When Herman Blatz, alias Lieut. Serge Larko of the Rubanian secret police, was alone in his room late that afternoon preparing for supper, he was torn between conflicting emotions. He had reached Bellevue safely. He was even inside the plant of the National Airways, accepted as a German civilian observer. The opportunity for him to wreck the Goliath might present itself at any moment but two mighty emotional forces were at work. One was his inherent love for anything man-made that could conquer the elements. Only that afternoon he had viewed the greatest of all airships and he quailed inwardly at the thought that his task was to destroy the mighty craft.

He heard the call for supper and descended to the dining room where he was seated at the head table with Andy, Bert, Harry, Andy’s father and Captain Harkins. There was a vacant chair at his left and he wondered who the late-comer would be.

Conversation at the table was devoted almost solely to topics centering around the Goliath and the young Rubanian airman reveled in the sheer joy it brought him. For the time he forgot his ominous mission and was light-hearted and gay.

Supper was half over when a quiet man slipped into the chair beside him. Andy turned and introduced the late arrival.

“Mr. Blatz,” he said, “I want you to know Merritt Timms, chief of the secret service agents here.”

Blatz acknowledged the introduction mechanically and Andy, watching his every move and facial expression, failed to see any note of alarm. It was well for Blatz that Andy’s eyes could not penetrate beneath the surface for Blatz’s mind was working rapidly.

The chief of the secret service agents at Bellevue seated beside him! Had he aroused suspicion already? Had there been a slip somewhere along the line; could these alert Americans know his identity and be playing with him, waiting for him to make a slip so they could send him to some military prison?

He knew the careful workings of the Gerka and he doubted that a slip had been made. That thought gave him some reassurance and his gay attitude returned.

They finished the meal and chairs were pushed back.

“I’m going over to the hospital,” said Timms to Andy. “Want to go along and hear what Dubra has to say?”

Andy darted a glance at Blatz. He saw the civilian observer start ever so slightly. It was hardly more than a tremor but it helped to verify Andy’s suspicions.

“I’ll go,” he replied. “Perhaps Blatz here would like to come with us?”

“Yes, of course,” replied the other. “Some mechanic hurt?”

“A little,” replied Timms. “A couple of bullets hurt him. He was an agent of the Gerka, Rubanian secret police organization, planted here to damage the hangar. He failed and the guards didn’t miss when he tried to escape.”

“I’m surprised to hear that,” said Blatz. “I didn’t suppose anyone would direct any destructive efforts toward the Goliath.”

“We’ll be surprised if anyone else does,” said Timms, “for we know that Alex Reikoff, dictator of Rubania, would like nothing better than to hear about the destruction of the Goliath. As a result, we’ve taken every precaution that is humanly possible.”

“That is wise,” said Blatz, “for in Europe we have come to fear Reikoff as a menace to the peace of the world.”

They were in the doorway of the hospital now and Blatz saw Andy’s keen blue eyes boring into him, probing as though questioning the truth of his words. He felt that his answers, especially the reference to Reikoff as a menace, had been well put.

A slight infection had set in on Dubra’s right leg and the Rubanian was restless with pain.

“Hello, Dubra,” said the secret service chief. “Just dropped in to see how you are getting along.”

“They’re killing me,” cried the man on the bed. “My leg hurts so.”

“They’re doing no such thing,” replied Timms. “The doctor here is making every effort to save your worthless life. Have you got anything else to add to what you said the other night?”

Dubra’s eyes were bright with fever but his mind was clear and he shook his head.

Blatz kept well in the background. He had lost the ally Reikoff had told him he would have. Dubra, over-anxious to cause harm, had been caught and wounded. His usefulness as an agent of destruction was at an end and Blatz would have to go on alone. Perhaps it would be easier that way.

There was no more information to be had from the wounded Rubanian and they left the hospital. When they returned to the hotel, Blatz excused himself and went to his room. Timms signified his intention to do likewise but changed his mind when Andy insisted that they take a walk together.

“What’s the idea?” the secret service chief asked when they were well away from the hotel and walking in the open.

“It’s Blatz,” said Andy. “There’s something about him that doesn’t ring true.”

The assistant pilot of the Goliath related the incident of the afternoon with the fake story of the adventure at Friedrichshafen.

“That sounds a little fishy,” admitted Timms, “but that’s not enough to accuse a man of being a spy.”

“I realize that,” admitted Andy, “but you should have seen him tonight when you asked me if I wanted to go to the hospital and see Dubra. Blatz’s face paled and he trembled ever so slightly. No one else noticed it but I had been watching him closely.”

“Still there is nothing definite,” insisted Timms.

