He drew a coin from his pocket the size of a half dollar and handed it to Nancy. The wording on the coin was so worn that she could not make it out and reached into a pocket of her jeans for a magnifying gla.s.s. Nancy held it over the coin.

A moment later she asked excitedly, "Clem, do you know what it says on here?"

CHAPTER V.

Air Spy

JULIE Anne and Clem listened in fascination while Nancy translated what was engraved on the coin. It was in French. At the top were the initials P. F. and underneath a short prayer.

"Pere Franois!" exclaimed Julie Anne.

"I'm sure it is," said Nancy. "He must have dropped it in this area or else the Indians took it away from him and lost it themselves."

There was no date on the metal disk but the girls a.s.sumed it was over three hundred years old.

"This isn't exactly a good-luck piece," Nancy stated. "It's much more."

Clem looked at her intently. "Whatever it is, it don't mean nothin' to me. I bought it from the lad who found it. I'm givin' it to you, Nancy."

"May I pay you something for it?" she asked.

Clem Rucker laughed. "What would I do with a lot o' money? I only gave that lad twenty-five cents, so I'm not out much."

"Well, this is a fabulous gift," Nancy said, "and I shall treasure it."

"Anyway," said Clem, standing up, "I hope it brings you good luck in solvin' the mystery o' the hollow oak. We'd better go on."

He followed a course due east and in about half an hour they came to another hollow oak. This one was still standing and from its size they judged it was centuries old. Clem said he thought the tree might have been there as long as four hundred years.

Nancy walked around the oak and found a rotted-out section. She beamed her flashlight inside and put her face to the edge of the hole to see what was in the cavity. Unfortunately she found nothing.

No marker was showing but there was definitely a hump at one place in the bark. Clem produced a chisel from his car. He and Nancy took turns chipping and peeling off bark until they uncovered part of a lead plate.

A short time later the three searchers became aware of a helicopter circling overhead. As they glanced up, Nancy detected someone with binoculars looking at them.

"He's spying on us!"

The copter suddenly flew off and disappeared. But not before Nancy had opened her purse and written down the license number on a pad. She suspected that Kit Kadle might be a pa.s.senger in the helicopter and she meant to find out.

"Have you ever seen that copter before?" Nancy asked Clem.

"Oh yes," the farmer replied. "Guess he's one o' them free-lance pilots. Takes folks up to give 'em a bird's-eye view of the burial mounds and the river."

Meanwhile Julie Anne, who had taken the chisel from Clem, had chipped off more of the bark. Suddenly she exclaimed, "Here's another Pere Franois plate! There's no date on this one and only the initials P. F., but I can see a faint arrow. This one points directly south."

"It may lead to what was once an Indian settlement," Nancy mused. "We know Pere Franois traveled from village to village trying to convert the Indians."

"Could be," said the farmer, "but I don't reckon we can find out today. I'm sorry, ladies, but I have to get home now and tend to my ch.o.r.es."

"When can you help us again?" Nancy asked him.

Clem said he would not be able to for another three days and he did not know of anyone else who might take Nancy around on her search.

"Anyway," said Julie Anne, "I won't be able to leave the dig."

"He's spying on us!" Nancy exclaimed

Nancy was disappointed over the delay. But in the meantime she would try to find out about the helicopter pilot and who his pa.s.senger was.

Clem took a shortcut back to the dig. The girls thanked him for the trip and said they would expect him in three days.

As Clem drove away, Nancy thought, "I'll have to figure a way to get to town so I can find out about that copter."

It was nearly suppertime and the diggers had stopped work. Nancy and Julie Anne found the other girls preparing a wholesome meal. Meanwhile, the bovs were cleaning the artifacts and fossils which they had discovered at the bottom of a new pit.

All of them were eager to hear what progress Nancy had made on her case. She related the details, including Clem's story about the catfish. The others laughed and Art burst into a song from the opera Porgy and Bess about Catfish Row.

When he finished, Nancy announced, "I'd like to drive some place to make a phone call. I forgot to ask Clem if he has a telephone."

Art spoke up. "I have a two-seater motorcycle here," he told her. "I'll be glad to take you to town."

"That's wonderful," Nancy said. "Could we go tomorrow morning?"

"You bet," he said. "But it will have to be early. My shift begins at ten A.M."

"Where do you think the pilot came from?" Nancy asked him.

Art said there was a small airfield outside the town of Walmsley, the nearest one to the dig.

They had a very early breakfast and left the dig site at seven o'clock. Art drove directly to Walmsley and went on to the airfield which was about three miles out of town.

When they arrived Nancy stepped into the office and asked who owned the helicopter with the license number she had copied on her pad. She showed it to the man in charge.

"Oh, that's Roscoe Thompson," he replied. "Is he around now? I'd like to speak to him," Nancy said.

Thompson was at the end of the field checking his helicopter. Nancy and Art walked over to him.

Roscoe proved to be a very pleasant young man and gladly answered Nancy's questions. His pa.s.senger the day before had been a man named Tom Wilson.

"Where does he come from?" Nancy questioned.

"I really don't know. He didn't talk much. Said he wanted to make the trip over the site of the various Indian burial mounds. Mr. Wilson was interested to learn their locations because he's an amateur archaeologist.

"By the way," Roscoe went on, "Mr. Wilson was very curious about two girls and a man who were hacking at an oak tree. Was one of them you?"

"Yes," Nancy admitted. "Why did your pa.s.senger want to know what I was doing?"