The Hidden Staircase by Carolyn Keene

the details.
    “What’s going to happen to you next?” the housekeeper exclaimed.
    The young sleuth laughed. “Something good. I hope.”
    She asked Hannah to look for her copy of the River Heights Gazette of the Tuesday before. In a few minutes the housekeeper brought it to the phone and Nancy asked her to turn to page fourteen. “That has the classified ads,” she said. “Now tell me what the ad is right in the center of the page.”
    “Do you mean the one about used cars?”
    “That must be it,” Nancy replied. “That’s not in my paper.”
    Hannah Gruen said it was an ad for Aken’s, a used-car dealer. “He’s at 24 Main Street in Hancock.”
    “And now turn the page and tell me what ad is on the back of it,” Nancy requested.
    “It’s a story about a school picnic,” Hannah told her. “Does either one of them help you?”
    “Yes, Hannah, I believe you’ve given me just the information I wanted. This may prove to be valuable. Thanks a lot.”
    After Nancy had finished the call, she started to dial police headquarters, then changed her mind. The ghost might be hiding somewhere in the house to listen—or if he had installed microphones at various points, any conversations could be picked up and recorded on a machine a distance away.
    “It would be wiser for me to discuss the whole matter in person with the police, I’m sure,” Nancy decided.
    Divulging her destination only to Helen, she told the others she was going to drive downtown but would not be gone long.
    “You’re sure you feel able?” Aunt Rosemary asked her.
    “I’m perfectly fine,” Nancy insisted.
    She set off in the convertible, hopeful that through the clue of the used-car dealer, the police might be able to pick up the name of one of the suspects.
    “They can track him down and through the man locate my father!”

CHAPTER XIV
    An Urgent Message
    “EXCELLENT!” Captain Rossland said after Nancy had told her story. He smiled. “The way you’re building up clues, if you were on my force, I’d recommend a citation for you!”
    The young sleuth smiled and thanked him. “I must find my father,” she said earnestly,
    “I’ll call Captain McGinnis of the River Heights force at once,” the officer told her. “Why don’t you sit down here and wait? It shouldn’t take long for them to get information from Aken’s used-car lot.”
    Nancy agreed and took a chair in a corner of the captain’s office. Presently he called to her.
    “I have your answer, Miss Drew.”
    She jumped up and went over to his desk. The officer told her that Captain McGinnis in River Heights had been most co-operative. He had sent two men at once to Aken’s used-car lot. They had just returned with a report.
    “Day before yesterday an athletic-looking man with a crinkly ear came there and purchased a car. He showed a driver’s license stating that he was Samuel Greenman from Huntsville.”
    Nancy was excited over the information. “Then it will be easy to pick him up, won’t it?” she asked.
    “I’m afraid not,” Captain Rossland replied. “McGinnis learned from the Huntsville police that although Greenman is supposed to live at the address he gave, he is reported to have been out of town for some time.”
    “Then no one knows where he is?”
    “Not any of his neighbors.”
    The officer also reported that Samuel Greenman was a person of questionable character. He was wanted on a couple of robbery charges, and police in several states had been alerted to be on the lookout for him.
    “Well, if the man I saw at my car is Samuel Greenman, then maybe he’s hiding in this area.”
    Captain Rossland smiled. “Are you going to suggest next that he is the ghost at Twin Elms?”
    “Who knows?” Nancy countered.
    “In any case,” Captain Rossland said, “your idea that he may be hiding out around here is a good one.”
    Nancy was about to ask the officer another question when his phone rang. A moment later he said, “It’s for you, Miss