The Secret of the Caves by Franklin W. Dixon

there,” Chet burst in.
    Dumfounded, the three girls listened raptly to the story of the boys’ adventures.
    â€œYou mean you want us to help you on a detective case?” Iola said happily. “Oh, we’d love to!”
    A determined look crossed Mary’s pretty face. “If Callie and Iola are going to help you boys find my brother, I want to help, too.”
    â€œBut—but—” Chet started to protest.
    â€œNo buts about it,” Mary said emphatically. “All three of us girls will be detectives!”
    Mary’s enthusiasm amused Joe and Chet. But Callie and Iola were delighted to have her join them in applying for waitress jobs at the Palais Paris.
    â€œWe’ll call ourselves the three musketeers!” Iola said proudly.
    â€œUgh!” said Chet. “I can just see you now dueling with steak knives.”
    Iola gave her brother a withering look, then turned to Joe with a bright smile. “What do you want us to do when we get there? Shall we go under assumed names?”
    â€œTo answer your second question first,” said Joe. “You and Callie give your names, but I don’t think Mary should use her last one—just in case these people have read about her brother’s disappearance.”
    â€œAll right,” Mary said promptly. “I’ll call myself Mary Temple.”
    â€œGood,” Joe replied. “In answer to your first question, lola—if and when you get to be waitresses, just keep your ears and eyes open for anything suspicious going on at the Palais Paris.”
    â€œAnd not too much giggling, either,” Chet said with a brotherly wave of his hand.
    â€œOf course not, silly!” Iola retorted. “When do we start?”
    â€œFirst thing tomorrow,” Joe said. “We’ll meet here at eight o‘clock.”
    â€œMeantime”—Iola’s eyes twinkled—“we gals can practice balancing trays.”
    Afterward, Joe rode to Bayport with Callie in her sports car. “I’ll pick you up in the morning,” she said, pulling up at the Hardy home. “Bye now.”
    Joe was disappointed to learn that his father was out of town. “Your dad won’t be back until sometime tomorrow,” said Mrs. Hardy. “By the way, did you boys find a spinning wheel?”
    â€œWell—er—yes,” Joe replied. “But it needs a little work. We’ll fix it up, though, Mom.” He added apprehensively, “Aunt Gertrude hasn’t arrived yet?”
    â€œNo, but I expect her any day.”
    Joe quickly briefed his mother on their recent adventures, including the cap clue and the plan to return to Rockaway. “There’s a phone at the general store in case you want to reach us,” he said. Joe had supper and retired early. Right after breakfast he took enough money from the brothers’ safe to cover the balance on the spinning wheel and retrieve Frank’s watch.
    Promptly at eight o‘clock Joe and Callie arrived at the Morton farm, and the five young people set off in Chet’s jalopy. Iola sat next to Joe as the teen-agers drove happily along the highway to Rockaway.
    Frank and Biff met them at the campsite, somewhat surprised to see Mary Todd.
    â€œI have news for you,” Frank said. “Old Man Tuttle doesn’t sell those foreign caps.”
    â€œI told you Wilson was nutty,” Joe commented.
    It was then decided that Biff should drive the three girls to the restaurant. Frank explained, “The Palais Paris people already know Joe and me. They might get suspicious if we show up with you.”
    â€œWell, I don’t see why we girls can’t drive alone,” said Iola. “We have our licenses with us.”
    Although the Hardys knew that Callie and Iola were good drivers, they insisted that Biff go along as a precautionary measure.
    â€œThere may be a bunch of gangsters hiding out there,” Chet quipped. “And