the return flight to bellevue was uneventful and the monoplane settled down beside the goliath’s hangar shortly after noon. andy taxied the plane up to the apron and they piled out and hurried into the main hangar to see what progress had been made on the goliath since their departure.

even in the short time they had been away the crews had put on the finishing touches. the great silver hull gleamed in the softened light of the hangar. the main gondola had been completed, the observation cockpits on top of the big bag were in place and hundreds of helium tanks were piled along the walls of the hangar—empty. that meant that the gas cells had been filled with the precious gas. the goliath was almost ready to take the air.

charles high and captain harkins hurried up to them.

“how does the goliath look today?” andy’s father asked.

“wonderful, dad, simply wonderful,” replied andy. “when will you make the first test?”

“we may walk it out of the hangar tomorrow but we won’t make a real flight for several days,” replied the vice president in charge of operations for the national airways. “the army has a finger in the pie and when we actually take the air several members of the general staff and a dozen air corps experts will want to be aboard to see if it behaves to specifications.”

“i’m sure it will,” put in blatz. “i’ve seen a good many of doctor eckener’s ships at friedrichshafen and with all due respect to the herr doctor, the goliath is the finest, most carefully designed and built aircraft i have ever seen.”

“that’s a real compliment,” chuckled bert. “it isn’t very often a european will concede superiority to an american in anything.”

“blatz is right,” said captain harkins quietly. “there is no question about the goliath being the finest airship ever built. i expect it to live up to our every hope in its performance in the air.”

“we were surprised when gilbert mathews informed harry of the advance in sailing plans,” andy told his father.

“i was a trifle surprised, too,” admitted the vice president of national airways. “mathews wired me the same day of the change in plans and i replied that the goliath would be able to advance its air tests and keep the date to meet him at the pole even with the earlier sailing. i can’t blame him, though, for wanting to take advantage of the favorable ice conditions which are reported in the north now.”

“the neptune is a great submarine,” said bert, “as far as subs go but i’ll take an airplane or dirigible any day. being shut up in one of those things is like sailing around in a tub. i wouldn’t trade my radio cubby on the goliath for a dozen jobs on the neptune.”

“someone had to go on the neptune and we’ll give harry plenty of credit for his nerve,” said andy. “will you be able to pick up his message tonight?”

“i promised him i’d tune in every night at eight,” replied bert. “we ought to hear him plainly.”

captain harkins asked andy to accompany him to the main office to check over the final construction reports on the goliath while andy’s father took blatz on an inspection trip over the big bag. they entered the luxuriously furnished gondola with its lounge and radio room, the dining salon and the glass enclosed promenade. then to the upper deck of the gondola where the passenger cabins were located. the interior finish was in a cool, pleasing gray, a favorable contrast to the silver of the metalized hull.

after leaving the gondola, they walked down the main runway which was built lengthwise down the middle of the goliath. in the earlier dirigibles this had been little more than a catwalk and none too safe. a plunge off would have meant crashing through the outer fabric and a fall to earth. in the goliath the main runway was a substantial affair six feet wide. made of duralumin, it was strong but light and guard rails proved ample protection for members of the crew or passengers who might be permitted to view the interior of the big airship.

the gas bags were inflated with, helium and held rigidly in place, six of them in the forward part of the ship and six of them in the after section. the transverse rings built of girders of duralumin separated each bag and there was a narrow catwalk between each large gas cell to facilitate the stopping of any possible leaks.

the motor gondolas were built inside the hull with the flexible propeller shafts sticking through the side. there were six of the motor gondolas on each side and each car was carefully insulated so that fire could be confined to one section of the dirigible.

the mid-section of the goliath was forbidden ground to blatz for it was here that space had been provided for the storing of airplanes in time of war. a special device which hooked onto the planes while they were in flight and lifted them into the hold in the center of the airship had been perfected by captain harkins and blatz was anxious to see this. he was in for a disappointment that afternoon for charles high did not take him back that far. instead, they stopped at the fourth transverse girder where a stairway led to the top of the dirigible. there were six of these stairs all told, each running to the top and giving access to the observation cockpits. there was a runway on top of the goliath with strong cables stretched along the side but it would be almost worth a man’s life to attempt to walk on it while the dirigible was in motion and especially if the air happened to be the least bit rough. a fine place, thought blatz, for anyone who was inclined to be seasick.

they walked along the outer runway toward the rear of the goliath and from this elevation blatz had a real opportunity to realize the size of the new king of the air—the craft which reikoff had termed an “air monster.” when they reached the after part of the dirigible with its great fin and elevators, they descended into the interior. motor crews were busy tuning up the engines and the air was filled with the tenseness of preparation.

at dinner that night captain harkins announced that he had received word from the army air corps that the officers who would report on the trial flights of the goliath would be at bellevue before noon the next day.

