alley and drop down here, there
may, for all we know, be others in hiding further down."

"That's a fact," Chester admitted.

"I wish we knew who the people are who are entering the tunnel," Will
said. "It may be the robbers, or the detectives, or the sheriffs. It may
even be your father, for all we know."

"Well, shall we move on down to see if we can find an outlet?" asked
Chester. "That seems to me to be the best thing to do."

"It strikes me that that is the only thing we can do."

The boys were moving on down the almost level floor of the chamber in
absolute darkness, for they did not consider it safe to show their
electrics when they heard a chuckle in the darkness.

They drew up instantly and listened.

"That's Tommy!" declared Will.

"It can't be," replied Chester.

"Don't you suppose I know that chuckle?"

"Well, the boys weren't with the men I saw near the mouth of the
cavern," declared Chester.

The boys listened again for some moments, and then caught sight of a
finger of light far up the slope of the tunnel.

"That's a searchlight!" declared Chester.

"It surely is," agreed Will.

While the boys stood in the darkness, waiting and listening, they heard
a voice which they had no difficulty in recognizing as that of Tommy.

"This is some basement stairway," the boy said.

The next moment George's voice was heard.

"We must be about nine stories under ground by this time," he said.

There was silence for a moment and then Tommy was heard to ask:

"What's become of our chaperons?"

"There's something doing out in the lobby," the boys heard George say,
"and I guess they went back to defend their home and fireside."

"I hope they'll get a couple of bullets in their domes!" declared
Chester. "They've helped us out several times, but they've never done it
because they wanted to do us a favor!"

"Keep still a minute," Will suggested. "Let's hear what those boys are
saying. I'd like to know who they're talking about."

"I haven't got much use for the detectives," they heard George saying,
"but I hope they'll get these train robbers and get them good and
plenty!"

"So it's the train robbers!" exclaimed Will.

"I don't believe the detectives will ever get within a mile of the
robbers," the boys heard Tommy say. "If anybody catches the outlaws,
it'll be the sheriff of Fremont county."

"The man at the head of the cowboys?" they heard George ask.

"That's the fellow!" Tommy replied.

"H