On leaving the hospital after questioning the agent of the Gerka, Andy, Bert and the secret service chief walked over to Andy’s office. There they discussed plans for additional precautions in the guarding of the Goliath.

“I’m convinced now,” said Andy, “that the plane we sighted this afternoon was a Rubanian ship. Either the pilot had made a non-stop flight across the Atlantic or he stopped at some remote place where there was little chance that news of his landing would spread, took on additional fuel, and continued here.”

“The fact that we were up sky-larking may have prevented a bomb attack on the Goliath,” said Bert.

“That’s possible,” conceded Timms, “but I doubt that Rubania would dare to use such an open and violent method. An air attack would mean war with popular sentiment of the world with the United States.”

“A more likely explanation,” said Andy, “is that the agent who is to carry on the actual campaign of destruction against the Goliath arrived in the plane we sighted.”

“I’m inclined to believe as you do,” Timms told Andy. “Our first step, after doubling the guards around Bellevue, will be to trace this strange craft. I’m hopeful that the radio appeal will bring results.”

“I know it will,” said Bert confidently.

“Dad will be back within a day or two,” said Andy, “and I’ll be mighty glad to turn the responsibility of this whole affair over to him. When he’s back on the job, we’ll take a whirl at finding this unknown agent of the Rubanian Gerka who is to destroy the Goliath,” he told Bert.

Timms was busy with a long-distance call to the department of justice in Washington, informing his chief there of the latest development at Bellevue. When he finished, he turned to talk with Andy and Bert.

“Half a dozen army pursuit planes, fully equipped for combat, will drop down here tomorrow morning,” he said. “They’ll remain until the Goliath is ready to take the air and after that at least two of them will accompany the big ship on all of its trial flights. In addition, an anti-aircraft battery with complete night lighting equipment will arrive before sundown tomorrow.”

“That ought to insure us against the success of any attack from the air,” said Andy.

“From the air, yes,” conceded Timms, “but our danger will lie from an attack within. Everyone who comes on the reservation from now on will be doubly checked.”

By ten o’clock that night every possible precaution to safeguard the Goliath had been taken. The military guard around the grounds of the National Airways reservation had been doubled, and extra watchmen had been placed at the hangar. It didn’t seem humanly possible for anyone to get within the lines without discovery.

Descriptions of the mysterious plane had been broadcast hourly from the principal radio stations and a mass of information had been received, telegrams having been relayed from the radio stations to which they had been sent.

These messages were checked, one by one, against the large map which had been hung on one wall of Andy’s office. On this map had been worked out the probable course of the strange plane. It had come out of the northeast, swung over the home of the Goliath, and then darted away in a southeasterly direction, heading toward the mountains.

Telegrams which failed to indicate a plane in this general line of flight were consigned to the wastebasket. The few that might furnish information were studied carefully but in a majority of cases the description of the plane which the sender of the message had seen failed to come close to that of the machine they sought.

Timms found several messages which appeared worth telephone calls to the senders but on each occasion he was doomed to disappointment.

“I thought you said we’d have some definite news before midnight,” he told Bert.

“There’s nearly two more hours,” replied the radio operator hopefully. “I won’t concede defeat until the last minute.”

Timms snorted and turned to another handful of telegrams that had just been forwarded. He was half-way through the pile when an exclamation brought Andy and Bert to his side.

“Read that,” said the secret service agent, tossing a yellow sheet to them.

The message had been sent from Alden, a small town in the mountains of southeast Kentucky.

“Plane crashed near here early tonight. Description appears to tally with that broadcast. From wreckage it must have been a low-winged monoplane, painted gray. No trace found of pilot.” The message was signed by Frank Hacke, editor, the Alden Advocate.

“Who said the radio wouldn’t bring results?” demanded Bert. “This message looks like a real tip.”

“It does,” agreed Timms, reaching for the phone and placing a long distance call for the editor of the Alden paper.

Half an hour elapsed before the operator was able to get the call through and Timms fumed with impatience. When the wire was finally cleared for his conversation, he fairly leaped at the telephone. Question after question was fired over the wire and Andy and Bert, from the very tenseness of Timms’ attitude, knew that the secret service man was getting valuable information. His final words were highly significant.

“I’ll be there as soon as possible. If I can fly in, have auto lights turned on to mark the boundaries of a field that is safe for a landing.”

Timms banged the receiver on the hook and turned to Andy and Bert.

“We’ve found the wreckage of the gray plane,” he said. “It smacked into the side of a mountain about three miles from Alden. The editor of the paper was one of the first ones to reach the scene but they were unable to find any trace of the pilot. We’ve got to get to Alden at once for we mustn’t let that flyer get away. He’s the man who is slated to bring about the actual destruction of the Goliath.”

The words rang through Andy’s head. The pilot had somehow escaped in the crash. It was possible to crack up a ship without injury but it was more likely that the man they sought had jumped while the plane was in flight, drifting down in his chute and leaving the plane to crash to its own destruction.

