ompanied by Slim, to make a survey there.

In ten minutes he returned, his face pale, his jaws clenched.

"There must not be a word of this to anyone," he warned them. "I am
going to report to the captain at once. Someone has been tampering with
the batteries, and he had with him a portable wireless which he
evidently intended to attach."

"You're the original little discoverer, all right," said Slim in open
admiration, addressing Joe as the lieutenant hurried from the room. "And
you certainly were game, to take the beating you did."

"Yes, he punished me some," Joe admitted. "But I got in a little work on
him, too. The only trouble is that I'm afraid I didn't blacken an eye,
or break a jaw, or otherwise do any damage that might be apparent and so
lead to the fellow's discovery."

"The nerve of it, though!" broke in Jerry.

"A German spy, doubtless masquerading as an American soldier, and right
here on a United States transport loaded with fifteen hundred soldiers
and tons of guns and ammunition."

"Yes," said Joe contemplatively, "that's the very serious part of it
all--the fifteen hundred soldiers and tons of guns and ammunition."

"Sh-h-h-h!"

Slim, who was standing nearest the door, had heard footsteps. A moment
later the lieutenant reappeared, accompanied by the captain of the
_Everett_.

When the boys had been presented, the captain abruptly requested Joe to
repeat every detail he had told Lieutenant Mackinson. As he did so the
captain gazed compassionately upon his injuries.

"And where is the instrument that you discovered?" he asked of the
lieutenant when Joe had concluded.

The young officer stepped into the battery room, returning with a small,
but evidently powerful, portable wireless transmitter and receiver.

"H'm," exclaimed the captain, examining it carefully. "Of German make."

"Exactly, sir," replied Lieutenant Mackinson, "and evidently quite
new--probably never used more than once or twice before."

"This is very serious business," said the captain impressively. And
then, addressing Joe: "Did you get a look at the other man? Would you
know him if you ever saw him again?"

"No, sir, I did not even get a glimpse of him. But I thought, sir, that
perhaps----"

"Yes," encouraged the captain in a kindly tone. "Go on with your
suggestion."

"I thought, sir," Joe continued, "that if we could find a man aboard
with his shirt torn in such a way that this piece would fit, and
especially if