“that means we’ll walk the goliath out at one o’clock if the wind and weather are favorable.”

the words came to blatz through a daze. he had seen andy and merritt timms of the secret service conferring before dinner and from the look timms had shot his way he knew that he had been the object of their discussion. the goliath would be out of its hangar tomorrow. army officers would arrive and from then on there would be little opportunity to damage the big ship. tonight was the time! even though andy might be suspicious, he would hardly believe him capable of so daring an attempt on the goliath. blatz set his jaw firmly. it was going to be a task he did not fancy for his love for the goliath had grown until he quailed at the thought of its destruction. but he was a rubanian, a member of the gerka. he could not escape from his duty.

andy found an item of interest in the evening paper which he showed blatz. it was another bulletin from rubania. revolution was threatening. reikoff’s power was tottering.

blatz read it eagerly. perhaps he would not be forced to destroy the goliath after all. if he could only wait a few more days. but the one big opportunity was at hand. tonight was the logical one for his task.

andy noticed the european’s hands shook as he read the item, but blatz’s face showed no change of emotion.

“come on, you two,” called bert. “let’s get over to my radio shack and we’ll see if we can pick up harry somewhere off long island in his tin fish.”

it was nearly eight o’clock when they reached the radio shack just outside the main hangar and it took bert some time to time up his apparatus. he plugged in on the main transmitter and a minute later turned around with a grin.

“harry is burning up the air,” chuckled bert. “i was late coming in and wants to know what i’d been doing. accuses me of over-eating. imagine.”

the stream of dots and dashes which had been flickering through the air ceased.

“we’re going to try the radiophone now,” explained bert, “and we’ll be able to talk back and forth.”

when bert completed the proper adjustments andy almost fell out of his chair as harry’s voice echoed in the little room.

“hello bert. hello andy,” said harry, eight hundred miles away and under water in the radio room of the neptune. “tell blatz hello, too, if he’s with you,” added harry.

“the three of us are in the radio shack,” replied bert, “and i resent your implication that i overate tonight. i over-talked.”

“which is just as bad,” came back the voice over the ether waves.

andy picked up the microphone and spoke to harry.

“how is the trip going?” he asked, “and where are you?”

“we’re about 130 miles out of new york harbor,” replied harry. “the sea is a little choppy but nothing to write home about. everything is running smoothly so far and we ought to put in at plymouth in about 12 days.”

“how’s the air in your tin fish?” bert wanted to know.

“fine,” replied harry. “the main hatch has been open all of the time and i haven’t a thing to complain about. i’ll have to sign off now and send some messages for mr. mathews. i’ll buzz you again at eight in the morning.”

“be sure you make it at eight o’clock our time,” warned bert as he signed off.

bert had some work to do on his reserve radio equipment and andy went to his own office to look over the correspondence which had accumulated during his absence in new york.

blatz, professing to be tired after the flight down from new york, said he would go to the hotel and retire early. andy watched until the german civilian observer bad crossed the track and was well on his way to the hotel. he had told timms of his experience in new york but the secret service man was still inclined not to doubt blatz’s right to be at bellevue. whatever watching of the observer was done would have to be by andy.

the assistant pilot of the goliath was busy half an hour reading and sorting the mail. it was unusually quiet around the hangar that night so the scuffing of something against a stick caught andy’s attention. someone was walking cautiously toward the hangar!

andy remained in his chair, fingering through the pile of letters before him. the guarded sound came again. at the end of a minute he turned out the light and slipped out of his office. a small door which led into the main hangar was open.

andy returned to his office to get his flashlight. remembering that he had left it at the hotel, he found some matches beside a half dozen red lanterns which were used to mark danger places on the field. since the goliath used helium there was no danger of an explosion from striking a match in the hangar or, for that matter, aboard the goliath itself.

the assistant pilot of the dirigible stepped quickly through the door and paused to accustom his eyes to the heavy darkness of the interior. he slipped off his shoes and then moved slowly toward the lighter outline of the silvered hull of the goliath.

andy paused. someone was moving slowly just ahead of him. the young airman groped his way ahead, hands outstretched. the next second he was clutching someone’s coat.

they came to grips, but only for a second. the unknown invader of the hangar slipped out of his coat and andy heard him running out of the hangar.

muttering to himself in disgust, andy stooped to strike a match and look at the coat he had seized. as he struck a match, he slipped and stumbled headlong. the match dropped into a chunk of oily waste. it flared and burst into flame but andy remained motionless on the floor, his head resting against a heavy wood block it had struck.

the fire in the waste glowed brightly and leaped higher as it fed on the oil which saturated the waste. unless help reached andy soon the fire would spread to other parts of the hangar and the goliath itself would be in danger of destruction!