little party began groping its way along. Ned reached out a hand on
either side as he went forward. His hands came in contact with walls
that appeared to be made of stone. The dampness had gathered in great
drops on the surface. A slime had been deposited that made Ned shudder
as he felt it. He knew, however, that this was no time to permit an
interruption through squeamishness.

There was now no guiding light in advance, and the boys cautiously
picked their way along the stones, with Ned feeling every inch of the
way before he set his foot down. Directly the lad heard another
warning hiss. This time the sound was closer than formerly.

"Put your hand on my shoulder," came the whispered command.

Ned followed this instruction immediately. He judged by the height to
which he raised his hand to rest it upon the other's shoulder that the
stranger was a person of about his own build. His sense of touch also
told him that the other's clothing was of a material similar to the
khaki uniform he himself was wearing. A faint odor of gasoline and
grease assailed his nostrils, particularly distinguishable because of
the damp air in which the party was traveling.

Suddenly the boys were startled by the sound of an explosion that came
faintly to their ears. The earth in their vicinity trembled.

"What's that?" asked Ned in a whisper. "What's going on?"

"Hush!" replied the guide. "The Germans are making some improvements
in the town. They are blowing down some dangerous walls. Now keep as
quiet as you can and follow me. We'll have to hurry!"

Ned made no further attempt at conversation, but obediently gave his
entire attention to following the strange person in advance.

Before the little party had traversed the passage to any considerable
distance they heard several other explosions similar to the first. One
particularly louder than the others was followed by the sound of small
pieces of rock tumbling from the roof and walls of the passage. Ned
pressed still closer to his guide, while Jack and Harry needed no
urging to make them crowd up to Ned in their impatience.

Not far from the point where the boys had noticed the pieces of rock
falling the guide turned a corner abruptly. Ned wondered how he was
able in the intense blackness to distinguish so accurately the spot for
making the turn, but refrained from making any comment.

As he followed the guide around the corner the lad's foot struck
against an o