The girl flushed angrily, but said nothing.

Theresa urged Nancy to look for more of the skeleton and she worked diligently the rest of the day, but had no luck.

Finally it was quitting time. The weary diggers came to the surface, and went to change their clothes. Some started to prepare supper.

Nancy came outside and dropped to the ground for a brief rest and to think about the secret in the hollow oak. She found herself dozing and turned on her side.

Suddenly her attention was directed to a sound she detected on the ground. Listening closely, Nancy decided it was a car. Who was coming?

She sat up and watched the road that led to the dig. No car appeared, so again the young detective put her ear to the ground and listened. Now there was nothing but silence.

"Someone must have parked," she thought. The idea made her uneasy. She stood up and went into the house. A few of the boys had gathered in the living room. Nancy told them what she had heard.

"Maybe I'm silly to be suspicious," she said, "but I have a hunch that Kit Kadle may come here and attempt some mischief. You know, two people have warned me against him."

Art spoke up. "I don't think you're silly at all. This house and the dig should be protected as well as you. Okay with you guys if we take turns standing guard here at night?"

"Great idea," replied Bob Snell. "You give out the shifts and I'll be on the job."

Nancy smiled at them all. "I'm sorry to be a troublemaker in your group, but-"

"Stop that!" Art interrupted her. "It will be an exciting change to play detective." He arranged time shifts and took the first one himself.

Dinner was announced. The group ate heartily and retired early. Nancy found it hard to sleep. She could not keep her mind off the fact that Kit Kadle might show up at the farmhouse. If so, what would he try to do? She felt sure he was the one who had let the goat into the house. This time his mischief might cause serious harm.

Finally, after tossing and turning for an hour, she got up, pulled on her clothes, and went outdoors. It was a bright, starry night and objects were clearly distinguishable.

Almost instantly Art was at her side. He gave a low chuckle. "I thought you were Kit Kadle'sgirl friend."

Nancy grinned and started to walk around the farmhouse with him. Just then they became aware of light footsteps not far away. The couple hid behind bushes.

The stealthy footsteps came from the rear of the house. Nancy and Art fully expected someone to enter the front door. Instead they saw a man going toward the dig carrying a ladder.

Moving quietly the couple followed him across the yard and into the field. They saw the figure set the ladder into the excavation.

Nancy whispered. "It's time to act!"

She and Art loped with light steps toward the dig. The man heard them and turned quickly. Nancy recognized him. Art beamed his flashlight on the figure.

"Tom Wilson!" Nancy whispered.

They ran toward the man to question him about why he had come there. But before they could reach him, Wilson took off like a frightened deer.

"He's not limping!" Nancy observed as she and Art pursued the fleeing figure. "We mustn't lose him!" she exclaimed.

Wilson was fleet-footed. He had gone straight up the road, but to the young people's amazement had outdistanced them. When they lost sight of him, Nancy stopped and put her ear to the ground.

"He's still on the road," she reported, catching up to Art.

A few seconds later Nancy listened again. They were closer now! She and Art put on extra speed.

"We're catching up!" she gasped.

They raced along the road like marathon runners.

CHAPTER VII.

River Pirates

WHILE Nancy and Art were running after the fleeting figure, Todd Smith came to the farmhouse to relieve Art. He looked all around for his friend and finally decided he had better report his absence to Theresa Bancroft.

As he reached the door, Julie Anne rushed out. She almost b.u.mped into him.

"Nancy's not in her bed!" she exclaimed.

Todd looked puzzled. "I was just coming to report that Art's missing. I'm sure he wouldn't have left the farmhouse unguarded. Something strange must have happened, Julie Anne!"

"They're probably together," she said. "I hope they're not in danger! Let's look for them."

Both Julie Anne and Todd had flashlights. They began walking around the grounds and finally came to the dig.

"Look!" Julie Anne exclaimed. "Someone put a ladder into the pit."

The two flashlights did not reveal anyone in the excavation. The searchers were more puzzled than ever.

"What could have happened?" Julie Anne asked.

"Listen! I hear people talking," Todd said. They moved toward the sound and in a few minutes saw two flashlights bobbing. Their own lights revealed Nancy and Art.

"What's going on?" Todd demanded.

"Did you see the ladder?" Art queried.

"Yes. Whose is it?"

Nancy and Art related what they had seen and their chase after Tom Wilson. "We had almost caught up to him when he jumped into a car and rode off," Nancy explained.

"But I thought Tom Wilson was lame," Julie Anne remarked.

"So did I," Nancy replied. "That man's a fake and I'm sure now he's Kit Kadle in disguise."

Todd wondered what the intruder had planned to take out of the dig. No one could hazard a guess, since all the artifacts and fossils uncovered so far had been brought to the laboratory.

"Have you any idea, Nancy?" Todd asked. She shook her head.

By this time Art had pulled the ladder from the excavation. It was crudely made of narrow tree branches from an oak.