The landing field at Bellevue was shrouded in heavy shadows of the fast-coming night when Andy dropped his Ace sportster down after the futile pursuit of the strange plane.

Merritt Timms, the secret service chief, was waiting for them when the young engineer and the radio operator climbed out of the fuselage.

“Did you get the department of commerce number on the fellow I saw you chasing?” he asked.

“I should say we didn’t,” replied Andy. “He was too fast for one thing and for another, he didn’t have any number on his wings that I could see.”

“Outlaw plane?” asked Timms.

“Yes,” replied Andy, “and a strange machine. I’ve never seen one exactly like it. I’m going over to the office and see if I can check up on its design. I’ve some guide books there that may help us.”

“How’s the Rubanian agent that was winged earlier this morning?” Bert asked the secret service man.

“He’ll come through nicely,” replied Timms, “and probably spend about the next five years in a military prison wondering what it is all about.”

“Have you had a chance to talk to him?” Andy wanted to know.

“Not yet. I’m going over after supper. Want to come along?”

“Yes,” said the young engineer. “How about you, Bert?”

“Count me in,” replied the radio operator. “It’s too bad he’s wounded. I’d like to give him a punch on the nose after all the damage he did to my radio room.”

“I don’t blame you,” chuckled Andy. “He certainly did mess things up but if he had been very intelligent he’d have recognized the installation for the Goliath and have smashed it all to pieces. I guess we’ve been lucky after all.”

When they reached the office Andy dug some reference books on airplane design out of a box and sat down to hunt for a description of the type of craft that he had encountered only a few minutes before.

“I don’t think it was an American-made machine,” he said, “so we won’t waste time hunting there. Let’s try the foreign designers first.”

British, French, Italian and German divisions failed to furnish any designs similar to the craft he had pictured in his mind’s eye.

The Russians had a low-winged monoplane but the wing mounting was too high to answer the description of the craft Andy and Bert had seen.

Andy turned on to the section devoted to the aviation activities and designs of the Rubanian air force. Here was something nearer what he sought. Pictured on one page was a low-winged machine with a streamlined fuselage that very nearly answered the description of the machine he had seen. A footnote added that planes of this type were in production at the Blenkko works near Kratz, the Rubanian capital, but that it was possible minor changes might be made in them when they were put through actual air tests.

“How does this picture strike you?” Andy asked Bert.

“Looks almost exactly like the monoplane we chased,” replied the chubby radio operator.

Merritt Timms was intensely interested in the description of the Rubanian plane.

“I’m not surprised,” he said, “and I have a hunch we’ll find that it was a Rubanian monoplane.”

“But how could it get clear over here?” asked Bert.

Timms pointed at the specifications of the monoplane which were printed under the picture.

“Cruising range 7,000 miles,” read Bert.

“That would give a good flyer an ample margin to fly from Rubania to Bellevue,” said Timms, “and such a feat isn’t at all impossible.”

“You talk as though you thought the Goliath was in great danger of damage by Rubanian agents,” said Bert.

“I don’t think now; I know,” replied Timms gravely, “for you may be sure that there is danger connected with anything in which Alex Reikoff, dictator of Rubania, is interested. Will you write a brief description of this plane?” he asked, turning to Andy.

“It won’t take five minutes,” promised Andy.

“Thanks,” said Timms. “I’ll have a complete description broadcast and we’ll be sure to pick him up somewhere. He can’t fly on forever and he’ll find that disobeying Uncle Sam’s orders and flying over a forbidden area is not to be joked with.”

Andy wrote a brief but thorough description of the mystery plane and Timms departed to get his message on its way to the broadcasting stations from which a complete description and warning to watch out for the gray monoplane would soon be sent to hundreds of thousands of listeners.

“Think Timms will be able to pick up the flyer of this Rubanian plane?” Bert asked.

“It will be something out of the ordinary if he doesn’t,” replied Andy. “Timms may be a little slow to get started but once he is on the job he is like a bull dog; he never gives up.”

Andy made sure that all of the precious specifications for the Goliath were in the big steel vault before he locked the office. They walked down to the one hotel, where they had made their home while in Bellevue, and cleaned up for supper. A regular mess hall had been built at the plant for the crews, who worked, ate and slept in the buildings erected beside the hangar, but technicians and crew foremen lived at the hotel.

The two long tables in the dining room were well filled when Andy and Bert entered and they were joined a minute or two later by Timms.

“The alarm will be all over the country in another fifteen minutes,” said the secret service man, “and we ought to have some news either tonight or the first thing in the morning.”

Structural experts, gas experts, motor specialists and expert fitters were at the table and the talk, as it always did, centered on the Goliath, how much progress had been made that day, what they would do the next and to speculation on the exact day the big ship would take the air and what would be its destination on its first official flight.

