George held up her two hands in a thank-you gesture. Accompanied by Bess, Nancy and Julie Anne, she went to her cabin for dry clothes.

The boys stayed to see the rest of the operation. Soon the two barges were lashed together. The journey back to Cairo began.

About noontime they entered a lock beside the Kentucky sh.o.r.e. Intrigued, the young people stood at the rail watching the towboat slowly and skillfully push the triple line of barges between the concrete walls.

"The captain has to be good," said Ned. "He doesn't have much clearance on either side."

"That's for sure," said a man, standing on the wall. He wore a yellow hardhat.

"You're an Army Engineer, aren't you?" Art asked him. "I know your Corps is in charge of dams and locks."

"That's right," the man replied.

As they all chatted with the engineer, the Sally O and her tow slowly sank lower between the walls.

Finally, far ahead, the great gates swung open and the Sally 0 rode out into the river. As the towboat pa.s.sed through the opening, several other engineers waved from the lock wall.

Immediately afterward Nancy sought out Captain Boge. She asked if he could radio the Illinois State Police to find out if they had any word on Bob Snell or if Kadle or any of his gang had been caught at the old house.

"I guess we'd all like to know," Boge said.

He turned to his radio and made the call. To Nancy's disappointment, she heard the answering officer give negative replies to both queries.

Nancy went back to the deck and relayed the depressing news to the others. "Hypers!" George exclaimed. "Where is Bob Snell?"

A few minutes later luncheon was served. There had been no regular seating arrangements. The young people had moved around freely but Bess had noticed that whenever possible Art had placed himself next to Nancy. Later she mentioned this to Nancy, who laughed it off.

"Don't laugh," Bess said. "It's serious. I was hoping Art was going to stick close to Julie Anne but that didn't last long. I'm going to do something about this!"

Nancy begged her not to. Bess said no more, but Nancy noticed that all afternoon she made a point of searching out Art and talking with him.

"Dave isn't going to like this one bit," Nancy thought. "Oh dear! Why can't things run along smoothly?"

Ned and Art stayed far apart. Nancy kept moving around to talk to everyone but little by little a strained air came over the whole group.

Apparently Captain Boge noticed this. At suppertime he said, "I want an honest answer to a question. Have you young folks been bored with this trip?"

"Oh no!" Nancy replied. "It's been full of excitement. How could we possibly be bored?"

The captain looked down at the table pensively. "You have all become so quiet I thought maybe something was wrong."

They all a.s.sured him he had nothing to worry about. The trip had been perfect. Apparently the captain decided to change the subject.

"Did you know a ghost can sometimes be seen at night walking on this river?"

George looked at him skeptically. "You're spoofing."

"You can decide for yourself," he said.

He told them that many years ago a young man and his sweetheart were coming down the river in a small sailboat. In a sudden freak wind the mainsail shifted so quickly it knocked the girl overboard.

"According to the story, she was never seen alive again, but her spirit appears on the water, hoping her lover will come back to her. If you watch the Illinois sh.o.r.e real closely, you might see her ghost tonight. Lots of folks say they have. I've never seen her, but tonight might be just the right time."

The young people did not believe a word of the legend, but they trooped to the deck in a more lighthearted mood than they had been in before. Nancy, Bess, and Captain Boge were pleased.

The whole group stayed up until midnight watching for the apparition, but did not see it. The next morning, however, Julie Anne declared she had been the girl ghost in her dreams.

"The young man in the boat who came to get me-was Art!" Everyone laughed and the other girls wondered if there were a double meaning in Julie Anne's remark.

The young people spent another pleasant day on the boat. At nightfall they saw the familiar sh.o.r.eline of Cairo ahead.

They had already packed their bags and began saying good-by to the captain and crew. As the tugboat drew alongside to take them off the Sally 0, the men gathered to wave.

Nancy lingered a moment to speak privately to Captain Boge. "Please don't worry about us. We honestly had a marvelous time and I a.s.sure you we're all good friends." The captain squeezed her hand understandingly and wished her well.

As soon as they reached the dock, Nancy asked Ned if he would mind telephoning Roscoe Thompson, the helicopter pilot. "Ask him to meet us at Cairo. We can taxi to the airfield."

The others waited for him. He rejoined them, smiling. "Roscoe will be there."

By the time the group reached the field, he was waiting for them. Nancy introduced him to Bess, George, Ned, Burt, and Dave.

"It'll be a tight squeeze," he said, "but we'll manage. It's not a long ride to the dig."

Before leaving, Nancy telephoned the State Police and learned there was no news of Bob Snell, and Kadle and his pals were still at large.

"I suppose they'll come to the dig," she thought. "We must keep our eyes open."

When the helicopter was airborne, Nancy asked Roscoe if he had done any searching from the air for Bob Snell.

"Yes, but I didn't spot anything suspicious. I sure hope somebody finds him soon."

As the helicopter set down, all the diggers heard it and ran out to greet Nancy and her friends. During the introductions and chatter that followed, Roscoe took off. Nancy immediately mentioned Bob Snell.

"His father came out here the day you left to meet your friends," Theresa said. "Mr. Snell is staying in Cairo and making his own investigation."

The newcomers were besieged with questions about the towboat trip and the treasure hunt.

Julie Anne and Art joined in giving answers. Everyone was glad to hear A.C.E. Armstrong had been rescued and thought it was clever of Nancy to have tracked him down.

"He was able to clear up a good bit of the mystery," she said. "We can start all over again looking for the message in the hollow oak."

The group went to the girls' farmhouse to hear the whole story over an evening snack. Afterward, Nancy saw Bess and Theresa walking up and down in front of the house together. The girl was talking animatedly and the director was nodding and smiling. Nancy wondered what the conversation was about, but Bess offered no explanation and Nancy did not prod her.

When it was time for the boys to leave, Nancy noticed that Art did not invite her friends to go with him. He stalked ahead alone. Todd took charge of them and they disappeared along the path leading to the boys' dormitory.

There were two extra beds in one of the girls' rooms. Bess and George were a.s.signed to them.

Early the next morning when the boys arrived Art was on his motorcycle. Nancy explained to Theresa that she had asked him to go over to Clem Rucker's home and see if he would rent his farm truck to her. She planned on Ned's driving it in her search for the special oak tree.