"The reason," replied Frank, "is perfectly simple. It's because the main British fleet is out there waiting for you fellows. After we chased your fleet back----"

"But you didn't chase us back. We retired when the battle was won."

"Oh, you retired when the battle was won, eh?"

"Yes; that's what the official report says."

"But it doesn't say who won the battle, does it?" asked Frank, with a grin, in which his friends were forced to join.

The young officer gazed from one to another, and Frank continued:

"Now, I'll tell you something you don't seem to know. We were pursuing the German fleet when two of our vessels crashed in the fog. That's how we happen to be here now."

"But I tell you that is not possible," protested the German.

"It may not have been considered possible," returned Frank, "but it's a fact, all the same."

"You mean, then, that the official report is not true."

"Well, that's my personal opinion of it," Frank admitted.

"Sir!" exclaimed the young German, drawing himself up suddenly. "You have insulted the German navy--and me with it. Were it not that you are our guests aboard this warship, I would demand satisfaction."

"Look here," exclaimed Frank. "I didn't mean to hurt your feelings. I was just telling you the facts in the case. I----"

The young German faced him angrily.

"Your half apology only adds to the insult," he said. "I shall leave you now."

With this he drew himself up stiffly, turned on his heel and stalked away. Frank gazed after him amusedly.

"Now what do you think of that?" he exclaimed.

"You should have known you couldn't convince him," said Jack.

The three friends walked along the deck gazing out over the water. Half an hour later, as they were about to go below, Frank caught sight of a figure in the uniform of a German lieutenant, who was eyeing them closely.

There was something familiar about that figure and unconsciously the lad gave a start. He called Jack's attention to the man, and the latter, seeing that he was the subject of discussion, quickly withdrew.

"I've seen him some place," said Frank.

"And so have I," Jack declared. "There is some thing strangely familiar about him. Say! It's unpleasant when you know a man and can't place him."

"Let's hope he is not some old enemy come back to life," said Frank, quietly, as they returned to their cabin.

CHAPTER XXIII

AN UNKNOWN FRIEND

Bremen. The greatest of all German shipping centers, and, before the outbreak of the European war, one of the greatest seaports in the whole world.

Even on the third day of June, 1916, when the German warship on which Jack, Frank and Harris were prisoners steamed into Bremen the port was alive with activity. Great German merchant ships, useless since the war began, appeared deserted, but other and smaller craft dashed hurriedly hither and yon.

"Why all the excitement?" was Frank's comment, as the three stood well forward while the warship steamed through the harbor.

"Several reasons, I guess," said Jack. "One is that half of these small vessels ply between Bremen and Scandinavian ports in spite of the British blockade; and the other reason probably is the fact that the city is celebrating the great naval victory."

"Naval victory?"

"Sure; the battle of Jutland. The German people have been told that the German fleet won; and now the people are celebrating. See all those flags? Why else would they be displayed so profusely?"

"Because Germany is at war," said Frank.

"Oh, no they wouldn't. You remember we were in Hanover once while the war was in progress. You didn't see all those flags about like that."

"I guess you're right."

At that moment a German officer approached the three friends.

"I've something of interest to show you," he said; "something that will be of interest to all the world presently."

"We shall be glad to see it, whatever it may be," replied Jack, courteously.

"Look over the side there," said the German, pointing. "Do you see that long, low shape in the water?"

"Why, yes," said Frank. "Looks like a submarine."

"That's what it is. Can you make out the name?"

The three friends peered at the object closely.

"D-e-u-t-s-c-h-l-a-n-d," Frank spelled it out.

"Yes, the _Deutschland_" replied the German officer; "and, within a month, the whole world will be talking about her."

"What's she going to do?" asked Frank. "Sink the whole British fleet?"

The German officer smiled.

"No," he replied quietly. "The _Deutschland_ will be the first of a fleet of merchant submarines to ply between Bremen and the United States."

"What?" exclaimed Jack, in the utmost surprise. "You mean that submarine will try and run the English channel and make for the United States?"

"Exactly."

"But it's impossible," said Frank.