"That's a good idea, too!"

The boys came at length to a brattice, which is a screen, of either
wood or heavy cloth, set up in a passage to divert the current of air
to a bench where workmen are engaged, and dodged down behind it, after
turning off their lights, of course,

"Now, come on with your old light," whispered Tommy.

As if in answer to the boy's challenge, the light showed again,
apparently but a few yards way from their hiding place.

A moment later the call of pack sounding louder than before, rang
through the passage. The boys sprang to their feet and switched on
their lights.

"Why don't you come out and show yourselves?" shouted Tommy.

"I don't believe you're Scouts at all!" declared Sandy.

There was no answer. The boys could hear the drip of water and the
purring of the current as it crept into a lower gang-way, but that was
all.

"That settles it for tonight!" exclaimed Tommy. "I'm not going to
hang around here waiting for Boy Scouts who don't respond to signals!"

"That's me!" agreed Sandy. "We'll go to bed and think the matter
over. There may be some way of trapping those fellows."