“Yes, it’s the only way out,” agreed Blake, who, now that his cut had been bound up with bandages from the first-aid kits the boys carried, felt better.  “We’ll have to dig out.”  And after a short rest they began this work.

A terrible fear was upon them, a fear greater than that caused by their capture by the Germans with the possibility of being shot as spies.  It was the fear of a horrible death—­buried alive.

They dug as best they could for some time with the broken boards, their hands becoming cut and bruised by the rough edges.  And yet, with all their efforts, they could not see that they had gained much.

They were digging back along the way they had come in, for, as Blake said, they knew how long the tunnel was in that direction, but they did not know how far it extended the other way.

“Is it of any use to continue?” asked Joe wearily, when they had been digging for what seemed several hours, though really it was not as long as that.

“Of course we’ve got to continue!” declared Blake, half savagely.  “We can’t give up now—­and die!”

“We may die anyhow,” said Joe.

They were resting in the darkness after strenuous digging.  In the dark because, to save the battery, they had switched off the electric light by which they had been working.

Charlie turned to look back.  They had been piling the earth behind them as they worked, but there was not much of it as yet.  They had made but small impression on the debris that hemmed them in.  And as Charlie looked he uttered a cry.

“What is it?” asked Blake.

“A light!  Don’t you see a light there?” Charlie demanded.  “See!  Back there through the chinks in the rock.  See, a flickering light!”

There was no doubt of it!  There was a gleam of light, and it appeared to come from a point where some fallen rocks were loosely piled.

Dropping their boards, which they had been using for shovels, the boys climbed as near as they could to the hole.  In the dark as they were, the light showed plainly.

“Can you see anything?” asked Charlie of Joe, who was nearest.

“No, only some figures moving about.  It seems like some sort of dugout beyond there, and it hasn’t caved in.  Maybe it’s the end of the tunnel.”

“Did you say you can see somebody in there?” asked Blake.

“Yes; figures moving about.”

“Call to them.”

“Maybe they’re Germans!” exclaimed Charlie.

“They probably are,” Blake answered.  “But we’ve got to be rescued from here and take our chance with them.  It’s better than being buried alive.  Hello, there!” he shouted.  “Help us get out!” and he began tearing at the stones with his hands.

Seeing his object, his chums helped him.  And then some one on the other side of the rocky barrier also began pulling down the stones, so that in a little while, the light becoming momentarily greater, the boys saw a way of escape open to them.