“Any news on where we’ll go on our first long trip?” one of the motor experts asked Andy.

“Sure,” replied the young engineer. “We’re going to the North pole to exchange mail with the submarine Neptune this summer.”

“What!”

“Quit your kidding.”

“Say it again.”

“You’re dreaming.”

These and a chorus of similar exclamations greeted Andy’s quiet statement. He said it in such a matter-of-fact way that most of the men in the room thought he was joking and he had to repeat his statement two more times before they took him seriously.

“Wait a minute,” he added. “I’ll read you the telegram that came this afternoon.”

He pulled the message from his pocket and read his father’s words. When he had finished they were all grave. There was no question now. They were going to the North pole on their first great test of the new airship. Every man in the room knew something of the dangers of a polar flight and they admired Andy’s father for his courage in sending the Goliath on such a voyage.

“We’ll make a lot of flights to various cities in this country,” explained Andy, “before we start on the long trip north so the ship will have a thorough test and we’ll know just exactly what she’ll do.”

“She’ll do everything the specifications call for and more too,” exclaimed one of the rigging foremen and his words represented the sentiment of every expert in the room for they all had explicit confidence that the Goliath would live up to expectations of her designers and builders.

“When do you think we’ll be ready for the test flights?” one of the helium experts asked Andy.

“With the polar trip definitely decided on,” replied Andy, “we’ll have to be in the air before the end of the next sixty days. That means we can’t afford even a single hour’s delay on the assembly schedule and we may have to lengthen the shifts in order to get through.”

“We’ll work 24 hours a day if we have to,” said one of the enthusiastic foremen, for after nearly two years of exacting construction work, they were all anxious to see the Goliath test its wings.

The remainder of the supper hour was devoted to heated discussions of the various features of the dirigible, and who would be selected for the crew. Every man in the room hoped that he would get by the final weeding out process and win a permanent berth on the world’s largest airship.

Timms was waiting for Andy and Bert after supper in the lobby of the hotel.

“I’m going over and talk to the Rubanian,” he said. “Better come along.”

They were about to leave the lobby when the program of dance music which was coming in on the radio stopped abruptly for a station announcement.

“Wait a minute,” said Bert. “They haven’t stopped for the usual station identification. They cut that piece off in the middle.”

They went closer to the receiver and it seemed as though the announcer in the station miles away had seen their movement for he started his announcement at once.

“We have just received a special bulletin,” said the voice on the ether waves. “A powerful monoplane, of low-winged construction, was sighted just at sunset near Bellevue, Ky. It was flying over a restricted area in violation of department of commerce rules. The machine is fast and slate-gray in color. There appeared to be only one man in the machine and from the description at hand it is evidently of foreign make. It is possible that some European flyer, on a secret long-distance flight, has crossed the Atlantic, and, unaware of the department of commerce regulation, flew over Bellevue, home of the giant airship Goliath. Now, news hounds, get busy and let’s see what you can find out about this strange, low-winged monoplane. Any information should be sent direct to this station. Our program of music will continue.”

The voice stopped and the dance band which was featured at that hour on the air resumed.

“That ought to get results,” said Andy. “Anyone listening in on this program who has heard or seen a plane in the last two hours will undoubtedly send in a report.”

“We’ll have a lot of misinformation,” said Timms, “but a real clue may develop.”

“How many stations carried that announcement?” asked Bert.

“The message was sent to about 50 of the major broadcasters,” replied Timms, “and every one of them will put it on the air.”

“In other words, you covered the whole country,” grinned Bert.

“That’s what I hoped to do,” replied Timms. “Now we’ll see just how much value the radio is to the secret service in an emergency when we need the cooperation of the public.”

“You’ll have something definite before midnight,” predicted Bert, who was quick to rise to the defense of his chosen profession.

“It’s seven-thirty now,” said Andy, glancing at the clock in the lobby. “That gives you four and a half hours.”

“That’s enough,” replied Bert. “If there isn’t some real clue by that time I’ll buy your suppers tomorrow night.”

“And if you win?” Andy asked.

“Then I’ll eat supper tomorrow night and the next on you two,” grinned Bert.

“I’ll buy your suppers for a week,” promised Timms, “if we know by midnight where this mysterious plane went.”

The doctor in charge of the little emergency hospital which was a part of the National Airways equipment at Bellevue informed them that Dubra, or Cliff Bolton as he had been listed on the payroll, was resting easily and in condition to talk.

The Gerka agent was in a private room and a soldier was seated across the hall, facing the door. The windows were barred and there was little chance that Reikoff’s secret agent would go free until Uncle Sam decided he had paid the penalty for his treachery.

