"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-cla.s.s 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 to have taken those bricks down carefully, one by one."

Quickly he took brick after brick from the pile, and began to range them neatly against the wall on the left. The Duke watched him for two or three minutes, then began to help him. It did not take them long, and under one of the last few bricks Guerchard found a fragment of a gilded picture-frame.

"Here's where they ought to have done their sweeping," he said, holding it up to the Duke.

"I tell you what," said the Duke, "I shouldn't wonder if we found the furniture in this house still."

"Oh, no, no!" said Guerchard. "I tell you that Lupin would allow for myself or Ganimard being put in charge of the case; and he would know that we should find the opening in the chimney. The furniture was taken straight out into the side-street on to which this house opens." He led the way out of the room on to the landing and went down the dark staircase into the hall. He opened the shutters of the hall windows, and let in the light. Then he examined the hall. The dust lay thick on the tiled floor. Down the middle of it was a lane formed by many feet.

The footprints were faint, but still plain in the layer of dust.

Guerchard came back to the stairs and began to examine them. Half-way up the flight he stooped, and picked up a little spray of flowers: "Fresh!" he said. "These have not been long plucked."

"Salvias," said the Duke.

"Salvias they are," said Guerchard. "Pink salvias; and there is only one gardener in France who has ever succeeded in getting this shade--M.

Gournay-Martin's gardener at Charmerace. I'm a gardener myself."

"Well, then, last night's burglars came from Charmerace. They must have," said the Duke.

"It looks like it," said Guerchard.

"The Charolais," said the Duke.

"It looks like it," said Guerchard.

"It must be," said the Duke. "This IS interesting--if only we could get an absolute proof."

"We shall get one presently," said Guerchard confidently.

"It is interesting," said the Duke in a tone of lively enthusiasm.

"These clues--these tracks which cross one another--each fact by degrees falling into its proper place--extraordinarily interesting." He paused and took out his cigarette-case: "Will you have a cigarette?" he said.

"Are they caporal?" said Guerchard.

"No, Egyptians--Mercedes."

"Thank you," said Guerchard; and he took one.

The Duke struck a match, lighted Guerchard's cigarette, and then his own:

"Yes, it's very interesting," he said. "In the last quarter of an hour you've practically discovered that the burglars came from Charmerace--that they were the Charolais--that they came in by the front door of this house, and carried the furniture out of it."

"I don't know about their coming in by it," said Guerchard. "Unless I'm very much mistaken, they came in by the front door of M.

Gournay-Martin's house."

"Of course," said the Duke. "I was forgetting. They brought the keys from Charmerace."

"Yes, but who drew the bolts for them?" said Guerchard. "The concierge bolted them before he went to bed. He told me so. He was telling the truth--I know when that kind of man is telling the truth."

"By Jove!" said the Duke softly. "You mean that they had an accomplice?"

"I think we shall find that they had an accomplice. But your Grace is beginning to draw inferences with uncommon quickness. I believe that you would make a first-cla.s.s detective yourself--with practice, of course--with practice."

"Can I have missed my true career?" said the Duke, smiling. "It's certainly a very interesting game."

"Well, I'm not going to search this barracks myself," said Guerchard.

"I'll send in a couple of men to do it; but I'll just take a look at the steps myself."

So saying, he opened the front door and went out and examined the steps carefully.

"We shall have to go back the way we came," he said, when he had finished his examination. "The drawing-room door is locked. We ought to find M. Formery hammering on it." And he smiled as if he found the thought pleasing.

They went back up the stairs, through the opening, into the drawing-room of M. Gournay-Martin's house. Sure enough, from the other side of the locked door came the excited voice of M. Formery, crying:

"Guerchard! Guerchard! What are you doing? Let me in! Why don't you let me in?"

Guerchard unlocked the door; and in bounced M. Formery, very excited, very red in the face.

"Hang it all, Guerchard! What on earth have you been doing?" he cried.

"Why didn't you open the door when I knocked?"

"I didn't hear you," said Guerchard. "I wasn't in the room."

"Then where on earth have you been?" cried M. Formery.

Guerchard looked at him with a faint, ironical smile, and said in his gentle voice, "I was following the real track of the burglars."

CHAPTER XV

THE EXAMINATION OF SONIA

M. Formery gasped: "The real track?" he muttered.

"Let me show you," said Guerchard. And he led him to the fireplace, and showed him the opening between the two houses.