“Do you begin to understand now?” asked M. Lecoq.

“Understand, patron?  Why, a child could understand it now.  Ah, what a man you are!  I see the scene as if I had been present.  Two persons were present at the robbery; one wished to take the money, the other wished to prevent its being taken.  That is clear, that is certain.”

Accustomed to triumphs of this sort, M. Lecoq was much amused at Fanferlot’s enthusiasm.

“There you go off, half-primed again,” he said, good-humoredly:  “you regard as sure proof a circumstance which may be accidental, and at the most only probable.”

“No, patron, no! a man like you could not be mistaken:  doubt no longer exists.”

“That being the case, what deductions would you draw from our discovery?”

“In the first place, it proves that I am correct in thinking the cashier innocent.”

“How so?”

“Because, at perfect liberty to open the safe whenever he wished to do so, it is not likely that he would have brought a witness when he intended to commit the theft.”

“Well reasoned, Fanferlot.  But on this supposition the banker would be equally innocent:  reflect a little.”

Fanferlot reflected, and all of his animation vanished.

“You are right,” he said in a despairing tone.  “What can be done now?”

“Look for the third rogue, or rather the real rogue, the one who opened the safe, and stole the notes, and who is still at large, while others are suspected.”

“Impossible, patron—­impossible!  Don’t you know that M. Fauvel and his cashier had keys, and they only?  And they always kept these keys in their pockets.”

“On the evening of the robbery the banker left his key in the secretary.”

“Yes; but the key alone was not sufficient to open the safe; the word also must be known.”

M. Lecoq shrugged his shoulders impatiently.

“What was the word?” he asked.

“Gypsy.”

“Which is the name of the cashier’s grisette.  Now keep your eyes open.  The day you find a man sufficiently intimate with Prosper to be aware of all the circumstances connected with this name, and at the same time on a footing with the Fauvel family which would give him the privilege of entering M. Fauvel’s chamber, then, and not until then, will you discover the guilty party.  On that day the problem will be solved.”

Self-sufficient and vain, like all famous men, M. Lecoq had never had a pupil, and never wished to have one.  He worked alone, because he hated assistants, wishing to share neither the pleasures of success nor the pain of defeat.

Thus Fanferlot, who knew his patron’s character, was surprised to hear him giving advice, who heretofore had only given orders.

He was so puzzled, that in spite of his pre-occupation he could not help betraying his surprise.

“Patron,” he ventured to say, “you seem to take a great interest in this affair, you have so deeply studied it.”