ne of them,
sullenly.

"Then who was crying for help?" persisted the young captain.

"See here, cap'n, you are on the wrong trail," came from the older of
the regulars. "Me and Bill's jest been having a little rumpus between
ourselves. We meant no harm by it."

"I don't believe you," came from Major Morris, promptly. "There is
some mystery here, and as sure as you're born I'm going to find out
what it is!" he went on.

The major had scarcely finished when Ben's eyes fell to the floor, and
he saw the outline of a trap-door under one of the regular's feet. One
edge of the door was raised about half an inch above the floor proper,
as if the door had been opened and not put back evenly into place.

"Major, look at that trap-door!" he cried. "I'll wager they used it
while we were coming up the outside stairs."

"You must be right, captain. If you'll--"

"We didn't use no trap-door," shouted the younger of the regulars, but
he appeared much disconcerted over the discovery Ben had made.

"Captain, I have them covered," came from Major Morris, as he brought
out the two pistols with which he had wisely provided himself.
"Perhaps you had better investigate."

"I will," returned the young captain, and backed out of the room. The
regulars wanted to stop him, but aiming his weapons at them the major
told them to hold their peace.

"If everything is all right, you won't be harmed," he said. "But it
doesn't look right to me. You have no business here, for one thing."

"And what business have you here?" demanded the older regular. And
then he changed his manner. "We were captured in the fight of last
week, and were just trying to get back to our lines again."

"We'll talk about that when my friend the captain gets back, my man.
If we are treating you unjustly, I'll apologize and do the handsome
thing by you," he added.

In the meantime Ben was making his way down to the bank of the stream,
under the mill, with all possible speed. It was extremely dark, and he
had to pick his way with caution for fear of tumbling into some ugly
hollow. Below the mill was a fall of water, and here the stream ran
between a series of sharp rocks.

Ben had just gained the bank of the stream when a low moan reached
his ears. At first he could not locate the sound, but presently
discovered that it came from the vicinity of the rocks. Feeling his
way along he managed, but not without great difficulty, to gain the
top of the rocks. Here he saw