“There’s enough so that I’m not going to let him get very far away from me,” replied Andy. “Can’t you start a quiet tracer through the secret service; find out where and when he landed; how he came to receive the permission from the war department and anything else your people in Europe can dig up?”

“It might be rather serious if your suspicions proved unfounded,” said Timms.

“I’m willing to take the risk,” replied Andy.

“Then I’ll see what can be done,” promised the secret service chief.

Events during the next month at Bellevue were quiet enough. Andy kept a close watch of Blatz, but the German observer’s conduct was model. He confined his activities solely to observance and taking notes on the parts of the Goliath to which he was allowed access and he made no move to delve into the military secrets which were a part of the giant craft.

Bert and Harry had been busy with the installation of the intricate radio equipment which was a part of the Goliath. Late in April they completed their joint task and Bert announced that the communications apparatus was ready.

Assembly of the gondola had been completed, motor crews were busy tuning up the 12 giant engines which were to provide the power and fitters worked overtime on the installation of the luxurious furnishings of the lounge and sleeping quarters in the passenger cabins.

The gondola of the Goliath was a two-deck affair. In the fore part of the lower deck was the control and operations room with the communications room just behind. The main lounge was located on this deck with the dining room and the chef’s quarters at the rear of the gondola. An enclosed promenade deck, encircled the lounge and dining room. The upper deck was devoted solely to passenger cabins, which were fitted like the staterooms of a Pullman. Every modern convenience for the comfort of travelers had been built into the gondola and the Goliath was truly a revelation in luxury.

Blatz was enthusiastic in his praise of the great machine and Andy was forced to admit to himself that his earlier suspicions appeared unfounded. He relaxed his vigilance somewhat and the secret agent of the Gerka sensed this change in the assistant pilot’s attitude. Between them a real friendship started to develop and it was only natural that Bert and Harry were included in this feeling of comradeship.

On more than one occasion Blatz proved his sound technical knowledge, which could have been gained only at Friedrichshafen, a fact which influenced Andy in quieting his suspicions. In addition, there had been no report from the Washington headquarters of the secret service and it appeared that Blatz’s record was all right.

Shipments of helium, the life-blood of the Goliath, were arriving daily from the Texas gas fields. The long, narrow cylinders were stacked in rows outside the hangar. When needed they would be trucked inside, the valves opened, and their contents would flow into the gas cells inside the duralumin hull. In this respect the United States led all the other nations in its precious supply of helium, a non-inflammable gas. Some of the Europeans were forced to use hydrogen, a highly inflammable gas, the use of which had resulted in some of the major dirigible catastrophes.

Work on the Goliath was well ahead of schedule and when Bert and Harry finished their work on the radio equipment, Harry announced that it would be necessary for him to return to Brooklyn at once for a final test of the equipment of the Neptune.

The submarine was to leave soon and Andy and Bert obtained leave to accompany Harry on his return east. When Blatz heard of the plans, he asked permission to accompany them. It would give him an opportunity to visit the American headquarters of the Gerka in New York.

“You might just as well make it a real holiday,” Andy’s father said when apprised of their plans. “One of our cabin monoplanes will be in tomorrow and I’ll see that you are given the use of it for a week. Then you can fly east together.”

The suggestion appealed to them and they accepted with enthusiasm. Two days later they were ready to depart. After stowing their luggage into the baggage compartment of the trim, fast National Airways monoplane, they each took farewell looks at the Goliath and then climbed into their places.

Andy was at the controls with Blatz in the seat beside him. Bert and Harry were sprawled in comfortable wicker chairs to the rear. The plane skimmed across the field and took off in a steep climb, circled the field once, and then headed northeast in a bee-line for New York.

The mountains, their crests covered with the fresh green of early spring foliage, reared their misty heads to the east. They would cut diagonally across them and Andy held the stick back and watched the altimeter climb. At five thousand he leveled off and settled down to the trip. They had plenty of gas to make it on one long hop.

Blatz was enjoying the trip, the rolling country beneath, the mountains which they were approaching and even the thrill of being in the air, which never grew old to him. His eyes sparkled and there was a bright glow to his cheeks. He’d like to get his hands on the controls and see how this American commercial job handled.

An hour later Andy turned to Blatz.

“Ever handled a ship like this?” he asked.

“I’ve done a little flying,” admitted the European.

“Think you could handle it?”

Blatz nodded eagerly and Andy slipped out from behind the controls which the other took over.

Andy watched him keenly and noticed that Blatz settled into his chair like a veteran. His touch on the controls was firm but light and, unlike the beginner, he did not over-control.

The air over the mountains was rougher and Andy wondered how Blatz would come through. His question was soon answered. A down draft swirled them downward three hundred feet in the twinkling of an eye. A novice would have been panic-stricken, but Blatz gave her the gun and flipped out of it nicely.

