had thrown the light, while
another was fumbling at the bar. The door swung open, and the three
walked in.

"Come on," whispered Jack.

Not waiting for the others, realizing it would be only a moment or two
before their disappearance from the cell would be discovered, he
leaped from hiding, tore down the little hall like a whirlwind, dashed
against the great door and swung it into place. Bob, who was close at
his heels, dropped the iron bar into place.

They were not a moment too soon. Shouts of amazement and alarm came
from the room even as the door was swinging shut. And hardly had Bob
dropped the bar into the socket than those within threw themselves
against the door. So tremendously thick and strong was the latter,
however, that with its closing all sound from within was reduced to
the merest whisper. As for trying to move it, as well attempt to push
an elephant over by hand. This those within must have realized, for
presently they desisted.

"Got 'em in their own cage," said Jack, triumphantly. And, pulling
from his pocket Tom Barnum's little flashlight, he reassured himself
the door really was barred, then mounting the stairway thumped on the
trapdoor as a signal to Frank. The latter at once raised the door.

"Come on down, Frank," said Jack. "There were three of them, and we
penned them in the cell."

Hastily he explained what had occurred.

"Now, fellows," said he. "Let's see who else is downstairs. Let's see
if we can't get out of here, so we can radio Lieutenant Summers for
help."

"But how about leaving these chaps behind, Jack?" protested Bob. "They
can get out the same way we did, and give the alarm. What we want to
do is to bring Lieutenant Summers to the scene without letting these
rascals get an inkling of what's hanging over them. If Higginbotham
and his companions escape, he'll start a search for us, and our plans
will stand a fair chance of being spoiled."

"You're right, Bob," said Jack. "But what can we do? They can't get
out of there in a minute. It will take them some time because, for one
reason, they will be fearful of our lying in wait for them, perhaps.
Meantime, we can be moving fast. Captain Folsom," he added, deferring
to the older man, "what do you think we ought to do?"

But the latter laid his sound arm on Jack's shoulder.

"Listen," he cautioned.

Muffled, but distinct, there came an outbreak of pistol shots,
followed by shouts faintly heard.

"What I feared," said Ca