Then she spoke. "They think they are contacting someone else," she said. "Some great civilization that must have lived here at one time. The messages come from far away. From even farther than the Great Nebula. The Nebula just happens to be in the same direction. They are puzzled that we do not answer. They know someone has been trying to answer. They're trying to help us to get through. They talked in scientific terms I could not understand. Something to do with the warping of space and time, but involving principles that are entirely new. They want something and they are impatient. It seems there is a great danger someplace. They think that we can help."

"Great danger to whom?" asked Kingsley.

"I couldn't understand," said Caroline.

"Can you talk back to them?" asked Gary. "Do you think you could make them understand?"

"I'll try," she said.

"All you have to do is think," Kingsley told her. "Think clearly and forcefully. Concentrate all that you can, as if you were trying to push the thought away from you. The helmet picks up the impulses and routes them through the thought projector."

Her slim fingers reached out and turned a dial. Tubes came to life and burned into a blue intensity of light. A soaring hum of power filled the tiny room.

The hum became a steady drone and the tubes were filled with a light that hurt one's eyes.

"She's talking to them now," thought Gary. "She is talking to them."

The minutes seemed eternities, and then the girl reached out and closed the dial. The hum of power receded, clicked off and was replaced by a deathly silence.

"Did they understand?" asked Kingsley, and even as he spoke the light blinked red again.

Kingsley's hand closed around Gary's arm and his harsh whisper rasped in Gary's ear.

"Instantaneous!" he said. "Instantaneous signals! They got her message and they are answering. That means the signals are routed through some extra-dimension."

Swiftly the red light blinked. Caroline crouched forward in the chair, her body tensed with what she heard.

The light blinked off and the girl reached up and tore the helmet off.

"It can't be right," she sobbed. "It can't be right."

Gary sprang forward, put an arm around her shoulder.

"What's wrong?" he asked.

"Those messages," she cried. "They come from the very edge of all the universe… from the farthest rim of exploding space!"

Kingsley leaped to his feet.

"They are like the voices I heard before," she said. "But different, somehow. More kindly… but terrifying, even so. They think they are talking to someone else. To a people they talked to here on Pluto many years ago… I can't know how many, but it was a long, long time ago."

Gary shook his head in bewilderment and Kingsley rumbled in his throat.

"At first," Caroline whispered, "they referred to us by some term that had affection in it… actual kinfolk affection, as if there were blood ties between them and the things they were trying to talk to here. The things that must have disappeared centuries ago."

"Longer ago than that," Kingsley told her. "That the thought bombardment is directed at this spot would indicate the things they are trying to reach had established some sort of a center, perhaps a city, on this site. There are no indications of former occupancy. If anyone was ever here, every sign of them has been swept away. And here there is no wind, no weather, nothing to erode, nothing to blow away. A billion years would be too short a time —»

"But who are they?" asked Gary. "These ones you were talking to. Did they tell you that?"

She shook her head. "I couldn't exactly understand. As near as I could come, they called themselves the Cosmic Engineers. "That's a very poor translation. Not sufficient at all. There is a lot more to it."

She paused as if to marshal a definition. "As if they were self-appointed guardians of the entire universe," she explained. "Champions of all things that live within its space-time frame. And something is threatening the universe. Some mighty force out beyond the universe out where there's neither space nor time."

"They want our help," she said.

"But how can we help them?" asked Herb.

"I don't know. They tried to tell me, but the thoughts they used were too abstract. I couldn't understand entirely. A few clues here and there. They'll have to reduce it to simpler terms."

"We couldn't even get there to help them," said Gary. "There is no way in which we can reach the rim of the universe. We haven't yet gone to the nearest star."

"Maybe," suggested Tommy Evans, "we don't need to get there. Maybe we can do something here to help them."

The red light was blinking again. Caroline saw it and reached for the helmet, put it on her head. The light clicked out and her hand went out and moved a dial. Again the tubes lighted and the room trembled with the surge of power.

Dr. Kingsley was rumbling. "The edge of space. But that's impossible!"

Gary laughed at him silently.

The power was building up. The room throbbed with it and the blue tubes threw dancing shadows on the wall.

Gary felt the cold wind from space again, flicking at his face, felt the short hairs rising at the base of his skull.

Kingsley was jittery. And he was jittery. Who wouldn't be at a time like this? A message from the rim of space! From that inconceivably remote area where time and space still surged outward into that no-man" s-land of nothingness… into that place where there was no time or space, where nothing had happened yet, where nothing had happened ever, where there was no place and no circumstance and no possibility of event that could allow anything to happen. He tried to imagine what would be there. And the answer was nothing. But what was nothing?

Many years ago some old philosopher had said that the only two conceptions which Man was capable of perceiving were time and space, and from these two conceptions he built the entire universe, of these two things he constructed the sum total of his knowledge. If this were so, how could one imagine a place where neither time nor space existed? If space ended, what was the stuff beyond that wasn't space?

Caroline was closing the dials again. The blue light dimmed and the hum of power ebbed off and stopped. And once again the red light atop the machine was blinking rapidly.

He watched the girl closely, saw her body tense and then relax. She bent forward, intent upon the messages that were swirling through the helmet.