"We also learned," Dave added, "that this Zapp Crosson had his pilot's license."

Nancy was intrigued by this information. "So he could have flown the mysterious copter and known how to program the craft to fly itself."

The boys nodded and Burt said, "Nancy, we thought you'd probably know what to do next."

"Any clues about where the copter went?" she asked.

Dave said no one in the vicinity of Emerson knew anything about a helicopter which had the same registration number as the pilotless craft. The local police had made inquiries at a small airfield on the outskirts of Emerson, and also talked with members of a balloon club nearby. No one had a lead.

"It's still early enough to do some exploring before dinner," Dave said. "While you girls are in Emerson you can stay here in our first-floor guest room."

Bess giggled. "I didn't know you had one."

Dave grinned. "Oh, old Omega Chi Epsilon aims to keep up to date," he said.

The girls were led to a charming room with three beds in it and an adjoining bath.

"I'll take your car, Nancy, and fill it with gas," Burt offered. "Meet you all in front in ten minutes."

While the girls were washing their hands and combing their hair, George asked Nancy, "What are your thoughts about Zapp Crosson?"

Nancy replied, "I've been wondering if there was any connection between Zapp's project and an experiment on which Ned might have been working. Ned may have been keeping his own a secret until he had completed the experiment."

Just then the boys returned. They knew where the nearby airfields were located, so the five young people climbed into the car. Bess and George told them the story of the glowing eye.

Nancy felt lonesome without Ned, and started worrying even more about him than she had before. Sensing this, Dave said lightly, "Speaking of glowing eyes, I learned in bio cla.s.s today that a crayfish's eye has four thousand parts. Each one is a separate eye."

George grinned. "I didn't know the bottom of the sea had enough to see to require that many eyes."

"Oh, George," said her cousin Bess, "that's a horrible pun."

The others laughed. Burt, who was at the wheel, asked, "Where to?"

Nancy smiled. "Directly northeast from my home in River Heights."

"Emerson is slightly northeast," Burt replied, "so suppose we go due east."

Everyone agreed. Within ten minutes they came to a private flying field. A helicopter was just coming in. Burt turned into the driveway and went directly toward the whirlybird's landing spot.

A pleasant-looking young pilot leaped down. "Hi!" he said. "Want a ride?"

Nancy jumped from the car. "Do you take people sightseeing?" she asked as an idea flashed into her mind.

"Sure thing. Any place within a radius of a hundred and fifty miles. My rates are low."

Nancy thought so too when she heard what they were.

"How many pa.s.sengers can you take?"

"Three."

"We'll go," Nancy said. "Are you ready?"

"In a few minutes. I'll fill 'er up with fuel, and take you up for an hour."

While the pilot was doing this, Nancy quickly explained to her friends that she thought it was a marvelous opportunity to view the countryside near Emerson. "Which two of you want to go?"

Bess and Dave offered to stay on the ground. "I'd like to look around and see the planes here," Dave said.

Quarter of an hour later the three pa.s.sengers climbed aboard and the helicopter rose.

"I'm Glenn Munson," the pilot said. "Anything in particular you'd like to see?"

Nancy introduced herself and her friends. "Yes. As many airfields public and private that you have time to show us."

Glenn raised his eyebrows. "For any special reason?"

Nancy told of the mysterious helicopter landing on the Drews' lawn. "Have you ever seen or heard of a robot copter around this area?" she asked.

"Sure. A friend of mine who's a computer expert has one. Want to meet him?"

Nancy was so excited she could hardly keep her voice calm. But she managed to say, "We'd love to."

Munson steered his craft in a half circle, flew a few miles, then descended. "There's Jerry now," he said, "just tuning up his robot copter to take off." Jerry's helicopter was much smaller than the one which had landed on the Drews' front lawn, and Nancy a.s.sumed this was the reason the police had not mentioned it.

She and the others jumped down from their craft and were introduced to Jerry Faber, a tall, lanky young man with twinkling eyes.

"Nancy's looking for a certain robot copter," Glenn said.

"One that's larger than yours," she told Faber.

Jerry grinned. "Sorry I can't help you. But come, I'll show you my real beauty of a copter."

He led the group to a barn at one edge of the field and opened the door. Before them stood a big, shiny new helicopter.

"There's Emmy," Jerry said proudly. "She's not a robot but I can take ten pa.s.sengers in her. And she has a long range-three hundred and fifty miles."

Nancy was disappointed that neither helicopter was the one she had hoped to find, but said, "This big one certainly is beautiful. Do you use it just for pleasure?"

"No, I fly executives of nearby companies on short business trips, and sometimes other people. I had a mysterious pa.s.senger a week ago. He didn't even give me his full name. He just said, 'Call me Crossy.' "

"Crossy?" Burt burst out. "What did he look like?"

"Had bright red hair."

"He's the one!" Burt exclaimed. "We think-" A warning look from Nancy kept him from saying, "We think he's a kidnapper."

"Do you know him?" Glenn asked in surprise.