest it was that none of the Mornington heirs should be discovered, or at least be able to come between him and the millions of the inheritance. Was it safe to attribute to a n.o.ble sentiment of grat.i.tude, to a lofty conception of friendship and duty, that strange longing to protect Hippolyte Fauville against the death that threatened him?

For some seconds M. Desmalions watched that resolute face, those intelligent eyes, at once innocent and satirical, grave and smiling, eyes through which you could certainly not penetrate their owner's baffling individuality, but which nevertheless looked at you with an expression of absolute frankness and sincerity. Then he called his secretary:

"Has any one come from the detective office?"

"Yes, Monsieur le Prefet; Sergeant Mazeroux is here."

"Please have him shown in."

And, turning to Perenna:

"Sergeant Mazeroux is one of our smartest detectives. I used to employ him together with that poor Verot when I wanted any one more than ordinarily active and sharp. He will be of great use to you."

Sergeant Mazeroux entered. He was a short, lean, wiry man, whose drooping moustache, heavy eyelids, watery eyes and long, lank hair gave him a most doleful appearance.

"Mazeroux," said the Prefect, "you will have heard, by this time, of your comrade Verot's death and of the horrible circ.u.mstances attending it. We must now avenge him and prevent further crimes. This gentleman, who knows the case from end to end, will explain all that is necessary. You will work with him and report to me to-morrow morning."

This meant giving a free hand to Don Luis Perenna and relying on his power of initiative and his perspicacity. Don Luis bowed:

"I thank you, Monsieur le Prefet. I hope that you will have no reason to regret the trust which you are good enough to place in me."

And, taking leave of M. Desmalions and Maitre Lepertuis, he went out with Sergeant Mazeroux.

As soon as they were outside, he told Mazeroux what he knew. The detective seemed much impressed by his companion's professional gifts and quite ready to be guided by his views.

They decided first to go to the Cafe du Pont-Neuf. Here they learned that Inspector Verot, who was a regular customer of the place, had written a long letter there that morning. And the waiter remembered that a man at the next table, who had entered the cafe at almost the same time as the inspector, had also asked for writing-paper and called twice for yellow envelopes.

"That's it," said Mazeroux to Don Luis. "As you suspected, one letter has been subst.i.tuted for the other."

The description given by the waiter was pretty explicit: a tall man, with a slight stoop, wearing a reddish-brown beard cut into a point, a tortoise-sh.e.l.l eyegla.s.s with a black silk ribbon, and an ebony walking-stick with a handle shaped like a swan's head.

"That's something for the police to go upon," said Mazeroux.

They were leaving the cafe when Don Luis stopped his companion.

"One moment."

"What's the matter?"

"We've been followed."

"Followed? What next? And by whom, pray?"

"No one that matters. I know who it is and I may as well settle his business and have done with it. Wait for me. I shall be back; and I'll show you some fun. You shall see one of the 'nuts,' I promise you."

He returned in a minute with a tall, thin man with his face set in whiskers. He introduced him:

"M. Mazeroux, a friend of mine, Senor Caceres, an attache at the Peruvian Legation. Senor Caceres took part in the interview at the Prefect's just now. It was he who, on the Peruvian Minister's instructions, collected the doc.u.ments bearing upon my ident.i.ty." And he added gayly: "So you were looking for me, dear Senor Caceres. Indeed, I expected, when we left the police office--"

The Peruvian attache made a sign and pointed to Sergeant Mazeroux.