Shoveling over the loose dirt along the track, they continued on until the cutting which had so nearly been a grave for Fred was passed, and then Sam said as he halted:
"It's no use to hunt here. It couldn't have got up this way."
"The draught may have carried it quite a distance."
"There isn't air enough stirrin' to move it a foot; but it won't do much harm to look."
They were nearly at the chamber where Sam was taken prisoner before Fred abandoned the hunt, and as he turned to retrace his steps both came to a sudden halt.
As if from beneath their feet arose a muffled cry of distress.
The boys looked at each other in alarm, and as they stood motionless the mysterious sound was repeated.
"What can it mean?" Fred asked in a whisper.
"That's more'n I can tell. There's no drift below this."
"That was surely a human being, and in trouble of some kind."