“Good work,” said Andy.

“More luck than anything else,” was the reply, but Andy was very much inclined to disagree. There was no question in his mind now. Blatz was not only a good dirigible man but he was an expert flyer as well. The long-allayed suspicions Andy had harbored in the first weeks the civilian observer had been at Bellevue were re-awakened. He would communicate his distrust to Bert and Harry when they had a chance to talk alone. Until now he had kept his misgivings to himself but he felt that it was time the others knew how he felt.

They lunched over eastern Pennsylvania with the plane clipping the miles off at 110 an hour. Sandwiches had been brought in a liberal supply but the cool air had whetted their appetites and the basket of lunch soon disappeared.

“Oh, boy,” said Bert. “Wait until I get to New York and sink my teeth in a big, juicy steak. Honestly, I’m almost starved. Those sandwiches were just teasers.”

“How long before we’ll be in?” asked Harry, who likewise confessed that the lunch had not satisfied his hunger.

“Another hour,” replied Andy, who was back at the controls. “Next time we’ll bring a restaurant along. From the way you fellows complain someone might get the idea you’d been working this morning.”

Fifty-five minutes later they dipped over the National Airways field on the Jersey side and Andy nosed down to land. Blatz touched his arm.

“If Bert and Harry won’t starve for five more minutes,” he said, “I’d like to see New York from the air.”

“We’ll manage to hold out another few minutes,” conceded the hungry pair, and Andy headed the monoplane east across the Jersey flats.

They dipped a wing in salute as the Statue of Liberty was passed and climbed steeply as they approached the Battery. On up town they sped over the canyons between the skyscrapers where hurrying crowds of shoppers were thronging the streets. The Empire State’s gleaming tower was ahead, then beside, and then behind them. The Chrysler spire glittered in the sun and they looked down on the crowds in Times Square. Central Park was a fleeting panorama. Then they were over the Hudson, back to Jersey and sliding down out of the skyway with motor idling. They touched gently and rolled to a landing in front of the main control station where the number of their plane was taken and they were assigned to a hangar. Andy taxied the monoplane down the line to the No. 5 hangar where mechanics were ready to take it in charge.

“How did you like your aerial view of New York?” Andy asked Blatz.

“It was marvelous, breath-taking,” laughed the other. “In Europe we have no city to compare with it. Your buildings; they go into the clouds.”

“I’ll say,” replied Harry. “I’ve been on the Empire State tower when the clouds were so thick you couldn’t see the street.”

They entered the main administration building at the airport, cleaned up, and then took a taxi for New York. Through Jersey City and under the Hudson they went in the Holland Tubes and then through the maze of mid-afternoon traffic to their hotel just off Times Square.

While Andy was registering for the party, Bert saw the sign above the door of the grillroom, and, with a “See you later,” departed to order the steak he had promised himself.

Andy, Blatz and Harry went up to their rooms, assured themselves that the double quarters were satisfactory, and then went down to join Bert in the grill.

“I ordered steaks for everyone,” said the radio operator of the Goliath. “Anyone have any objections?”

There was no vocal protest and the steaks were placed before them a minute later.

“I’ve got to go over to the shipyard and report that I’m in town,” said Harry. “Anyone like to run over to Brooklyn now and see what the Neptune looks like?”

“Count me in,” replied Bert. “I want to see what kind of a tin can you’re going to use in your attempt to reach the North Pole.”

“How about you two?” asked Harry, turning to Andy and Blatz.

“I’ll be glad to go in the morning,” said Blatz, “but just now I’m a little tired. I’ll stay here at the hotel, rest a while, and then perhaps stroll out and look around the city a bit.”

“You’ll have to count me out, too,” said Andy. “I’ve a few errands that must be attended to and the sooner they are out of the way the more time I’ll have to spend over at the shipyard.”

Harry and Bert departed, after promising that they would return early in the evening so they could enjoy a show together. Blatz went up to their double room and Andy sat down at a writing desk to pen several important notes. He had been writing not more than five minutes when he looked up and saw a familiar figure going through the main doorway. He recognized the German civilian observer. But Blatz had just said that he was tired and was going to his room to rest?

Without waiting to ponder the question, Andy picked up the note he had been writing, stuffed it in his pocket, and hurried toward the entrance.

It was late afternoon and dusk had settled but he reached the street just in time to see Blatz step into a cab. There was something furtive, mysterious in the other’s manner and Andy decided to follow. He motioned for a cab cruising by to stop. The driver was an alert, keen looking fellow and he responded instantly when Andy spoke to him.

“Keep that cab ahead in sight,” said Andy, “and there’s an extra five for you.”

Gears meshed harshly as the cab lurched ahead and Andy started on one of the strangest adventures of his life.