“So at seventeen minutes to twelve at night,” he said, “I fathomed the mystery.”

He tried to control his emotion, but it was too great; and his nerves were so immensely staggered by the trial that he began to shed tears.  He had caught sight of the appalling truth, all of a sudden, as when at night one half sees a landscape under a lightning-flash.

There is nothing more unnerving than this sudden illumination when we have been groping and struggling in the dark.  Already exhausted by his physical efforts and by the want of food, from which he was beginning to suffer, he felt the shock so intensely that, without caring to think a moment longer, he managed to go to sleep, or, rather, to sink into sleep, as one sinks into the healing waters of a bath.

When he woke, in the small hours, alert and well despite the discomfort of his couch, he shuddered on thinking of the theory which he had accepted; and his first instinct was to doubt it.  He had, so to speak, no time.

All the proofs came rushing to his mind of their own accord and at once transformed the theory into one of those certainties which it would be madness to deny.  It was that and nothing else.  As he had foreseen, the truth lay recorded in Sauverand’s story.  And he had not been mistaken, either, in saying to Mazeroux that the manner in which the mysterious letters appeared had put him on the track of the truth.

And the truth was terrible.  He felt, at the thought of it, the same fears that had maddened Inspector Verot when, already tortured by the poison, he stammered: 

“Oh, I don’t like this, I don’t like the look of this!...  The whole thing has been planned in such an infernal manner!”

Infernal was the word!  And Don Luis remained stupefied at the revelation of a crime which looked as if no human brain could have conceived it.

For two hours more he devoted all his mental powers to examining the situation from every point of view.  He was not much disturbed about the result, because, being now in possession of the terrible secret, he had nothing more to do but make his escape and go that evening to the meeting on the Boulevard Suchet, where he would show them all how the murder was committed.

But when, wishing to try his chance of escaping, he went up through the underground passage and climbed to the top of the upper ladder—­that is to say, to the level of the boudoir—­he heard through the trapdoor the voices of men in the room.

“By Jove!” he said to himself, “the thing is not so simple as I thought!  In order to escape the minions of the law I must first leave my prison; and here is at least one of the exits blocked.  Let’s look at the other.”

He went down to Florence’s apartments and worked the mechanism, which consisted of a counterweight.  The panel of the cupboard moved in the groove.

Driven by horror and hoping to find some provisions which enable him to withstand a siege without being reduced to famine, he was about to pass through the alcove, behind the curtains, when he was stopped short by a sound of footsteps.  Some one had entered the room.