"Listen, Alexandre, and profit by my words. Remember this: when a person is choosing initials for his address at a _poste restante_ he doesn't pick them at random, but always in such a way that the letters convey a meaning to the person corresponding with him, a meaning which will enable that other person easily to remember the address."

"And in this case?"

"In this case, Mazeroux, a man like myself, who knows Neuilly and the neighbourhood of the Bois, is at once struck by those three letters, 'B.R.W,' and especially by the 'W.', a foreign letter, an English letter.

So that in my mind's eye, instantly, as in a flash, I saw the three letters in their logical place as initials at the head of the words for which they stand. I saw the 'B' of 'boulevard,' and the 'R' and the English 'W' of Richard-Wallace. And so I came to the Boulevard Richard-Wallace, And that, my dear sir, explains the milk in the cocoanut."

Mazeroux seemed a little doubtful.

"And what do you think, Chief?"

"I think nothing. I am looking about. I am building up a theory on the first basis that offers a probable theory. And I say to myself ... I say to myself ... I say to myself, Mazeroux, that this is a devilish mysterious little hole and that this house--Hush! Listen--"

He pushed Mazeroux into a dark corner. They had heard a noise, the slamming of a door.

Footsteps crossed the courtyard in front of the house. The lock of the outer gate grated. Some one appeared, and the light of a street lamp fell full on his face.

"Dash it all," muttered Mazeroux, "it's he!"

"I believe you're right."

"It's he. Chief. Look at the black stick and the bright handle. And did you see the eyegla.s.ses--and the beard? What a oner you are, Chief!"

"Calm yourself and let's go after him."

The man had crossed the Boulevard Richard-Wallace and was turning into the Boulevard Maillot. He was walking pretty fast, with his head up, gayly twirling his stick. He lit a cigarette.

At the end of the Boulevard Maillot, the man pa.s.sed the octroi and entered Paris. The railway station of the outer circle was close by. He went to it and, still followed by the others, stepped into a train that took them to Auteuil.

"That's funny," said Mazeroux. "He's doing exactly what he did a fortnight ago. This is where he was seen."

The man now went along the fortifications. In a quarter of an hour he reached the Boulevard Suchet and almost immediately afterward the house in which M. Fauville and his son had been murdered.

He climbed the fortifications opposite the house and stayed there for some minutes, motionless, with his face to the front of the house. Then continuing his road he went to La Muette and plunged into the dusk of the Bois de Boulogne.

"To work and boldly!" said Don Luis, quickening his pace.

Mazeroux stopped him.

"What do you mean, Chief?"

"Well, catch him by the throat! There are two of us; we couldn't hope for a better moment."

"What! Why, it's impossible!"

"Impossible? Are you afraid? Very well, I'll do it by myself."

"Look here, Chief, you're not serious!"

"Why shouldn't I be serious?"

"Because one can't arrest a man without a reason."

"Without a reason? A scoundrel like this? A murderer? What more do you want?"

"In the absence of compulsion, of catching him in the act, I want something that I haven't got."

"What's that?"

"A warrant. I haven't a warrant."

Mazeroux's accent was so full of conviction, and the answer struck Don Luis Perenna as so comical, that he burst out laughing.

"You have no warrant? Poor little chap! Well, I'll soon show you if I need a warrant!"

"You'll show me nothing," cried Mazeroux, hanging on to his companion's arm. "You shan't touch the man."

"One would think he was your mother!"

"Come, Chief."

"But, you stick-in-the-mud of an honest man," shouted Don Luis, angrily, "if we let this opportunity slip shall we ever find another?"

"Easily. He's going home. I'll inform the commissary of police. He will telephone to headquarters; and to-morrow morning--"

"And suppose the bird has flown?"

"I have no warrant."

"Do you want me to sign you one, idiot?"

But Don Luis mastered his rage. He felt that all his arguments would be shattered to pieces against the sergeant's obstinacy, and that, if necessary, Mazeroux would go to the length of defending the enemy against him. He simply said in a sententious tone:

"One a.s.s and you make a pair of a.s.ses; and there are as many a.s.ses as there are people who try to do police work with bits of paper, signatures, warrants, and other gammon. Police work, my lad, is done with one's fists. When you come upon the enemy, hit him. Otherwise, you stand a chance of hitting the air. With that, good-night. I'm going to bed.

Telephone to me when the job is done."

He went home, furious, sick of an adventure in which he had not had elbow room, and in which he had had to submit to the will, or, rather, to the weakness of others.

But next morning when he woke up his longing to see the police lay hold of the man with the ebony stick, and especially the feeling that his a.s.sistance would be of use, impelled him to dress as quickly as he could.

"If I don't come to the rescue," he thought, "they'll let themselves be done in the eye. They're not equal to a contest of this kind."

Just then Mazeroux rang up and asked to speak to him. He rushed to a little telephone box which his predecessor had fitted up on the first floor, in a dark recess that communicated only with his study, and switched on the electric light.

"Is that you, Alexandre?"

"Yes, Chief. I'm speaking from a wine shop near the house on the Boulevard Richard-Wallace."

"What about our man?"