Fanferlot waited a long time, but did not wax impatient, for he had often had to remain on watch entire days and nights at a time, with much less important objects in view than the present one.  Besides, his mind was busily occupied in estimating the value of his discoveries, weighing his chances, and, like Perrette with her pot of milk, building the foundation of his fortune upon present success.

Finally, about one o’clock, he saw Cavaillon rise from his desk, change his coat, and take down his hat.

“Very good!” he exclaimed, “my man is coming out; I must keep my eyes open.”

The next moment Cavaillon appeared at the door of the bank; but before stepping on the pavement he looked up and down the street in an undecided manner.

“Can he suspect anything?” thought Fanferlot.

No, the young clerk suspected nothing; only having a commission to execute, and fearing his absence would be observed, he was debating with himself which would be the shortest road for him to take.

He soon decided, entered the Faubourg Montmartre, and walked up the Rue Notre Dame de Lorette so rapidly, utterly regardless of the grumbling passers-by whom he elbowed out of his way, that Fanferlot found it difficult to keep him in sight.

Reaching the Rue Chaptal, Cavaillon suddenly stopped, and entered the house numbered 39.

He had scarcely taken three steps in the narrow corridor when he felt a touch on his shoulder, and turning abruptly, found himself face to face with Fanferlot.

He recognized him at once, and turning very pale he shrank back, and looked around for means of escape.

But the detective, anticipating the attempt, barred the passage-way.  Cavaillon saw that he was fairly caught.

“What do you want with me?” he asked in a voice tremulous with fright.

Fanferlot was distinguished among his confreres for his exquisite suavity and unequalled urbanity.  Even with his prisoners he was the perfection of courtesy, and never was known to handcuff a man without first obsequiously apologizing for being compelled to do so.

“You will be kind enough, my dear monsieur,” he said, “to excuse the great liberty I take; but I really am under the necessity of asking you for a little information.”

“Information!  From me, monsieur?”

“From you, my dear monsieur; from M. Eugene Cavaillon.”

“But I do not know you.”

“Ah, yes; you remember seeing me this morning.  It is only about a trifling matter, and you will overwhelm me with obligations if you will do me the honor to accept my arm, and step outside for a moment.”

What could Cavaillon do?  He took Fanferlot’s arm, and went out with him.

The Rue Chaptal is not one of those noisy thoroughfares where foot-passengers are in perpetual danger of being run over by numberless vehicles dashing to and fro; there were but two or three shops, and from the corner of Rue Fontaine occupied by an apothecary, to the entrance of the Rue Leonie, extended a high, gloomy wall, broken here and there by a small window which lighted the carpenters’ shops behind.