"But, I say, look here, it wasn't he who set the place on fire! How do you make out that he set it on fire, seeing that he never left us?"

"Why, he set it on fire beforehand, to be sure!"

"How? I ask you, how?"

"How do I know? But a fire doesn't break out like that, for no reason at all, at the very moment when a man wants to burn compromising papers."

They heard a commotion upstairs. It was the waiters of the restaurant trying to burst the door open. An acrid smell filled the well of the stair-case.

Renine reached the top floor:

"By your leave, friends. I have the key."

He inserted it in the lock and opened the door.

He was met by a gust of smoke so dense that one might well have supposed the whole floor to be ablaze. Renine at once saw that the fire had gone out of its own accord, for lack of fuel, and that there were no more flames:

"M. Morisseau, you won't let any one come in with us, will you? An intruder might spoil everything. Bolt the door, that will be best."

He stepped into the front room, where the fire had obviously had its chief centre. The furniture, the walls and the ceiling, though blackened by the smoke, had not been touched. As a matter of fact, the fire was confined to a blaze of papers which was still burning in the middle of the room, in front of the window.

Renine struck his forehead:

"What a fool I am! What an unspeakable a.s.s!"

"Why?" asked the inspector.

"The hat-box, of course! The cardboard hat-box which was standing on the table. That's where he hid the notes. They were there all through our search."

"Impossible!"

"Why, yes, we always overlook that particular hiding-place, the one just under our eyes, within reach of our hands! How could one imagine that a thief would leave sixty thousand francs in an open cardboard box, in which he places his hat when he comes in, with an absent-minded air? That's just the one place we don't look in.... Well played, M. Dutreuil!"

The inspector, who remained incredulous, repeated:

"No, no, impossible! We were with him and he could not have started the fire himself."

"Everything was prepared beforehand on the supposition that there might be an alarm.... The hat-box ... the tissue paper ... the bank-notes: they must all have been steeped in some inflammable liquid. He must have thrown a match, a chemical preparation or what not into it, as we were leaving."

"But we should have seen him, hang it all! And then is it credible that a man who has committed a murder for the sake of sixty thousand francs should do away with the money in this way? If the hiding-place was such a good one--and it was, because we never discovered it--why this useless destruction?"

"He got frightened, M. Morisseau. Remember that his head is at stake and he knows it. Anything rather than the guillotine; and they--the bank-notes--were the only proof which we had against him. How could he have left them where they were?"

Morisseau was flabbergasted:

"What! The only proof?"

"Why, obviously!"

"But your witnesses? Your evidence? All that you were going to tell the chief?"

"Mere bluff."

"Well, upon my word," growled the bewildered inspector, "you're a cool customer!"

"Would you have taken action without my bluff?"

"No."

"Then what more do you want?"

Renine stooped to stir the ashes. But there was nothing left, not even those remnants of stiff paper which still retain their shape.

"Nothing," he said. "It's queer, all the same! How the deuce did he manage to set the thing alight?"

He stood up, looking attentively about him. Hortense had a feeling that he was making his supreme effort and that, after this last struggle in the dark, he would either have devised his plan of victory or admit that he was beaten.

Faltering with anxiety, she asked:

"It's all up, isn't it?"

"No, no," he said, thoughtfully, "it's not all up. It was, a few seconds ago. But now there is a gleam of light ... and one that gives me hope."

"G.o.d grant that it may be justified!"

"We must go slowly," he said. "It is only an attempt, but a fine, a very fine attempt; and it may succeed."

He was silent for a moment; then, with an amused smile and a click of the tongue, he said:

"An infernally clever fellow, that Dutreuil! His trick of burning the notes: what a fertile imagination! And what coolness! A pretty dance the beggar has led me! He's a master!"

He fetched a broom from the kitchen and swept a part of the ashes into the next room, returning with a hat-box of the same size and appearance as the one which had been burnt. After crumpling the tissue paper with which it was filled, he placed the hat-box on the little table and set fire to it with a match.

It burst into flames, which he extinguished when they had consumed half the cardboard and nearly all the paper. Then he took from an inner pocket of his waistcoat a bundle of bank-notes and selected six, which he burnt almost completely, arranging the remains and hiding the rest of the notes at the bottom of the box, among the ashes and the blackened bits of paper:

"M. Morisseau," he said, when he had done, "I am asking for your a.s.sistance for the last time. Go and fetch Dutreuil. Tell him just this: 'You are unmasked. The notes did not catch fire. Come with me.' And bring him up here."

Despite his hesitation and his fear of exceeding his instructions from the head of the detective service, the chief-inspector was powerless to throw off the ascendancy which Renine had acquired over him. He left the room.

Renine turned to Hortense:

"Do you understand my plan of battle?"

"Yes," she said, "but it's a dangerous experiment. Do you think that Dutreuil will fall into the trap?"

"Everything depends on the state of his nerves and the degree of demoralization to which he is reduced. A surprise attack may very well do for him."

"Nevertheless, suppose he recognizes by some sign that the box has been changed?"