“I'll see!”
He heard her creeping cautiously along the walls of stone, feeling as she went.
“Look out!” he warned. “Keep testing the floor as you go. There may be a crevice or pit or something of that kind.”
All at once she cried: “Here it is! I've found it!”
“Good! Now, then, feel it all over and see if there's any rough place on it. Any sharp edge of a plate, or anything of that kind, that I could rub the cords on.”
Another silence. Then the girl spoke.
“Nothing of that kind here,” she answered depairingly. “The door's as smooth as if it had been filed and polished. There's not even a lock of any kind. It must be fastened from the outside in some way.”
“By Heaven, this is certainly a hard proposition!” exclaimed the engineer, groaning despite himself. “What the deuce are we going to do now?”
For a moment he remained sunk in a kind of dull and apathetic respair.
But suddenly he gave a cry of joy.