Her look of perfect trust came to him with a stab of pain.

“My poor child,” he muttered, peering about him, “I’m afraid we are—­in trouble—­but—­wait a minute.”

Taking the candle, Coquenil went through the arched opening into the larger chamber and made a hurried inspection.  The room was about fifteen feet square and ten feet high, with everything of stone—­walls, floor, and arched ceiling.  Save for the passage into the smaller room, there was no sign of an opening anywhere except two small square holes near the ceiling, probably ventilating shafts.

[Illustration: 

A. Bag of shavings where Coquenil recovered consciousness in large underground chamber.

B. Table and two chairs in smaller chamber where de Heidelmann-Bruck was writing.

C C C C C C. Logs of wood piled around walls of two chambers.

D. Heavy iron door through which Alice was brought in.

E. Stone shelf above wood pile.

F. F. Opening through thick wall separating chambers, where Coquenil built a barricade of logs.  Dotted lines 1-2, indicate curve of archway.

S. S. Section of wood pile torn down by Alice to make barricade.

X. The second barricade of logs.]

Around the four walls were logs piled evenly to the height of nearly six feet, and at the archway the pile ran straight through into the smaller room.  The logs were in two-foot lengths, and as the archway was about four feet wide, the passage between the two rooms was half blocked with wood.

Coquenil walked slowly around the chamber, peering carefully into cracks between the logs, as if searching for something.  As he went on he held the candle lower and lower, and presently got down upon his hands and knees and crept along the base of the pile.

“What are you doing?” asked Alice, watching him in wonder from the archway.

Without replying, the detective rose to his feet, and holding the candle high above his head, examined the walls above the wood pile.  Then he reached up and scraped the stones with his finger nails in several places, and then held his fingers close to the candlelight and looked at them and smelled them.  His fingers were black with soot.

“M.  Paul, won’t you speak to me?” begged the girl.

“Just a minute, just a minute,” he answered absently.  Then he spoke with quick decision:  “I’m going to set you to work,” he said.  “By the way, have you any idea where we are?”

She looked at him in surprise.  “Why, don’t you know?”

“I think we are on the Rue de Varennes—­a big hotel back of the high wall?”

“That’s right,” she said.

“Ah, he didn’t take me away!” reflected M. Paul.  “That is something.  Pougeot will scent danger and will move heaven and earth to save us.  He will get Tignol and Tignol knows I was here.  But can they find us?  Can they find us?  Tell me, did you come down many stairs?”