Terror at High Tide by Franklin W. Dixon

Bits
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    â€œAlicia! What are you doing here?” Joe cried.
    â€œI’m so glad you guys found me,” Alicia said as she pulled away from Joe. “I would have been trapped in there all night with that lunatic Scarlatti around.”
    â€œDid he lock you in there?” Callie asked.
    â€œNo,” Alicia said. “The door shut on me by mistake. I was—”
    â€œWhat’s that sound?” Frank cut in. They all held their breath, listening. A pounding came from the front porch, as if someone was climbing the stairs. Then a key rattled in the door, and the lock snapped open. “Scarlatti’s home!” Frank said. “Hide, or he’ll catch us.”
    The Hardys, Callie, and Alicia scrambled intothe secret closet and shut the door. It was dark, except for a faint thread of light under the door.
    â€œLet’s wait here for a moment to see what Scarlatti will do,” Joe said.
    â€œShhh,” Callie whispered. “He’ll hear us.”
    Nobody breathed as Scarlatti moved around in the downstairs hallway. After a minute he thumped upstairs, causing the staircase to shake around them. Soon the distant sound of a TV or radio filled the silent house.
    â€œLet’s hope he’s upstairs for the night,” Joe whispered. “Should we try to sneak out through the living room window?” He felt around the panel for a button or spring. “Strange,” he said. “I can’t find a way to open this door.”
    â€œI couldn’t, either,” Alicia said. “That’s why I banged when I heard Callie scream. I hoped you’d hear me and let me out.”
    â€œWell, your wish came true—for a moment, that is,” Joe muttered.
    â€œSo we’re stuck here till someone frees us?” Callie said anxiously.
    â€œRemember the secret passageway I mentioned when we came here to look for Roberto this morning?” Alicia said. “I wonder if it leads from this closet. After all, the door was secret, and we had to find a hidden button.”
    â€œThere’s no passageway that I can find,” Joe said, his voice muffled as he searched the back of the closet. “All I can feel is a wall.”
    â€œWhat are you doing here anyway, Alicia?” Frank asked. “Why were you inside the closet?”
    â€œI was just about to tell you when Roberto came in,” Alicia said, her voice a hoarse whisper. “I’m really scared, you guys, and at this point I don’t know where to turn.”
    â€œDo you know where your father is?” Frank asked.
    â€œNo. But when I got home this afternoon, I found a note in our mailbox. The note was from the kidnapper.”
    â€œWhat did it say?” Joe asked. He’d given up searching for the passageway and was standing between Callie and Frank.
    â€œIt said that if I want my father back, I have to pick up a manuscript from his safe-deposit box on Monday morning and leave it in a trash can on the wharf when the ten o’clock ferry docks. But if I talk to the police or to you guys about this, Dad will die.”
    Callie caught her breath. “So your father’s still alive! We have one more day to find him until you have to deliver the manuscript.”
    â€œDo you know anything about the manuscript?” Frank asked. “Why would anyone want it?”
    â€œI’m not sure,” Alicia whispered. “I only know Dad’s working on a book about shipwrecks.”
    â€œI wonder if that’s what the thief was looking for in the museum?” Frank said. “He could havestolen a few shipwreck artifacts to make the job look like a burglary.”
    â€œTrue,” Joe said. “He could have pulled down the papers on the shelves looking for the hard copy of the manuscript, then turned on the computer to see if he could find it there.”
    â€œDo you have a key to the safe-deposit box?” Frank asked Alicia.
    â€œThe kidnapper