The young sleuth picked a different spot, but the results were the same. There was no open space behind that portion of the attic wall.
"My hunch wasn't so good," said Nancy.
Helen suggested that they give up and go downstairs. "Anyway, I think the postman will be here soon." She smiled. "I'm expecting a letter from Jim. Mother said she would forward all my mail."
Nancy did not want to give up the search yet. But she nodded in agreement and waved her friend toward the stairs. Then the young detective sat down on the floor and cupped her chin in her hands. As she stared ahead, Nancy noticed that Helen, in her eagerness to meet the postman, had not bothered to go quietly down the attic steps. It sounded as if Helen had picked the squeakiest spot on each step!
Nancy heard Helen go out the front door and suddenly realized that she was in the big mansion all alone. "That may bring the ghost on a visit," she thought. "If he is around, he may think I went outside with Helen! And I may learn where the secret opening is!"
Nancy sat perfectly still, listening intently. Suddenly she flung her head up. Was it her imagination, or did she hear the creak of steps? She was not mistaken. Nancy strained her ears, trying to determine from where the sounds were coming.
"I'm sure they're not from the attic stairs or the main staircase. And not the back stairway. Even if the ghost was in the kitchen and unlocked the door to the second floor, he'd know that the one at the top of the stairs was locked from the other side."
Nancy's heart suddenly gave a leap. She was positive that the creaking sounds were coming from somewhere behind the attic wall!
"A secret staircase!" she thought excitedly. "Maybe the ghost is entering the second floor!"
Nancy waited until the sounds stopped, then she got to her feet, tiptoed noiselessly down the attic steps and looked around. She could hear nothing. Was the ghost standing quietly in one of the bedrooms? Probably Miss Flora's?
Treading so lightly that she did not make a sound, Nancy peered into each room as she reached it. But no one was in any of them.
"Maybe he's on the first floor!" Nancy thought.
She descended the main stairway, hugging the wall so she would not make a sound. Reaching the first floor, Nancy peered into the parlor. No one was there. She looked in the library, the dining room, and the kitchen. She saw no one.
"Well, the ghost didn't come into the house after all," Nancy concluded. "He may have intended to, but changed his mind."
She felt more certain than at any time, however, that there was a secret entrance to Twin Elms Mansion from a hidden stairway. But how to find it? Suddenly the young sleuth snapped her fingers. "I know what I'll do! I'll set a trap for that ghost!"
She reflected that he had taken jewelry, but those thefts had stopped. Apparently he was afraid to go to the second floor.
"I wonder if anything is missing from the first floor," she mused. "Maybe he has taken silverware or helped himself to some food."
Going to the back door, Nancy opened it and called to Helen, who was now seated in the garden with Miss Flora and Aunt Rosemary. "What say we start lunch?" she called, not wishing to distress Miss Flora by bringing up the subject of the mystery.
"Okay," said Helen. In a few moments she joined Nancy, who asked if her friend had received a letter.
Helen's eyes sparkled. "I sure did. Oh, Nancy, I can hardly wait for Jim to get home!"
Nancy smiled. "The way you describe him, I can hardly wait to see him myself." Then she told Helen the real reason she had called her into the kitchen. She described the footsteps on what she was sure was a hidden, creaking stairway, then added, "If we discover that food or something else is missing we'll know he's been here again."
Helen offered to inspect the flat silver. "I know approximately how many pieces should be in the buffet drawer," she said.
"And I'll look over the food supplies," Nancy suggested. "I have a pretty good idea what was in the refrigerator and on the pantry shelf."
It was not many minutes before each of the girls discovered articles missing. Helen said that nearly a dozen teaspoons were gone and Nancy figured that several cans of food, some eggs, and a quart of milk had been taken.
"It just seems impossible to catch that thief," Helen said with a sigh.
On a sudden hunch Nancy took down from the wall a memo pad and pencil which hung there. Putting a finger to her lips to indicate that Helen was not to comment, Nancy wrote on the sheet:
"I think the only way to catch the ghost is to trap him. I believe he has one or more microphones hidden some place and that he hears all our plans."
Nancy looked up at Helen, who nodded silently. Nancy continued to write, "I don't want to worry Miss Flora or Aunt Rosemary, so let's keep our plans a secret. I suggest that we go to bed tonight as usual and carry on a conversation about our plans for tomorrow. But actually we won't take off our clothes. Then about midnight let's tiptoe downstairs to watch. I'll wait in the kitchen. Do you want to stay in the living room?"
Again Helen nodded. Nancy, thinking that they had been quiet too long, and that if there was an eavesdropper nearby he might become suspicious, said aloud, "What would Miss Flora and Aunt Rosemary like for lunch, Helen?"
"Why, uh—" Helen found it hard to transfer to the new subject. "They—uh—both love soup."
"Then I'll make cream of chicken soup," said Nancy. "Hand me a can of chicken and rice, will you? And I'll get the milk."
As Helen was doing this, Nancy lighted a match, held her recently written note over the sink, and set fire to the paper.
Helen smiled. "Nancy thinks of everything," she said to herself.
The girls chatted gaily as they prepared the food and finally carried four trays out to the garden. They did not mention their midnight plan. The day in the garden was proving to be most beneficial to Miss Flora, and the girls were sure she would sleep well that night.
Nancy's plan was followed to the letter. Just as the grandfather clock in the hall was striking midnight, Nancy arrived in the kitchen and sat down to await developments. Helen was posted in a living-room chair near the hall doorway. Moonlight streamed into both rooms but the girls had taken seats in the shadows.
Helen was mentally rehearsing the further instructions which Nancy had written to her during the afternoon. The young sleuth had suggested that if Helen should see anyone, she was to run to the front door, open it, and yell "Police!" At the same time she was to try to watch where the intruder disappeared.
The minutes ticked by. There was not a sound in the house. Then suddenly Nancy heard the front door open with a bang and Helen's voice yell loudly and clearly:
"Police! Help! Police!"
CHAPTER XI
An Elusive Ghost
BY THE time Nancy reached the front hall, Tom Patrick, the police guard, had rushed into the house. "Here I am!" he called. "What's the matter?"
Helen led the way into the living room, and switched on the chandelier light.
"That sofa next to the fireplace!" she said in a trembling voice. "It moved! I saw it move!"
"You mean somebody moved it?" the detective asked.
"I—I don't know," Helen replied. "I couldn't see anybody."
Nancy walked over to the old-fashioned sofa, set in the niche alongside the fireplace. Certainly the piece was in place now. If the ghost had moved it, he had returned the sofa to its original position.
"Let's pull it out and see what we can find," Nancy suggested.