The Great Airport Mystery by Franklin W. Dixon

agreed. “Incidentally, I’ve learned that tract of land is part of an abandoned farm, but the whereabouts of the owner is not known.”
    The boys discussed their plan to explore the area by helicopter. Their father approved, and suggested that they ask Randy Watson to make arrangements for hiring a craft and pilot.
    Frank was about to make the call when the telephone rang. He picked it up. An eerie voice at the other end said, “Is this the Hardys’ house?”
    â€œHi, Chet!” Frank said with a chuckle. His friend was imitating Clint Hill’s voice.
    But as the unearthly voice continued, Frank realized it was not Chet‘s! The words it spoke turned his blood cold.
    â€œThis is not Chet,” intoned the speaker. “This is the ghost of Clint Hill. Where is Lance Peter· son?”

CHAPTER XIII
    The Tornado
    CHILLS ran up and down Frank’s spine and he stood motionless. He was about to answer that he did not know the whereabouts of Peterson, but then his momentary fright left him and he changed his mind. Frank decided to question the mysterious caller and perhaps get a lead as to his identity.
    â€œI’ll make a bargain with you,” the young sleuth proposed.
    â€œWhat kind of bargain?” asked the voice, still in an eerie tone.
    â€œI’ll give you some information about Peterson,” said Frank, “if you’ll tell me who you really are.”
    There was a long pause.
    â€œForget it!” said the sepulchral voice. “I’ll find that double-crosser myself!”
    â€œWait!” Frank urged. “Don’t hang up!”
    But a sharp clicking sound brought the conversation to an abrupt end. Disappointed, Frank shrugged, then dialed and made arrangements to rent a helicopter. In a few minutes he rejoined his family. They discussed the weird call from the “ghost.”
    Mrs. Hardy looked distressed, while Aunt Gertrude expressed contempt. “These people who play tricks on the telephone!”
    â€œYou say that this person called Lance Peterson a double-crosser?” Mr. Hardy asked.
    â€œThat’s right, Dad,” Frank answered. “I wonder if our ‘ghost’ actually is in cahoots with Peterson and Lieber, and was supposed to go with them aboard the plane, then found they’d suddenly left without him.”
    Father and sons continued to discuss this new development and its connection with the case, but failed to arrive at any conclusion. Presently Randy Watson telephoned and said he had made arrangements for Frank and Joe to fly in a helicopter the following morning. A minute later Mr. Allen called to tell the boys that authorities in the United States, Canada, and Mexico had been alerted to look for the missing company plane.
    â€œAs yet nothing has been reported,” he said.
    The next day Frank and Joe went to Bayport Airport. As they walked onto the parking ramp of Ace Air Service, Randy met the brothers and introduced them to Mack Carney, their pilot, young and well-built. A short distance away stood a small, three-place helicopter. Its cockpit was enclosed in a fishbowl-shaped Plexiglas canopy.
    As the boys walked toward the craft, they glanced at the sky and noticed that a cloud cover was developing. Conditions to the south and southwest appeared especially bad. There, the bases of some clouds were darkening to an almost bluish black.
    â€œLooks like a storm,” Joe commented. He feared that their flight might be delayed because of weather.
    â€œThere shouldn’t be any problem,” Mack reassured him. “I’ve already checked the forecast. Ceilings and visibility are not expected to drop below visual flight rules at any time.”
    He told the Hardys that scattered thunder-storms were predicted for the area, but that these could easily be avoided. By midafternoon the weather system was expected to move out to sea, with rapid clearing behind it.
    Minutes later, the helicopter was