This excellent bloodhound had not lost sight of the cashier.  He said to himself, “Now that my young gentleman believes himself to be alone, his face will betray him.  I shall detect a smile or a wink that will enlighten me.”

Leaving M. Fauvel and the commissary to pursue their investigations, he posted himself to watch.  He saw the door open, and Madeleine appear upon the threshold; he lost not a single word or gesture of the rapid scene which had passed.

It mattered little that every word of this scene was an enigma.  M. Fanferlot was skilful enough to complete the sentences he did not understand.

As yet he only had a suspicion; but a mere suspicion is better than nothing; it is a point to start from.  So prompt was he in building a plan upon the slightest incident that he thought he saw in the past of these people, who were utter strangers to him, glimpses of a domestic drama.

If the commissary of police is a sceptic, the detective has faith; he believes in evil.

“I understand the case now,” said he to himself.  “This man loves the young lady, who is really very pretty; and, as he is quite handsome, I suppose his love is reciprocated.  This love-affair vexes the banker, who, not knowing how to get rid of the importunate lover by fair means, has to resort to foul, and plans this imaginary robbery, which is very ingenious.”

Thus to M. Fanferlot’s mind, the banker had simply robbed himself, and the innocent cashier was the victim of an odious machination.

But this conviction was, at present, of little service to Prosper.

Fanferlot, the ambitious, who had determined to obtain renown in his profession, decided to keep his conjectures to himself.

“I will let the others go their way, and I’ll go mine,” he said.  “When, by dint of close watching and patient investigation I shall have collected proof sufficient to insure certain conviction, I will unmask the scoundrel.”

He was radiant.  He had at last found the crime, so long looked for, which would make him celebrated.  Nothing was wanting, neither the odious circumstances, nor the mystery, nor even the romantic and sentimental element represented by Prosper and Madeleine.

Success seemed difficult, almost impossible; but Fanferlot, the Squirrel, had great confidence in his own genius for investigation.

Meanwhile, the search upstairs completed, M. Fauvel and the commissary returned to the room where Prosper was waiting for them.

The commissary, who had seemed so calm when he first came, now looked grave and perplexed.  The moment for taking a decisive part had come, yet it was evident that he hesitated.

“You see, gentlemen,” he began, “our search has only confirmed our first suspicion.”

M. Fauvel and Prosper bowed assentingly.

“And what do you think, M. Fanferlot?” continued the commissary.

Fanferlot did not answer.