way without hearing any sound indicating the
presence of their companions, or of any one else.

"Now that's a funny thing!" exclaimed Will. "I don't see why those boys
should go rambling about the mine at a time like this just for the fun
of the thing!"

"They never did!" replied Elmer. "You remember the shot we heard!"

"It might not have been a shot!" suggested Will.

As the boy spoke he bent over and pointed to three stones lying on the
floor of the gangway.

"There!" he said. "The boys have left a record. They not only point out
the trail, but warn, us that there is danger in following it!"

CHAPTER XVIII

TWO HOLD-UP MEN

"That's Boy Scout talk all right!" exclaimed Elmer.

"Yes, the three stones, piled one on top of the other, mean that there
is danger in following the trail. I don't understand exactly what kind
of danger can be threatening us, and so the only thing we can do is to
go on and find out," Will said with a glance backward.

The other boys now came up and a short consultation was held. It was
decided to leave Sandy and Dick at the point where the explosion had
taken place, while Will, Elmer and Jimmie followed on down the gangway.

"Now whatever you do," warned Will as the two boys were left behind,
"don't leave this gangway for a minute. If Ventner isn't out of the mine
now, we don't want him to get out. He may have the money or he may not.
That is one of the things no fellow can find out at this time, but
whether he has or not, we want him to give an account of himself before
he leaves the Labyrinth. He's got several important questions to
answer."

The boys promised to watch the passage faithfully, and the others passed
on down the gangway, flashing their lights in every direction and making
no pretense of moving quietly.

"Look here," Jimmie said after they had proceeded some distance into the
mine and discovered nothing of importance, "I have in my possession a
great idea! Want to hear about it?"

"Sure!" laughed Will.

"We're making too much noise."

"Making too much noise in order to attract the attention of a couple of
lost youngsters?" asked Elmer.

"They're not lost!" insisted Jimmie. "They've been lured away or dragged
away! We don't know how many men were in the mine with Ventner!"

"Well, produce your idea!" Elmer exclaimed.

"Well, my notion is that I ought to go on ahead of you boys, walking as
quietly as possible and without a light. If there are people w