which lifted for but a brief space at the appearance of a fresh delicacy. Guerchard ate and drank seriously, answering the questions of the Duke in a somewhat absent-minded fashion. The Duke himself seemed to have lost his usual flow of good spirits, and at times his brow was knitted in an anxious frown. His questions to Guerchard showed a far less keen interest in the affair.
To him the lunch seemed very long and very tedious; but at last it came to an end. M. Gournay-Martin seemed to have been much cheered by the wine he had drunk. He was almost hopeful. M. Formery, who had not by any means trifled with the champagne, was raised to the very height of sanguine certainty. Their coffee and liqueurs were served in the smoking-room. Guerchard lighted a cigar, refused a liqueur, drank his coffee quickly, and slipped out of the room.
The Duke followed him, and in the hall said: "I will continue to watch you unravel the threads of this mystery, if I may, M. Guerchard."
Good Republican as Guerchard was, he could not help feeling flattered by the interest of a Duke; and the excellent lunch he had eaten disposed him to feel the honour even more deeply.
"I shall be charmed," he said. "To tell the truth, I find the company of your Grace really quite stimulating."
"It must be because I find it all so extremely interesting," said the Duke.
They went up to the drawing-room and found the red-faced young policeman seated on a chair by the door eating a lunch, which had been sent up to him from the millionaire's kitchen, with a very hearty appetite.
They went into the drawing-room. Guerchard shut the door and turned the key: "Now," he said, "I think that M. Formery will give me half an hour to myself. His cigar ought to last him at least half an hour. In that time I shall know what the burglars really did with their plunder—at least I shall know for certain how they got it out of the house."
"Please explain," said the Duke. "I thought we knew how they got it out of the house." And he waved his hand towards the window.
"Oh, that!—that's childish," said Guerchard contemptuously. "Those are traces for an examining magistrate. The ladder, the table on the window-sill, they lead nowhere. The only people who came up that ladder were the two men who brought it from the scaffolding. You can see their footsteps. Nobody went down it at all. It was mere waste of time to bother with those traces."
"But the footprint under the book?" said the Duke.
"Oh, that," said Guerchard. "One of the burglars sat on the couch there, rubbed plaster on the sole of his boot, and set his foot down on the carpet. Then he dusted the rest of the plaster off his boot and put the book on the top of the footprint."
"Now, how do you know that?" said the astonished Duke.
"It's as plain as a pike-staff," said Guerchard. "There must have been several burglars to move such pieces of furniture. If the soles of all of them had been covered with plaster, all the sweeping in the world would not have cleared the carpet of the tiny fragments of it. I've been over the carpet between the footprint and the window with a magnifying glass. There are no fragments of plaster on it. We dismiss the footprint. It is a mere blind, and a very fair blind too—for an examining magistrate."
"I understand," said the Duke.
"That narrows the problem, the quite simple problem, how was the furniture taken out of the room. It did not go through that window down the ladder. Again, it was not taken down the stairs, and out of the front door, or the back. If it had been, the concierge and his wife would have heard the noise. Besides that, it would have been carried down into a main street, in which there are people at all hours. Somebody would have been sure to tell a policeman that this house was being emptied. Moreover, the police were continually patrolling the main streets, and, quickly as a man like Lupin would do the job, he could not do it so quickly that a policeman would not have seen it. No; the furniture was not taken down the stairs or out of the front door. That narrows the problem still more. In fact, there is only one mode of egress left."
"The chimney!" cried the Duke.
"You've hit it," said Guerchard, with a husky laugh. "By that well-known logical process, the process of elimination, we've excluded all methods of egress except the chimney."
He paused, frowning, in some perplexity; and then he said uneasily: "What I don't like about it is that Victoire was set in the fireplace. I asked myself at once what was she doing there. It was unnecessary that she should be drugged and set in the fireplace—quite unnecessary."
"It might have been to put off an examining magistrate," said the Duke. "Having found Victoire in the fireplace, M. Formery did not look for anything else."
"Yes, it might have been that," said Guerchard slowly. "On the other hand, she might have been put there to make sure that I did not miss the road the burglars took. That's the worst of having to do with Lupin. He knows me to the bottom of my mind. He has something up his sleeve—some surprise for me. Even now, I'm nowhere near the bottom of the mystery. But come along, we'll take the road the burglars took. The inspector has put my lantern ready for me."
As he spoke he went to the fireplace, picked up a lantern which had been set on the top of the iron fire-basket, and lighted it. The Duke stepped into the great fireplace beside him. It was four feet deep, and between eight and nine feet broad. Guerchard threw the light from the lantern on to the back wall of it. Six feet from the floor the soot from the fire stopped abruptly, and there was a dappled patch of bricks, half of them clean and red, half of them blackened by soot, five feet broad, and four feet high.
"The opening is higher up than I thought," said Guerchard. "I must get a pair of steps."
He went to the door of the drawing-room and bade the young policeman fetch him a pair of steps. They were brought quickly. He took them from the policeman, shut the door, and locked it again. He set the steps in the fireplace and mounted them.
"Be careful," he said to the Duke, who had followed him into the fireplace, and stood at the foot of the steps. "Some of these bricks may drop inside, and they'll sting you up if they fall on your toes."
The Duke stepped back out of reach of any bricks that might fall.
Guerchard set his left hand against the wall of the chimney-piece between him and the drawing-room, and pressed hard with his right against the top of the dappled patch of bricks. At the first push, half a dozen of them fell with a bang on to the floor of the next house. The light came flooding in through the hole, and shone on Guerchard's face and its smile of satisfaction. Quickly he pushed row after row of bricks into the next house until he had cleared an opening four feet square.
"Come along," he said to the Duke, and disappeared feet foremost through the opening.
The Duke mounted the steps, and found himself looking into a large empty room of the exact size and shape of the drawing-room of M. Gournay-Martin, save that it had an ordinary modern fireplace instead of one of the antique pattern of that in which he stood. Its chimney-piece was a few inches below the opening. He stepped out on to the chimney-piece and dropped lightly to the floor.
"Well," he said, looking back at the opening through which he had come. "That's an ingenious dodge."
"Oh, it's common enough," said Guerchard. "Robberies at the big jewellers' are sometimes worked by these means. But what is uncommon about it, and what at first sight put me off the track, is that these burglars had the cheek to pierce the wall with an opening large enough to enable them to remove the furniture of a house."
"It's true," said the Duke. "The opening's as large as a good-sized window. Those burglars seem capable of everything—even of a first-class piece of mason's work."
"Oh, this has all been prepared a long while ago. But now I'm really on their track. And after all, I haven't really lost any time. Dieusy wasted no time in making inquiries in Sureau Street; he's been working all this side of the house."
Guerchard drew up the blinds, opened the shutters, and let the daylight flood the dim room. He came back to the fireplace and looked down at the heap of bricks, frowning:
"I made a mistake there," he said. "I ought