of
wagon wheels.

"Somebody has been in the habit of driving right in here!" exclaimed
Tom. "We are sure to get out!" and his face showed his relief.

"Hark! what's that?" cried Sam, and shrank back as a strange rumbling
was heard. "Is it an earthquake, or a landslide?"

"It's thunder, that's all," said Dick, a minute later, as they listened.

"To be sure--the storm was on us when we fell into the first hole,"
answered the youngest Rover.

"Perhaps we can be glad we are under shelter--if the storm is going to
be a bad one," came from Tom. "But, come on, I want to see daylight
again."

He moved on and then gave a cry of astonishment.

"Look!"

His brothers did so. On one side of the cave were piled thirty or forty
packing cases. The majority of them were empty, but three, directed to
one Jackson Dwight, Carwell, were full and nailed up.

"Well, I never!" murmured Sam. "Dick----"

"The freight thieves!" ejaculated the eldest Rover. "Don't you remember
what was in the paper before we went south, and what was in again only
yesterday? They have been missing freight from Carwell and Boxton and
half a dozen other stations for over a year. The thieves must have
brought their stuff here and then taken some of it from the packing
cases and carted it away again."

"It certainly looks like it," answered Tom. "Only three full cases left.
I wonder when these were taken?"

"Most likely only a short time ago," said Dick. "The cases look new."

"Do you suppose any of the freight thieves are around? If they are we
want to keep out of their way--if they are desperate characters."

They moved on, and then Dick called a sudden halt.

"I can see daylight ahead," he said. "And somebody is moving around. Let
us put out the torches."

His suggestion was speedily followed, and the three Rover boys advanced
with caution. At its outer end the cave became broader while the roof
was only about ten feet high.

"Hullo, here's another surprise," whispered Dick, as they came closer to
the opening. "Look at that!"

He pointed to one side of the cave and there the others saw an
automobile runabout standing and on the seat two men dressed for a tour.
They were talking to a third man, who was lounging against a front
wheel, smoking a brier-root pipe.

"Maybe they are the freight thieves," whispered Tom. "Let us get out of
sight and listen to what they have to say."

It was an easy matter to keep out of sight, for the walls of the