The Mystery of the Spiral Bridge by Franklin W. Dixon

“oof.”
    Startled, the other boys’ companions wheeled around to face the Ping-Pong table. It lay flat on the floor, with hapless Chet sprawled out across it. Red-faced, as the others roared with laughter, he picked himself up.
    â€œWhat happened?” Tony asked.
    â€œI fooled him with a spin shot,” Biff said. “Good old Chet leaned over too far and that did it.”
    Frank found that except for one splintered leg, no damage had been done to the table.
    Joe and Tony quickly got tools from a workbench and repaired the table leg.
    â€œOkay, fellows,” Frank said finally. “Before Chet has any more accidents, let’s get down to business.”
    First, Tony took the precaution of posting his German shepherd dog outside the basement door.
    â€œAxel will warn us if anybody comes snooping around,” he said.
    The boys seated themselves in a partitioned-off den-study, and Frank opened the discussion.
    â€œJoe and I will lay our cards on the table. We’ve met with nothing but setbacks ever since we took over Dad’s case.
    â€œYou’re not giving up?” Tony Prito put in quickly.
    â€œOf course not!” Joe assured him. “There’s no mystery that can’t be solved, if it’s worked on long and hard enough.”
    â€œRight,” Chet Morton said sagely. “You two should know.”
    Phil Cohen winked at Biff. “A hunch tells me you Hardys got us together to decide on a plan of action.”
    Frank smiled. “You’re right, Phil. You fellows have always stuck with us when the going got rough.”
    Chet Morton nodded vigorously. “What else are pals for?”
    â€œI’m glad to hear that,” Joe said, “because now we come to the heart of the matter.”
    The Hardys were silent for a moment as Frank looked from face to face. “Joe and I,” he said, in measured words, “are asking each of you to join us on a dangerous mission.”
    Chet’s eyebrows arched like the trajectory of a soaring shot. “Dangerous? Where?”
    â€œKentucky.”
    The Hardys’ friends exchanged excited glances.
    â€œYes,” Joe said, “let’s go to Kentucky and find out more about that sabotaged bridge and who dry-gulched Dad.”
    The Hardys thoroughly briefed the others on their sleuthing so far, including the New York trip. They had just concluded when Tony’s dog began barking.
    â€œSomething’s going on!” said Tony. He dashed to the basement door, opened it, and peered into the darkness.
    The big German shepherd was leaping up at the shadowy figure of a man near the basement window!

CHAPTER IX
    Fake Names
    â€œDOWN, Axel!” A deep voice came from out of the darkness, followed by a happy whimper from, the German shepherd.
    â€œIt’s my father!” Tony exclaimed.
    A sturdy-looking man, the dog bounding at his heels, stepped into the basement.
    â€œHello, Mr. Prito.” Joe grinned. “For a minute we thought you were a prowler.
    The broad-shouldered contractor’s face, ruddy from years of outdoor work, creased in a smile,
    â€œNot guilty. When I saw all those cars parked in the driveway, I thought maybe a political rally was in progress here.”
    â€œFrank Hardy for mayor,” Phil quipped.
    Everyone laughed, then sobered as Frank spoke up. “We were having a powwow about your road job, Mr. Prito.”
    The group adjourned to the den, where the contractor pulled up a chair and sat down wearily.
    â€œI’m afraid we are licked.”
    â€œDid something else go wrong, Dad?” Tony asked.
    â€œMy men started to repair the bridge, and it collapsed again. This time we found an acetylene torch was used to cut through the stress points of the girders. The cuts were covered with a putty filler and painted over to resemble rivets—so of course no one noticed anything wrong until the structure gave way.”
    â€œWas anyone