ed the agitation of his chum.

"The powder has been doped!" yelled Tom. "Something has been put in it
to make it nonexplosive. It's no good. It wouldn't send that shell a
thousand yards, and it's got to go five miles to do any good. My plan
won't work."

"Doped the powder?" gasped Ned. "Who could have done it?"

"I don't know. There must have been some spy at work. Quick, run and
ask the foreman if any of his men are missing. I'll see if there's
enough of the good powder left to break down the barrier!"

Ned was away like a shot, while the others, not knowing what to make of
the strange conduct of the two lads, looked on in wonder. Tom raced
toward the cave where the powder was stored, Koku following him.

"Bless my shoe laces!" cried Mr. Damon. "Look at the dam now!"

They gazed to where he pointed. In several places the concrete spillway
had crumbled down to a ragged edge, showing that the solid wall was
giving way. The amount of water flowing over the dam was greater now.
The creek was steadily rising. Down the valley the horseman with the
red flag was but a speck in the distance.

"What can I do? What can I do?" murmured Tom. "If all the powder there
is left has been doped, I can't save the town! What can I do? What can
I do?"

Ned had reached the foreman, who, with his helpers, was standing about
the big gun.

"Have any of your men left recently?" yelled Ned.

"Any of my men left? What do you mean?

"Schlichter went yesterday," said the timekeeper. "I thought he was in
quite a hurry to get his money, too."

"Schlichter gone!" exclaimed the foreman. "He was no good anyhow. I
think he was a sort of Anarchist; always against the government, the
way he talked. So he has left; eh? But what's the matter, Ned?"

"Something wrong with the powder. Tom can't shoot the cannon and turn
aside the water to save the town. Some of his enemies have been at
work. Schlichter leaving at this time, and in such hurry, makes it look
suspicious."

"It sure does! And, now I recall it, I saw him yesterday near your
powder magazine. I called him down for it, for I knew Tom Swift had
given orders that only his own party was to go near it. So the powder
is doped; eh?"

"Yes! It's all off now."

He turned to see Tom approaching on the run.

"Any good powder left?" asked Ned.

"Not a pound. Did you hear anything?"

"Yes, one man has disappeared. Oh, Tom, we've got to fail after all! We
can't save the town!"

"Yes, we