"It cannot be true!" she said. "Tweedie has been here many, many years, and I have never had any reason to doubt his honesty."

Nevertheless, she felt that she should question the man. Unsuspecting of what he was about to hear, Tweedie smiled pleasantly when he appeared and asked Lady Douglas what she wished.

"I am at a loss for words," said Nancy's great-grandmother, "but I feel I must find out something from you. A report has come to us that you have the topaz-and-diamond brooch meant for Miss Nancy."

Tweedie went ash white and began to tremble. For several seconds he was speechless. Nancy felt sorry for the man and longed to help him, but she knew that this was Lady Douglas' affair.

By now Tweedie had recovered his wits. "Lady Douglas," he said with dignity, "I did not take the brooch. I know nothing about the pin. It is my belief that whoever accused me is covering up something himself."

Lady Douglas smiled at her long-time servant. "I was sure this would be your reply. I never doubted you."

Nancy now told Tweedie of having caught an American who, she believed, was in league with the sheep stealers. "I have a hunch that when the police obtain a confession from him and his friends, we will also get a clue to the missing heirloom."

To show she had complete confidence in him, Nancy asked Tweedie if he would help her make a mirror out of a goblet. The man looked surprised, but when told that it might aid in producing a clue in the mystery, he was eager to help. In a short time the quicksilver had dried and the cylindrical mirror was ready to be put to use.

Lady Douglas, Tweedie, and the other girls were interested onlookers as Nancy placed the goblet mirror upside down in the center of the canvas board containing the conglomerate of paint. This time, Nancy could distinguish a tower of stones.

"Have you any idea what this could be?" she asked her great-grandmother.

After a little study, both Lady Douglas and Tweedie thought that the tower might be part of ancient stone ruins not far away.

"It is in a deserted area," said Tweedie. "Would you like me to guide you girls there?"

"Oh, yes!" Nancy replied. "Since we found this picture where we know one of the sheep thieves was staying, I'm sure it has something to do with their work-it might even indicate another hideout!"

Plans were made for a trip early the following day. The girls learned that the ruins were called beehives because of their shape. They were also known as brochs, and dated back to prehistoric times.

Soon after breakfast the next morning the searchers set out. Tweedie directed Nancy onto a narrow, little-used country road and twenty minutes later the visitors got their first glimpse of the stone tower.

"It really is shaped like a beehive," Bess remarked, "except it has no top."

Nancy parked, and Tweedie led the girls across a meadow to view the ruins. The odd structure had no windows. It was made of varied sizes of fieldstones and stood about thirty feet high.

Tweedie said, "It must have been much higher at one time, and perfectly round. Only the front section is standing now."

He led the way to a very narrow opening-the only one into the broch. The pa.s.sage was barely two feet wide, and tunneled through the ten-foot-thick wall.

"This is an amazing sight," Nancy remarked, looking at the circular, upcurving stonework.

At intervals there were oblong openings with stone slabs laid crosswise in them like floors.

"What were those little rooms used for?" Bess asked.

Tweedie replied that historians were not sure. Some thought that during times of enemy invasions, an entire village of people would crowd into the broch, seal off the entranceway, and live there until the danger was over.

"Probably a whole family lived in one of those rooms," Tweedie continued. "Originally there was a circular staircase with a gallery at each level which permitted the inhabitants to go up and down. Also, they had a large hearth in the center for cooking. Now, I'll show you something else."

He led the girls around a low wall that was still standing and pointed out an entrance to a lower level. "That was where they had a well and got their water."

George asked, "If the beehive was solid-how did those people get any air?"

Tweedie said that most scholars felt the top was open and ventilation was provided through a latticed roof with a veranda. "Some archaeologists even believe this was used as a living room."

"Very cozy," Bess commented. "But I'd still prefer hotel accommodations!"

The others laughed. Then Nancy's thoughts turned to the mystery they were trying to solve. The girls looked around for clues but found none.

"There's certainly no sign of anyone's hiding out here," Nancy said finally.

Fiona turned to Tweedie. "Isn't there another broch up the road a ways?"

When he said Yes, Nancy urged that they go to see it. They reached this beehive a few minutes later and began investigating. Suddenly the young sleuth said excitedly, "Here are some bits of wool! And a piece of sheepskin!"

"You think the sheep thieves use this place?" Fiona asked.

"Yes," said Nancy. "And this evidence indicates they are not taking away live sheep to butcher or sell. They want only the wool and skins."

Bess groaned in distaste. "Ugh!" she said. "You mean the area around this broch might be a sheep graveyard?"

Nancy did not reply. She noticed that Tweedie had slipped away. She felt sure he was doing some investigating on his own, which proved to be true. He came back a few minutes later and announced that he had done a little digging with a sharp stone.

"I'm afraid this is indeed a sheep graveyard."

The group was able to piece the whole operation together now. Apparently the thieves lured a flock into some hidden glen, put them to sleep, and transported them by truck to this broch. Here they killed the sheep, sheared and skinned them, took the meat, then buried the rest to avoid detection by the police.

"I think we should return to Douglas House at once," said Nancy, "and inform the police office of our latest findings."

They sped back to the house and Nancy put in the call. After hearing the story, the officer promised to post men at the broch and try to catch the thieves red-handed.

"I will let you know as soon as we have any news," he promised.

The next day the girls attended church services and awaited word from the police. It was not until the following morning that the superintendent telephoned to say that nothing suspicious had happened at the broch.

"But down at Dumbarton on the Clyde," he added, "inspectors have come upon an illegal shipment of wool and sheepskins aboard a freighter destined for the United States."

After the call was ended, Nancy said to the other girls, "Dumbarton is directly south of where the houseboat stood on Loch Lomond. I'll bet that's the place Paul Petrie was heading for when we were chasing him."

George spoke up. "But Dewar and the other thieves weren't caught there. Where are they?"

Nancy shrugged. "They're not at the croft, not at the houseboat, and not at the broch. They're holed up somewhere, and it's my idea that they're waiting for a signal."

"From whom?" Fiona asked.

"Paul Petrie!"

The others were startled but could see the logic of Nancy's deduction. Bess and George recalled the bagpipe music in Mr. Dewar's room. "It could have been Petrie practicing," George said. "Then there was the piper on Ben Nevis who played the very same tune."

"I've just had a brainstorm," Nancy declared. "Great-Grandmother, it's a daring one, but I hope you won't have any objections. I'd like to dress in the Cameron kilt and the rest of the costume I wore before, climb Ben Nevis to the point where I saw that piper, and play Scots, WhaHae."