When Frank reached shore after being taken from the German cruiser, he was received courteously by the officer in command of Fort Kaiserin—one of the German fortifications along the Kiel canal. The latter questioned him at length regarding the D-16, and the lad gave what information he believed could be of no value to the enemy.

At first it was announced that the lad would be taken to Berlin that day, but later as the reader has already learned this was deferred till the next.

“If you will give me your parole,” said the German commander, “I shall be glad to allow you the freedom of the fort.”

“I appreciate your kindness,” replied Frank, “and I am sorry that I do not feel myself at liberty to accept.”

The officer shrugged his shoulders.

“There is little danger of your getting away,” he said. “However, I find it my duty, in view of your refusal, to order you confined.”

Frank bowed but said nothing.

Half an hour later he was conducted to a cell at the end of the fort nearest the outer wall. Here he sat all day, being well treated and well fed, but allowed no liberty.

“By George!” said Frank to himself right after noon, “I have a notion to try to get out of here. I don’t know whether I can get away or not, but I believe I shall take a chance at it. I don’t want to be cooped up in Berlin for the next few years if I can help it.”

Accordingly he mapped out a plan, which he decided to put into execution when the jailer brought his evening meal.

The afternoon passed slowly, but at length the time to act came.

A key grated in the cell door and the jailer entered, carrying a tray of food.

“How is the weather outside?” asked Frank.

The jailer was a jovial sort.

“Fine,” he replied. “Too bad you cannot be out to enjoy it.”

“It is too bad,” Frank agreed. “Well, what do I get for supper?” and he bent over as though to examine the tray.

“Soup——” began the jailer, but he said no more.

Straightening up suddenly, Frank caught the man by the throat with a vise-like grip, while he clapped his other hand over his mouth, stifling an outcry. Then, suddenly, he drew back his right fist, and before the German could free himself, struck him full on the point of the jaw.

The German toppled over like a log.

Frank picked him up gently and laid him on the bed, where he gagged him with his handkerchief.

“Now to get out,” he said.

He approached the door and peered about. There was no one in sight. He picked up the jailer’s keys and, stepping into the corridor, closed the door behind him and locked it.

“Now if I can just avoid detection till I get out of here,” he told himself.

Quietly he walked along the corridor, to where he knew the door to be. In a room just beyond he heard voices. He approached carefully and peered in.

In a far corner, half a dozen German soldiers were busily engaged with a pack of cards. They were so engrossed in their game that they paid no attention to Frank as he stepped quietly into the room, walked boldly across it and disappeared through the door on the opposite side.

Outside Frank drew a long breath.

“So far so good,” he muttered.

Getting into the open was now a simple matter. Frank knew full well that a careful watch was not being kept, so now he walked boldly on.

Turning eastward and feeling that he was free at last, he broke into a quick trot.

This almost proved his undoing, for suddenly a voice out of the darkness challenged him.

“Who goes there?”

“Friend,” replied Frank.

The challenger approached. One glance at his British naval uniform was enough. The man attempted to bring his gun to bear, but Frank was too quick for him. Jumping suddenly forward, he knocked up the weapon, and then, with two terrific punches, laid the man low.

But the sound of this scuffle had attracted half a dozen other figures and now Frank found himself surrounded.

“They will have to fight to take me back there,” he said through clenched teeth, and not waiting for his foes to come to the attack, he plunged into the midst of them.

When Jack and Lord Hastings advanced toward the struggling knot of men they had no idea what was going on; but Frank, over the shoulders of his foes, saw them.

“Jack! Lord Hastings!” he cried.

His two friends were taken aback, but Jack was the first to recover himself.

“It’s Frank!” he cried, and dashed forward.

Lord Hastings was not a moment behind him, and these reinforcements, seeming to be two German officers, disconcerted Frank’s adversaries, who drew off.

But the sound of Jack’s voice speaking in English convinced them that something was wrong, and they sprang forward again.

“Crack!”

With a single movement Jack had drawn his revolver and fired.

One man fell.

“Crack! Crack! Crack! Crack!”

The firing became general, but the Germans were taken at a disadvantage as their opponents had been the first to draw.

Three Germans only now remained on their feet, and as Lord Hastings, Jack and Frank advanced upon them they turned and fled.

“Quick!” cried Lord Hastings. “Follow me! We’ll have the whole garrison upon us in a moment!”

He turned and dashed back along the dark road, Frank and Jack following.

From behind came the sounds of a terrible commotion. The garrison was aroused, and the fugitives realized that speed was the only thing that would save their lives.

Without a word they sped along as fast as their legs would carry them. In the darkness Lord Hastings would have passed the spot where they had hidden the launch had not Jack’s keen eyes recognized it as he flashed by.

“Wait!” he called, stopping so suddenly that Frank, who was directly behind him, bumped him and almost knocked him off his feet.

Lord Hastings also stopped.

“What’s the matter?” he demanded.

“You have gone too far,” cried Jack. “Here!”

He stepped in under the trees and laid a hand upon the launch. Frank and Lord Hastings lent a helping hand, and soon the little boat was floating upon the water.

“Quick! In with you!” cried Jack, as he fairly pushed his two companions into the boat.

Then he gave it a hard shove and scrambled in himself.

At that moment, from behind, came the sound of running footsteps and a hoarse voice of command:

“Fire!”

There was a deafening crash and a hail of bullets sped over the little boat, for at the command fire Jack had cried out:

“Down!”

All three lay flat in the bottom of the boat, Jack, with one hand behind him, doing the steering from that position.

A second and a third hail of bullets from behind passed without harming them, and then no more came.

The three sat up in the boat.

“Pretty close, if you ask me,” said Jack.

“I should say so,” replied Frank. “We---- Hello!”

“Now what’s the matter?” demanded Lord Hastings.

“Listen!” whispered Frank.

All three listened intently.

From astern came a choking “Chug chug.”

“We are followed!” exclaimed Frank. “We shall have to hurry. Is this as fast as this thing can move?”

Jack was tinkering with the motor.

“I guess it is,” he said at last. “However, we have quite a start, and with luck should be able to reach our vessel before they can overtake us.”

As swiftly as she could go the launch made for the spot where the submarine, still submerged, awaited them.

Brennan, whom Lord Hastings had left in command, was fully alive to his responsibility. Steadfastly he remained at his post, peering intently through the periscope. For hours he had been there, and now his patience was rewarded.

In the distance he could make out a small boat dashing madly toward him. Quickly he gave the signal to rise, and when the submarine again floated upon the surface of the water, he ascended to the bridge.

As the boat drew nearer he recognized its occupants; and then, for the first time, he realized that they were followed. Prompt action would be required when they were on board and he knew it.

With a hoarse bellow he called the crew to their places, and advanced to the side of the vessel to lend a hand to the officers when they should arrive.

At last they reached the side, under a volley from the pursuing German launch. Lord Hastings clambered aboard and Frank and Jack followed in rapid succession. As they set foot on deck the latter shouted:

“Below! Quick!”

All made a mad dash and in a moment the entrance through the conning tower was hermetically sealed behind them.

“Submerge!” cried Lord Hastings; and as the D-16 once more sank from view, her commander wiped the beads of perspiration from his forehead with his sleeve.

“Whew!” he exclaimed. “Pretty close! Pretty close! But we are all safe, and that’s enough!”

“Right, sir,” said Jack. “And enough’s a plenty!”