M. Desmalions remained thinking for a time and then objected: 

“Still, in the letters which he wrote, M. Fauville accuses his wife.”

“He does.”

“We must therefore admit either that he was right in accusing her or that the letters are forged?”

“They are not forged.  All the experts have recognized M. Fauville’s handwriting.”

“Then?”

“Then—­”

Don Luis did not finish his sentence; and M. Desmalions felt the breath of the truth fluttering still nearer round him.

The others, one and all as anxious as himself, were silent.  He muttered: 

“I do not understand—­”

“Yes, Monsieur le Prefet, you do.  You understand that, if the sending of those letters forms an integrate part of the plot hatched against Mme. Fauville and Gaston Sauverand, it is because their contents were prepared in such a way as to be the undoing of the victims.”

“What!  What!  What are you saying?”

“I am saying what I said before.  Once they are innocent, everything that tells against them is part of the plot.”

Again there was a long silence.  The Prefect of Police did not conceal his agitation.  Speaking very slowly, with his eyes fixed on Don Luis’s eyes, he said: 

“Whoever the culprit may be, I know nothing more terrible than this work of hatred.”

“It is an even more improbable work than you can imagine, Monsieur le Prefet,” said Perenna, with growing animation, “and it is a hatred of which you, who do not know Sauverand’s confession, cannot yet estimate the violence.  I understood it completely as I listened to the man; and, since then, all my thoughts have been overpowered by the dominant idea of that hatred.  Who could hate like that?  To whose loathing had Marie Fauville and Sauverand been sacrificed?  Who was the inconceivable person whose perverted genius had surrounded his two victims with chains so powerfully forged?

“And another idea came to my mind, an earlier idea which had already struck me several times and to which I have already referred in Sergeant Mazeroux’s presence:  I mean the really mathematical character of the appearance of the letters.  I said to myself that such grave documents could not be introduced into the case at fixed dates unless some primary reason demanded that those dates should absolutely be fixed.  What reason?  If a human agency had been at work each time, there would surely have been some irregularity dependent on this especially after the police had become cognizant of the matter and were present at the delivery of the letters.