If Jimmie should be killed in there,
the bomb should avenge his death. The ruins of the temple and the
work-shop of the plotters should all ascend heavenward in one grand
explosion. After a time, however, his fears were set at rest by the
appearance of the boy, who came up to the doorway with a grin on his
face.

"Nothin' stirrin' in there now," he said. "Come on."

It seemed plain now that those interested in the work which was going on
underground were depending on outside watchers to protect them. The fire
in a rude forge which stood at the distant end of the chamber was dying
out when the boys reached it, and the place was only dimly lighted.

On one side of the room was a pile of gas-pipe, cut in six-inch lengths.
In a corner, far away from the fire, and half buried in the earth--a great
paving stone having been removed to make way for the excavation--were tin
vessels tightly covered. After his experiences of the night, Ned did not
have to inspect the contents of these tins. He knew very well that they
contained high explosives.

"There's stuff enough here to blow up the continent of South America,"
Jimmie said, pointing at the gas-pipe lengths and the tin vessels.

"And they are getting the material in shape to do the work," Ned added.

"Yep," Jimmie answered. "We've caught 'em with their workin' clothes on.
We've got to the bottom of the plot."

"You go too fast, son," Ned replied. "We haven't got a single clue to the
men higher up. It is probable that we have discovered the plant of the men
who are planning to destroy Uncle Sam's big job, but the work we have
undertaken has only begun."

"Why, catch these men," said Jimmie, "an' you've got 'em."

"Got these men, yes, but the chances are that even they do not know the
men who are at the head of the conspiracy."

"Some one is puttin' money into it, anyway," the boy suggested.

"Yes, and we don't even know the interests which are doing it," said Ned.

Ned now busied himself about the chamber, having closed the door so that
the light of his matches would not show. There was, of course, danger that
the watcher might descend the stairs and discover the closed door, but
there was also the chance that he might attribute the changed situation to
accident.

Presently Ned came upon a battered old writing desk standing on the head
of a large barrel. The slanting top was locked down, but the boy soon had
it open. Its contents consisted of two rolls of drawing