Chief McGinnis agreed with Mr. Drew and added his caution. Before Nancy could step down, the rotors suddenly stopped whirring and the engine became silent.

"Something went wrong!" George exclaimed.

"Thank goodness," said Bess. "Otherwise Nancy might be up in the air and off on a dangerous mission!"

Nancy nodded, but was more interested in the helicopter. "It must be remote-controlled," she commented, "and can take off and land at any time."

"But why did its engine stop?" Bess asked.

Nancy a.s.sumed that the operator had used a sensitized gadget which let him know whenever there was added weight in the helicopter, indicating that someone was aboard uninvited.

"We'll prevent it from flying away," said the chief. "Tomorrow the police will take it. Girls, would you find some heavy pieces for my men to pile inside? I want to keep the copter here if possible until we can check on its ownership and move it."

While the husky police chief and a few of his officers clung to the craft, Nancy and her father hurried into the garage and brought out a heavy tire rim, an iron bucket left by a painter, and part of an unused steel fence as ballast.

"That should help," the chief said.

George had a suggestion. "Why don't we tie the copter down? I saw a lot of strong, thick rope in the garage."

The others agreed and the craft was securely anch.o.r.ed to a tall, st.u.r.dy-looking tree. Bess and George said they must leave but would be back in the morning to help Nancy on the case. Chief McGinnis ordered one man to stay on duty. He and the rest drove off.

As Nancy and her father started for the front door, their housekeeper, Mrs. Hannah Gruen, arrived in a taxi. She alighted and stared in astonishment at the helicopter, then at the Drews. Mrs. Gruen, middle-aged, and adored by Nancy, had lived with the Drews since the death of Nancy's mother when the girl was only three years old.

Mr. Drew smiled. "We had a robot visitor," he told the housekeeper. "Nancy will tell you the whole story. I must run back to the office, but I'll be home by ten tonight. Please call Miss King and tell her I'm returning."

Nancy made no comment. The last thing in the world she wanted to do was talk to Marty King. She turned to Hannah. "Will you do it, please?"

Unaware of Nancy's reason for the request, the housekeeper made the call, then went to the kitchen to start dinner preparations.

Nancy followed. "Don't cook much for me. I'm not hungry."

"Why, what's the matter, dear?" Hannah asked.

"Lots of things. But worst of all, we think Ned has been kidnapped."

"What!"

Nancy explained and ended by saying, "I want to find Ned, but I don't know which direction to go."

"That's not like you," the housekeeper said kindly. "You've had a bad shock, dear. I suggest you eat a simple dinner and go right to bed. In the morning you'll be refreshed and ready to start on the case."

"But which case?" Nancy asked. "Ned, the robot copter, Cyclops, the glowing eye-"

"Stop!" Mrs. Gruen exclaimed. "That's three too many. Nancy, do be sensible. Why not concentrate on Ned? Call Burt or Dave and see if there's any news."

Nancy took Hannah's advice and went to the phone. Burt answered quickly, hoping the police were calling to report a clue to Ned's whereabouts. He told Nancy there was no news from or about Ned.

"Have Mr. and Mrs. Nickerson been notified?" Nancy asked.

"Yes, and they haven't heard anything. Apparently you're the only one who received a message."

During dinner Nancy and Hannah discussed the strange happenings of the day, but the young detective refrained from mentioning Marty King and her part in trying to solve the glowing eye mystery.

Later Nancy called the Nickersons, expressed her concern, and told them about the note signed by their son. "Do you know anything about Cyclops?"

"Cyclops? No," Mr. Nickerson replied, and his wife on an extension phone said, "We never heard Ned mention it, so I'm sure it must be some new contact. Oh, Nancy, use your best detective instincts and find him," Ned's mother pleaded.

"I'll do my best," Nancy promised.

By nine-thirty Nancy felt so exhausted she decided not to wait for her father's return, but to go to bed. She soon drifted off into a sound sleep. Several hours later she was awakened by a tremendous racket on the front lawn and jumped out of bed.

Nancy rushed to a window just in time to see the robot helicopter rising from the lawn!

CHAPTER III.

A Glowing Eye

By the time Nancy had put on robe and slippers and had run into the hall, her father and Hannah Gruen were already there. Without a word all three rushed down the front stairway and out the door. Mr. Drew switched on a light that flooded the lawn.

The guy ropes which had held the helicopter down now lay on the ground. The craft itself was out of sight, but the moving lights in the sky indicated the copter had taken a northeasterly direction.

"That's toward Emerson," Nancy said. Then her thoughts turned to the officer who had been left by the police to watch the helicopter. "Where's the guard?"

He was not in sight and Hannah suggested, "Maybe he was kidnapped too!"

"And possibly taken away in the copter," Mr. Drew added.

Nancy had a different idea. "He may have been knocked out and left behind. Let's look around."

They did not have to search far. The guard was lying unconscious in the Drews' garage. The officer did not respond to their first-aid treatment, so Nancy's father phoned headquarters to report the incident and request medical help.

An ambulance with a police surgeon and a patrol car with two other officers reached the house within minutes. Dr. Tompkin quickly examined the injured guard.

"Dooley got a severe blow on his head. We'll take him to the hospital at once. Probably have to operate."

"That's dreadful!" Mrs. Gruen spoke up.

"Indeed it is, ma'am," said one of the remaining men, who introduced himself as Erman. "And so is all crime. Suppose we go into the house and you tell me what happened here."

Hannah quickly made hot chocolate. As the group sipped it and ate some cookies, Nancy, her father, and the housekeeper told what they knew about the case.

"This sure is a strange one," Erman said. "Of course the thing to do is track down the take-off point of the copter. I'll check with the chief to see if he's put anyone on that angle. Otherwise we'll start right on it." The two men arose, thanked Mrs. Gruen for the hot chocolate, and said good night.

After Mr. Drew had closed the front door, he smiled fondly at Nancy. "That plan to track the copter was your idea too, wasn't it?"

Nancy nodded. Then, on a hunch, she changed the subject. "Dad, you never finished telling me about the glowing eye."