The Great Airport Mystery by Franklin W. Dixon Page A

this emblem here,” the executive said. “This was his personal airplane.”
    The boys did not speak, noting that Mr. Allen’s face expressed deep sadness. Slowly walking around the plane, he stopped at the cockpit door, opened it, then climbed inside. He sat there quietly, as if expecting the lost pilot suddenly to appear.

CHAPTER XVI
    Telltale Initials
    GLANCING at each other, the Hardys kept silent as Mr. Allen continued to stare sorrowfully into space. They were eager to ask him more about Clint Hill’s plane, but out of respect did not disturb him. He sat quietly in the cockpit for several minutes, then finally climbed out.
    â€œI assume the airplane was sold after Hill’s accident,” Frank said. “Who bought it?”
    â€œIt wasn’t sold to anyone,” Mr. Allen replied. “The plane was stolen soon after Clint crashed.”
    â€œStolen!” the boys cried out.
    â€œYes,” Mr. Allen answered. “I had almost forgotten the incident.”
    He went on to explain that local and government authorities had investigated the theft, but had turned up nothing.
    â€œWe finally came to the conclusion,” Mr. Allen said, “that whoever stole the plane either crashed in it, or shipped it out of the country.”
    â€œMaybe Hill’s ghost stole it,” Joe muttered derisively.
    Then another angle occurred to the boys. If Clint Hill had survived the crash at sea and was involved in the platinum racket, had he come back to steal his own airplane for use in the thefts?
    Returning to the business at hand, Frank and Joe, aided by Mr. Allen and two troopers, dragged some of the boxes from the cave and the task of loading the stolen material aboard the police helicopter was begun. When the craft was packed to capacity, its pilot quickly departed for the trip back to Stanwide.
    Meanwhile, Joe had hurried off to get Mack and his helicopter. Soon the craft arrived, landing on the pasture near the cave entrance. The pilot jumped out and went into the thieves’ hideout to pick up more boxes for loading. As they emerged from the cave, an eerie, disembodied sound brought them to a stop. Someone unseen was whistling “High Journey.” Mr. Allen’s face turned ash white.
    The whistling stopped. It was followed by a ghostly sounding voice. “You can’t escape from a man you’ve killed!”
    â€œThat’s Clint Hill’s voice!” Mr. Allen gasped. He was trembling.
    â€œWhere is it coming from?” Joe asked.
    â€œListen!” Frank ordered as the whistling began again. He made an effort to determine its source. Suddenly Frank, followed by his brother, broke into a fast run toward the helicopter. They reached the craft just as the whistling ceased.
    â€œIt’s coming from the radio receiver!” Frank shouted in amazement.
    â€œWhat’s going on around here?” asked Mack, completely baffled.
    â€œI wish we knew,” Frank responded, staring at the receiver.
    Mr. Allen now joined the boys and Mack. “If I wasn’t so sure that it was Clint Hill’s voice we heard, I’d say the whole thing is a hoax,” said Mr. Allen with a grimace.
    â€œI don’t believe it’s just a hoax,” Frank assured him. “And now shouldn’t we start loading the boxes aboard?” he suggested, hoping to take Mr. Allen’s mind off Hill’s ghostly message.
    The work was arduous, but soon the helicopter was filled to capacity, reserving enough space so that Mr. Allen could return to Stanwide with his property. The Hardys asked Mack to pick them up later.
    â€œWhile we’re waiting, we’ll do more sleuthing in this area.”
    When all the cargo was secured, Mr. Allen shook hands with the boys, thanked them again, and boarded the helicopter. The pilot started the engine and set the rotor blades at a high RPM for take-off power. The craft lifted off the ground, then headed on a course to