“We're not here just for a visit,” Frank announced. “We thought you might help us by giving out some information.”
The young detectives then told the tower chief about their encounter with the low-flying aircraft the night before.
“Were you able to identify the type of aircraft, or get its registration number?” Diamond asked.
“It was too dark for positive identification,” Joe replied. “Anyway, we were both busy ducking!”
Diamond looked thoughtful. “Funny. I know of no private landing fields in that area.” He paused. “There have been several strange things going on in the air around here lately,” he said.
“What kind of strange things?” Frank asked.
“At night we've picked up messages between planes that must be in code. They sure make no sense.”
Suddenly a light flashed on the console and one of the radio speakers crackled to life. It was the unicom frequency used by flight students for practice and by pilots wishing to communicate with one another in the air.
“Bayport tower! This is Highflite One-Four-Alfa!” the pilot identified his craft, using Alfa for A. “How do you read?”
To the boys' astonishment, the tower chief's normally ruddy face turned pale. He picked up a microphone, then stood motionless, apparently unable to speak. Finally, in a quivering voice, he responded:
“High ... Highflite One-Four-Alfa! This is Bayport tower. Reading you loud and clear.”
“This is One-Four-Alfa. Not on an instrument flight plan. We are on top at thirteen thousand. Can you get us cleared for an ILS approach at Bayport?”
“Negative, One-Four-Alfa,” replied the tower chief. “Bayport is now below ILS minimums. Advise you contact Air Traffic Control on the proper frequency.”
There was no answer from the aircraft. Diamond seemed to be under a great strain. He placed the microphone on a table and mopped perspiration from his face.
“What's wrong?” Frank asked anxiously.
“The aircraft that just called! That identification number!” the tower chief said in a shaky voice.
“What about the identification?” Joe urged.
“That's the number of the plane once owned by Stanwide Mining! The one that crashed in the sea several months ago!”
“M-m-m, that surely is strange,” Frank said, frowning.
“I don't know what's going on,” replied the tower chief. “But I'm sure of one thing. The pilot who called sounded exactly like Clint Hill!”
Just then the radio speaker again crackled to life. A weird sound, like a disembodied chuckle, came eerily from it. Then a voice spoke. “The dead can tell no tales!”
“That
is
Clint Hill!” Diamond murmured, looking like a ghost himself.
“What do you make of it?” Frank asked.
“Only one thing,” said Diamond in a frightened voice. “I never used to believe in ghosts. But now I do!”
CHAPTER IV
Police Orders
FRANK and Joe, startled by the unearthly voice, were equally amazed by the tower chief's admission that he believed in ghosts!
“There must be some other explanation,” Frank said.
“Well, maybe. I guess I lost my head for a moment. But there's no way we can check on the aircraft,” Diamond declared. “Our field doesn't have airport surveillance radar, and the pilot said he wasn't on an instrument flight plan, so Air Traffic Control wouldn't have any record on him.”
“You are required to keep a record on tape of all two-way communications between the tower and aircraft, aren't you?” asked Frank.
“Yes,” Diamond replied.
“Could it be arranged for us to borrow a copy of the tape with Hill's voice on it?”
“I'll have to check with our regional office,” said the tower chief. “But in view of the circumstances, I'm sure it will be all right.”
The boys, puzzled by this airport mystery, left the control tower and headed for the terminal building.
“Let's find a telephone and call Mr. Allen,” said Frank. “I want to tell him what happened, and also ask him where we can find Lance Peterson.”
Mr. Allen was astounded at hearing the news about Clint Hill. He was certain that it was someone's gruesome idea of a joke. Frank then asked him if he had heard anything about the strange coded messages that Lou Diamond had mentioned.
“No, I haven't.”
Frank next inquired where he could find Lance Peterson, and was told that he should be in his office at the Stanwide hangar.
The Hardys walked along the north side of the Bayport field until they came to the Stanwide hangar. It was a huge metal and stone structure with a high convex roof. On each side of the building were lean-tos which housed the shops and offices of the company's flight operations. The door to one of these offices was marked CHIEF PILOT.
The Hardys knocked, then opened the door and walked in. Standing near a window was a man of average height, with sandy-colored hair and a hard, weathered face. He turned and stared at the Hardys as they entered.
“Mr. Peterson?” asked Frank.
“That's right,” the man replied. “What can I do for you?”
The boys introduced themselves and announced that they would like to ask him a few questions. Peterson agreed, and appeared quite calm and pleasant until Frank asked him about the crash at sea in which Clint Hill had been lost. Peterson's face paled. He nervously sat down behind his desk and clutched both sides of the chair.
“We crashed, and that's all there is to it!” he snapped. “Let's drop the subject.”
“What was the cause of the crash?” Joe asked.
“The airplane's at the bottom of the ocean,” said the pilot. “There's no way I can check for the reasons.”
“You were in the plane,” Frank countered. “Can't you make a guess?”
“Both engines quit,” Peterson said. “In those circumstances, fuel contamination is the most probable cause.”
“Are you certain Clint Hill is dead?” Joe queried.
“Of course he is!” Peterson answered impatiently. “Why do you ask that?”
“Because his ghost contacted the tower just a little while ago,” Frank announced.
“I'm not in the mood for bad jokes,” shouted the pilot, leaping to his feet. He glanced at his wrist watch. “Anyway, I'm scheduled to fly in a few minutes. I'll have to go.”
The boys left the office, with Peterson trailing close behind them. He pulled the door shut, locked it, then walked off without saying another word.
“What do you make of him?” Joe asked his brother.
“Our questions sure made him uneasy. If you ask me, he's trying to cover up something.”