Andy heard Timms asking if he could fly him to Alden that night. He replied almost mechanically and then hastened out of the office and down the field to rout out several mechanics, who rolled his red sportster out on the concrete apron and checked it thoroughly. The motor sent echoes blasting through the stillness of the night as Andy himself tested it.

He was joined several minutes later by Bert and the secret service agent.

Timms climbed into the forward cockpit and Bert started to crowd in with him.

“Sorry, Bert,” called Andy. “You’ll have to stay on the ground this trip. The Ace is only a two-place job and I can’t afford to overtax its capacity tonight. I’ll need all my speed and climbing ability in dodging over the mountains.”

Bert was keenly disappointed but he knew the truth of Andy’s words and he dropped back to the ground.

“I’ll warn Alden that you’re coming by air,” he said, “and they’ll be sure to have a field marked in some way.”

“Fine,” yelled Andy. “See you tomorrow.”

Flame licked around the exhaust vent of the motor as Andy opened the throttle. The Ace came to life with a quick flirt of its tail. The riding lights gleamed sharply in the night; then were swallowed in the haze of dirt swept up from the field by the wash of the propeller.

Alden was just a little under an hour of fast flying from Bellevue and Andy opened the Ace up until they were skimming through the half clear night at a hundred and twenty miles an hour. The lights of Bellevue disappeared as if blotted out by the hand of an unseen giant and they were alone in the sky.

Andy had plotted a compass course and he followed it closely for Alden was tucked away in the mountains and he could easily miss the village if slightly off course.

By the end of the first half hour the clouds had cleared and a thin moon tried vainly to dissipate the blackness of the night. Lights on the ground were few and far between with midnight almost at hand. The air was raw and Andy snuggled deeper into the sheepskin he had donned for the trip. He checked the time and compass again. Alden should show on the horizon any moment if his calculations were correct. Another two minutes passed and he sighted a glow of light to the left. He nosed the Ace over and dropped lower.

Lights below flashed on and off. He blinked his riding lights and those on the ground answered. There was no way of detecting the direction of the light wind and Andy had to take a chance that there were no bad ground currents. He skimmed over the field to determine its length. It appeared to be on a side-hill for level stretches of land were few and far between in that section of the state. The field was long enough for an easy landing and he cut the motor and slid down the invisible trail.

He was going in too fast and he opened the throttle and zoomed into the sky for another try. The second time he stalled all the way down, drifted over the top of the car whose lights marked the near end of the field, and dropped to an easy landing. He swung the Ace around and taxied back over the uneven field. A group was waiting when they climbed down from the cockpits.

Fred Hacke, the editor, stepped up and introduced himself. With him was Sheriff Jud Barnes, a six foot two man of the mountains who was proud of his great, booming voice.

“Get in my car,” said the sheriff, “and I’ll run you over to the hill where that airplane busted.”

For half an hour they bounced over a rough mountain road and were glad enough when the sheriff stopped the car and led the way through a patch of timber. The grade was steep and they were compelled to rest several times. Finally they came to a small clearing, crossed this and just beyond saw a darker mass against the trees. The sheriff turned his flashlight on a tangled pile of cloth and metal, the broken remnants of the machine Andy had chased only a few hours before.

The editor and his party came up and they made a thorough inspection of the wreckage. Motor numbers and the name of the maker had been filed away, the plates on the fuselage had been removed and every means of absolute identification taken off. In spite of this Andy and the secret service agent were positive that the plane was of Rubanian make and that an agent of the Gerka had been at the controls when it had been sighted at Bellevue.

“We haven’t found the flyer yet,” said the sheriff. “Maybe he spilled out somewhere before the wreck. We’ll search the hills in the morning.”

“I don’t think it will do any good,” replied Andy. “The chap that was flying this machine undoubtedly took to his parachute. He may have landed some miles away. If the controls were locked before he jumped, the ship could have cruised alone for three or four minutes on a quiet night like this.”

“We’ll have a look anyway,” said the sheriff, and Andy and Timms decided to remain at least until noon to see if the searching parties discovered anything of importance.

They returned to Alden, took a room at the hotel, and slept until dawn. Andy went out to the field where they had landed and went over the Ace carefully while Timms accompanied the sheriff into the hills.

The secret service agent returned at noon and announced that the search had proved fruitless. There were no more clues, either at the scene of the wreck or in the nearby hills, and they decided to return to Bellevue at once.

Andy got the Ace off the improvised airport without trouble and they headed for home through the bright rays of the spring sun. As they sped over the tree-covered hills, Andy flew mechanically, his mind busy on the new problem which confronted them. There was no question now. The Goliath was in serious danger and every means at their command must be used to protect the great airship, destruction of which would mean the ruin of the National Airways, which had invested millions in its construction. But more than the mere financial loss which it would mean was the month of labor by the loyal crew, the years of planning on the part of his father and Captain Harkins, and his own love for the great craft.

An attack from the air was improbable for the Rubanian agent had wrecked his own plane deliberately. Whatever happened would be caused by someone who had easy access to the hangar and Andy resolved that he would be doubly vigilant in the days to come.