them. Then they went on to the south
part of the grounds.

"See that, John!" said Jim in a low voice.

"A light in the tower," replied his friend; "now it's gone out again."

They stood watching with breathless interest. There are lights and
lights. Some are the mere commonplace of domestic peace set on a round
table in a cozy room with children intent on the Frontier Boys. Then
there is the weird light of a lantern moving unevenly across a field, or
revolving along a hidden lane, and there is something of the dramatic in
its yellow flame. Finally there is the light that shines under strange
circumstances or peculiar surroundings that has a mystery of its own, a
beacon of danger, or of sudden death.

"It is again on this side, only higher up," announced Jim; "somebody
going up those stairs, that's what it is."

In a few moments the powerful lamp illuminated an upper room and they
saw the interior distinctly. But what fastened their attention was the
sight of a head that showed just above the sill of the windows. It must
be the head of a child to reach no higher. But what would a child be
doing up in that lonely tower. Jim gripped his companion's arm.

"It's that infernal Mexican, Berwick!" he whispered.

"No other!" said his friend. "And that light is a signal."

"Can't be seen far even if the fog is thinner," objected Jim.

"Broome is close in," said the engineer decisively.

"It may be to serve as a guide for some party coming over the lonely
moor," said Jim with much shrewdness.

"Go to the head of the class, James," remarked Berwick; "that's a sound
guess for a fact."

"Guess nothing," retorted Jim; "that's a deduction as they say in the
school books. What in the deuce is that up there now!"

A canine head was outlined in an open window and then the big hound gave
tongue that went far into the night. His senses told him that an enemy
was lurking near.

"My! what a mark for a shot!" whispered Jim.

Then they heard a sharp command in Spanish and both the dog and the
Mexican disappeared from view.

"We had better move along, Jim," said the engineer, "or we will be on
the hot end of a chase ourselves." Without a word Jim started, but he
would not run far.

CHAPTER XIII

THE MAN IN THE GULLY

The two friends disappeared in the fog, in a southerly direction from
the house and after going for about a quarter of a mile, Jim called a
sudden halt.

"Hold on, John," he said, "there is somethin