This time, he boldly lit the lamp on the table and with it in his hand approached the wall on the right and began to hunt for the spring of the secret opening. He was not long in finding it; a tiny disc, the same colour as the wall and only revealed by its thread-like edge, showed itself to the light of the lamp. He pressed on it, the door of the _cache_ flew open, and in a moment the dagger was in his hand. There was nothing else in the _cache_. Already he had formulated a plan in his mind, a plan which at first sight might seem diabolical, but which he considered, and with justice, the only means with which to meet the case. Camus was no ordinary villain. This room was evidently his stronghold and the _cache_ was evidently his most secret hiding-place. Yet there were no incriminating papers to be found in the room, no papers whatever; nor in the _cache_. This gentleman evidently kept his secrets in his soul. He made no mistakes. Justice, Lavenne felt, might search for ever without finding a tittle of evidence against him, and indeed this fact, de Sartines, who had long known his proclivities, had proved to the hilt. But there is such a thing as Retribution, and in the name of Retribution Lavenne had declared in his own mind that the knife of Camus should be Camus’ undoing. Lavenne, replacing the lamp on the table, examined the dagger minutely without drawing the blade. The design was different on the two sides of the sheath. On one side a fawn trod boldly on jewelled grapes, on the other a serpent of six curves extended itself from the blade-entrance to the point. The pommel on both its sides was of the same design. Nothing could be more striking than the difference between the two sides of this dagger-sheath. One could have told them one from the other in the dark and just by the sense of touch. Lavenne verified this fact with a grim pursing of his lips. The dagger and sheath had been constructed for a set purpose, so that the poisoner who had poisoned one side of the blade might know at once, and before drawing it from its sheath, which was the lethal side. A mistake on this point would have meant death to the poisoner instead of the intended victim. Now Lavenne did not know which side of the blade Camus had poisoned, for the sheath had been covered by the Count’s hand when he put the blade back in it. Lavenne, however, did not in the least require to know which was the poisoned side, or whether it faced to the serpent or the fawn. Camus knew this and that was sufficient. To destroy Camus, Lavenne had only to draw the double-edged blade from the sheath and insert it again, the other way about. That being done, this presenter of fruit to ladies would, when he cut his apple or pear in two, present himself with the poisoned half.