The Bombay Boomerang by Franklin W. Dixon

give a yell!”
    â€œAnd don’t let the spooks get you,” one policeman said with a grin.
    â€œIt’s spooky all right,” Frank muttered as they set out.
    In the moonlit graveyard leaves rustled in the wind. Tombstones cast eerie shadows. Off in the distance a dog howled.
    Frank and Joe began working down from the northwest corner where the Poe monument stood, stepping carefully around the graves as they searched.
    A cloud scudded across the face of the moon, leaving the cemetery in darkness. The boys waited for the brightness to return. To while away the time, Frank asked in an undertone, “Which of Poe’s characters does this situation remind you of?”
    â€œThe black cat.” Joe grimaced.
    The cloud swept past. They resumed their search under the light of the moon. “What’s that?” Frank pointed to an object, shaped like a milk bottle, near a large mausoleum.
    â€œA mercury flask!”
    They hastened around behind the mausoleum and found a pile of containers, heaped up as if they had been thrown there in a hurry.
    Frank picked one up. “Hey, Joe! This sure doesn’t weigh a hundred and thirty-five pounds. In fact, it’s empty!”
    Joe examined a number of others and whistled softly. “So are they all. The mercury is gone!”

CHAPTER XIII
    Aboard the Indian Freighter
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    JoE held one of the flasks upside down and waited to see if any last drops of mercury would drip out. None did. He tried the same experiment on several more containers with the same negative results.
    â€œIf it had been a quick-change operation and the thieves had poured the mercury into their own containers, we’d be almost certain to find a trace in each flask. Yet these are all bone-dry.”
    â€œOf course they are. They were empty to begin with,” Frank said, “which helps us to fit together two pieces of this jigsaw puzzle. First, we heard one of the gang mention ‘heisting the empties.’ That makes sense now. And second, the footprints at the Precious Metals loading yard were too shallow for men carrying one-hundred-and-thirty-five-pound flasks. Now we know why. There was no mercury in them.”
    â€œIt must have been stolen earlier,” Joe agreed. “Probably on the dock where the cargo was landed, or maybe aboard ship. The empty flasks might have been taken to throw us off the track.”
    â€œSo,” Frank said, “it’s just as well we have an appointment with an Indian freighter. Right now we’d better tell Captain Stein of our discovery. And we’ll call Dad early tomorrow morning.”
    The police investigated the place where the flasks had been discarded. After that, they drove Frank and Joe to a hotel, where the boys took a room for the night. Next morning they telephoned their father through a Bayport neighbor, since they were afraid their own phone was still being tapped. Mr. Hardy was puzzled by the empty mercury flasks. He said he would query other companies that handled mercury and call back.
    An hour later the boys were still batting the mystery back and forth when the phone rang. Their father said that several companies reported finding empty mercury flasks. “They’re baffled about the method used by this gang. You could be right in suspecting thievery on the dock or the ships. See what you can find out aboard the Nanda Kailash and keep your eyes open for any connection between the disappearing mercury and the Bombay Boomerang, Frank!”
    â€œOkay, Dad. We’ll go to the ship right away.”
    Frank and Joe took a taxi to the harbor. They drove along a narrow street lined by large warehouses and heavy trucks to an open area dominated by the Indian freighter tied up at the dock. She was painted black, with a white band high above the waterline amidships. Derricks, slings, and lifts rose over the hold from which the cargo was being unloaded. The stern, riding high out of