Dubra was propped up on pillows, reading an evening paper. He looked up expectantly when they entered but the moment he saw Timms he became sullen. The radio down the hall was plainly audible and Andy recognized the music of the dance band they had heard over the receiving set at the hotel. Unquestionably Dubra had heard the emergency announcement. Andy wondered if there had been any connection between Dubra’s attempt to wreck the hangar that morning and the arrival of the Rubanian plane. It was logical to believe that it was part of a carefully laid out plot. He had thought the Goliath safe from an air attack by a jealous foreign country but if the gray plane they had sighted that afternoon proved to be a Rubanian ship, they would have to station several fast army pursuit ships at the field or perhaps install searchlights to ward off any night attack. Possibilities of destruction of the Goliath by an air attack were limitless and Andy grew sick at the thought that the great ship, which represented the labor and love of hundreds of men, was in danger and he looked at the wounded agent of the Gerka with little sympathy.

“How do you feel tonight?” Timms asked Dubra.

“How do you suppose?” was the sullen reply. “I’ve got two bullet holes in my right leg and another in my left one.”

“You’re lucky you didn’t get one through the heart,” replied Timms cheerfully.

“You’ll suffer for this outrage,” promised Dubra, whose eyes shifted from the secret service agent to Andy, then to Bert, and back to Timms.

“Just as soon as my government learns of this unwarranted attack you’ll be in enough trouble to last you the rest of your life.”

Dubra’s bravado angered Timms, who spoke fiercely.

“Shut up and listen to me,” said the secret service agent. “You’re a Rubanian resident who posed as a naturalized American. You entered this country unlawfully, you’re a secret agent of the Gerka, you attempted to commit murder this morning when you turned on the power of the hangar door and almost killed a half dozen men working on it, you attempted to escape from a military reservation and were shot when you failed to obey repeated commands to halt. A full report of this has been forwarded to the department of justice. You’ll be lucky if you don’t spend the rest of your life behind the bars at a military prison for remember, Dubra, that military, not civil, courts will deal with your offense and army courts are well known for the severity of their sentences on scoundrels such as you.”

The concise, bitter indictment by Timms broke Dubra’s spirit of bravado and the agent of the Gerka cringed as he thought of his black future.

“How much were you to be paid for wrecking the hangar?” asked Timms.

Dubra refused to answer.

“How much?” Timms repeated the question.

Still no answer.

“All right, boys,” said the secret service agent. “We’ll just turn off the light and leave Dubra alone in the dark tonight. He has plenty to think about. Oh, yes, I’ll tell the orderly down the hall Dubra’s to have no water to drink and any calls from this room are not to be answered.”

Timms reached for the light switch and Dubra suddenly changed his mind.

“I’ll talk, I’ll talk,” he cried, “only don’t leave me alone in the dark. Something might happen. What do you want to know?”

“Are you the only agent of the Gerka in the plant now?” asked Timms, his words snapping through the quiet of the room.

“Yes,” replied Dubra so quickly that the others were convinced he had told the truth.

“And your job was to wreck the hangar and delay construction until another and more powerful agent could get here and finish the job of sabotage against the Goliath?” went on Timms.

This time there was no reply to the question and Dubra turned his face toward the wall.

“I’ll give you a minute to make up your mind,” said Timms.

The seconds ticked away and there was no sound from any of the four in the small room.

“Make up your mind,” warned Timms. “Ten more seconds and the lights go out.”

The secret service chief, Andy and Bert turned to leave the room. They were on the threshold when Dubra called them back.

“My job was to wreck the hangar,” he confessed, the words coming slowly and evidently with the greatest reluctance.

“Who is going to attempt to wreck the Goliath?” demanded the secret service chief.

“I don’t know,” whispered Dubra. “The Gerka doesn’t work that way. Each of us is assigned a specific task to carry out independent of anyone else.”

“Then you don’t know who flew that gray monoplane over here this afternoon?” asked Andy.

“I didn’t know a monoplane came over.”

“Don’t lie,” said Timms. “If you didn’t hear the noise you certainly heard the announcement over the radio just a few minutes ago. Did you expect someone to make a long-distance flight from Rubania for the purpose of destroying the Goliath?”

“I didn’t expect anyone,” replied Dubra.

“But someone else was to carry out the attack on the Goliath?” persisted Timms.

“Yes,” whispered Dubra.

“That’s enough for the present,” said Timms. “Let’s go, boys.”

“You promised Dubra some pretty rough treatment if he wouldn’t talk,” said Bert when they left the hospital.

“It was bluff, pure and simple,” smiled Timms, “but he’s in a precarious situation and is smart enough to realize that his case will be handled by a court-martial. He’s between two fires. If he talks too much his own organization, the Gerka, will revenge themselves on him. If he refuses to talk to us, his penalty will be doubly severe.”

“At least the talk with Dubra did one thing,” said Andy gravely. “We know for sure that the Goliath is in grave danger and that the man selected to carry out its destruction has not yet arrived at Bellevue.”