Free The Ghost at Skeleton Rock by Franklin W. Dixon

may be up against a gang of air-freight thieves and smugglers who deal in other things besides isotopes!”
    â€œAny leads so far?” Frank asked.
    â€œJust one. My next job is to keep watch at a freight warehouse near the airport.”
    Joe jumped up from his chair in excitement. “How about Frank and Chet and Tony and myself doing a stakeout at the warehouse?”
    The other boys were equally enthusiastic about the idea, and Mr. Hardy finally agreed. They soon devised a plan. The boys would hide in crates to be carted to the warehouse that evening.
    After dinner the boys started out for a trucking company on a street called Calle Pacheco. The owner of the firm was cooperating with the police on the freight robberies.
    â€œDon’t look now,” said Tony a few minutes later, “but I think a car’s tailing us.”
    Frank leaned forward to watch the taxi’s rear-view mirror. “You’re right,” he muttered. “Maybe we’d better split up.”
    Quickly he arranged with Chet and Tony to stay in the taxi and try to shake off their pursuer. “If you lose him, meet us at the trucking company in half an hour.”
    Three blocks down, the driver stopped for a red light. Quickly the Hardys jumped from the taxi and lost themselves in the passing throng of pedestrians.
    They had not gone far when Frank and Joe noticed that a tall man seemed to be trailing them. His face was almost hidden by the pulled-down brim of his slouch hat. The Hardys were struck by something familiar about the fellow! But there was no time to mull this over.
    â€œBetter shake him,” Frank muttered.
    Joe agreed. Quickly the boys hailed a taxi and resumed their ride to the trucking company. When they arrived, the owner said:
    â€œAh, sí, I have the boxes all prepared. The covers, of course, will not be nailed down.”
    A few minutes later Chet and Tony joined them. The boys took their places in the big crates, which were loaded aboard a truck. Soon they were bumping and rattling through the streets of San Juan.
    When the truck arrived at the warehouse, the boxes were carried inside to the main room. As closing time neared, the workmen’s voices died away and everything became quiet.
    The first half hour of the boys’ vigil went slowly. Cramped and tense in their hiding places, they sweated out each passing moment.
    Then Frank heard a noise!

CHAPTER XI
    Warehouse Marauders
    FRANK strained his ears, wondering if he was mistaken. Then he heard it again—a faint scratchy noise which he could not identify.
    Raising the lid of his box, he beamed a flashlight toward the sound. A large sheet of dirty wrapping paper lay a few yards away. On it crouched a small, brown furry creature.
    â€œWhat gives?” came a whisper from Joe’s box.
    â€œJust a rat.”
    The rodent froze for a few seconds in the glare of light, its beady eyes shining with reflected brilliance. Then it scampered off into a dark hole nearby—apparently the opening to a small tunnel for an electrical conduit, but large enough for a person to crawl into.
    The boys resumed their wait, shifting occasionally to exercise their cramped muscles. The warehouse lay wrapped in gloom, pierced only by a faint glow from the moon through a skylight.
    Some time later another noise broke the stillness. It was a faint curse in Spanish! The voice sounded oddly hollow and muffled.
    Frank and Joe raised the lids of their crates a crack. A moment later they saw two figures wriggle through the tunnel opening. Both snapped on flashlights and played them around the room. Then the intruders, whose faces were in shadow, separated and began examining the shipping labels on the boxes and crates.
    One of the men approached the spot where the Hardys were hiding. The boys closed the lids noiselessly and held their breaths. Through a knot-hole, Joe could make out one man’s legs, scarcely inches away. Apparently he was examining the