The young detectives decided to look around the hangar for possible clues to the mystery. They entered by a side door and acted very casual, as if interested only in seeing the aircraft stored there. They had covered nearly half the premises when a young man came strolling out of the pilots' lounge.
“Hey, look!” said Joe. “There's Jerry Madden!”
The young pilot was a wiry, good-looking youth whose brother was a teammate of the Hardys on the school's varsity football squad.
“Hello, Jerry!” called Frank.
Jerry turned. When he saw the boys, who ran to meet him, his face broke into a wide smile.
“Hi! What are you fellows doing out here at our lil ole aerodrome?” he asked with a laugh. “Getting the yen to do some aviating?”
“We'd like nothing better than a short hop in a sightseeing plane,” Frank said with a grin, in an effort to explain their presence without arousing Jerry's curiosity. “But the weather has other ideas. So we decided just to roam around and look at the planes.”
“What are
you
doing here?” Joe asked Jerry.
“I have a job flying for the Stanwide company,” Jerry explained. “I was hired soon after I received my instruments and multiengine ratings last spring.”
As they talked, the boys were not aware that a uniformed policeman was approaching from behind. The officer hailed them.
“What are you fellows doing here?” he demanded.
“I work here, Officer,” Jerry said.
“And who are you two?” the policeman said, eying the Hardys carefully.
“They're Frank andâ” Jerry began.
“Let them speak for themselves,” interrupted the policeman.
“I'm Frank Hardy. This is my brother, Joe. We're going to work for Stanwide.”
“I'll have to see some identification.”
The boys extracted cards from their wallets and handed them to the policeman. He examined the cards, then suddenly became apologetic.
“I know of you and your father by reputation,” he said. “Sorry to have bothered you.”
Suddenly Joe sensed that they were being watched. He glanced to his left, without turning his head, and out of the corner of his eye glimpsed a man's face peering at them from behind an airplane near the entrance. But the face drew back out of sight before Joe could distinguish the features.
“Are you boys here on a case?” the policeman asked.
“We're on vacation. This is a summer job,” Joe replied, speaking more loudly than usual for the benefit of the man behind the plane. “We were just looking at the company's airplanes.” He nudged Frank to agree.
“What seems to be the trouble, Officer?” Jerry questioned.
“Our desk sergeant received a call saying that two prowlers had been seen in this hangar,” the policeman explained.
“Do you know who made the call?” Frank asked.
“No, it was anonymous.”
Joe glanced in the direction where he had seen the face. It did not reappear. He motioned Frank to keep talking, then darted to where he had spotted the eavesdropper. No one was there.
The young detective quietly moved in the direction he thought the stranger must have taken. Joe found it awkward trying to maneuver, unseen, around the closely packed aircraft. Suddenly he spotted a stocky man in mechanic's clothes walking quickly toward Lance Peterson's office. Joe hid behind the tail section of an aircraft and watched. Upon reaching Peterson's door, the mechanic anxiously jiggled the knob. Finding it locked, he walked away and out of sight.
Joe returned to Frank and the others. He apologized for going off so abruptly. “Thought I saw one of the real prowlers, but I must have been mistaken.”
“How many mechanics do you have working here, Jerry?” Frank asked.
“Eight,” he answered. “But there's only one on duty in the hangar todayâMike Zimm. Why do you ask?”
“Oh, I'm just curious,” Frank said nonchalantly. “Joe, it's time we started for home.”
The boys, accompanied by Jerry and the policeman, walked toward the door of the hangar. As they neared it, Frank and Joe noticed something that brought them to a stop. On the floor lay a splintered section of wooden board.
The boys thought it strange that a piece of debris like that should be left on a floor so spotlessly clean.
Apparently the policeman thought so too. He bent down and picked up the board. Under it was a set of footprints, embedded deeply in the concrete.
“I wonder whose they are,” said Frank.
Jerry Madden moved closer and gazed down at the floor.
“I know whose footprints they are,” he said. “Clint Hill's.”
CHAPTER V
Warehouse Crash
“CLINT Hill's footprints!” Joe exclaimed. “How do you know, Jerry?”
“The head of our company, Mr. Allen, was very fond of Clint,” the pilot explained. “Shortly before he was lost in a crash at sea, the hangar floor was resurfaced with new concrete. Mr. Allen, perhaps partly in fun, asked Clint to make the prints. I wasn't here at the time, but it's a well-known story around the flight department.”
The Hardys studied the footprints carefully. They noticed that the instep of the right foot was narrower than that of the left.
The policeman, who had to get back to his regular duties, said good-by. Jerry watched his young detective friends as they continued their study of the prints.
“I saw something just before I met you fellows that perhaps I should tell you,” he said.
“What's that?” Frank asked.
“A man's arm reached in through the door and placed that board over the prints,” Jerry explained.
“That's funny,” Frank commented.
Jerry went on, “I didn't attach any importance to it at the time. In fact, I'd forgotten about it until I saw how interested you were in those prints. Maybe the person is still around.”
The boys dashed outside the hangar, but saw no one.
“We've heard of Clint Hill a couple of times today,” Joe told Jerry, but did not explain further.
After requesting Jerry to keep his eyes open and report to the Hardys any unusual goings-on around the hangar, the brothers left for home. Both were quiet, pondering over all that had happened during their visit to the hangar. Why had Hill's footprints been covered? Was it to make certain the boys would not see them? And who had reported the presence of two prowlers to the police? Then there was the mechanic, Mike Zimm. Had he been the man who had eavesdropped on their conversation? The case, the boys agreed, was becoming even more puzzling.
During supper they related their day's adventure to the family.
“Mighty queer business,” Aunt Gertrude commented. “You boys had better watch your step. I don't know what we're coming to when a company's employees can't walk around its private hangar without someone setting the police on them!”