The sky was empty, as empty as if there had never been a Hellhound ship. There was no sign of the fifth-dimensional mass, no hint of ship or gun — just the blue of the sky, ashing into violet as the three suns swung below the far-off horizon.

"Well," said Herb, and Gary could hear his voice sobbing with excitement, "that's the end of the Hellhounds."

Yes, that was the end of the Hellhounds, thought Gary. There was nothing in the universe that could stand before such a blast of energy. When the light, the tiny, feeble beam from the ridiculous little flash had struck the energy field, the energy, that timeless, formless stuff, had suddenly crystallized, had taken on the form of the energy that it had encountered. And in a burst of light it had struck at the Hellhounds, struck with terrible effectiveness — with entire lack of mercy, had wiped them out in the winking of one's eye.

He tried to imagine that blast of light moving out into the universe. It would travel for years, would flash its merciless way for many thousands of light-years. In time its energy would wane, would slowly dissipate, would lose some of its power in the vast spaces of intergalactic space. And perhaps the day would come when all its energy would be gone. But meanwhile nothing could stand in its way, nothing could resist it. In years to come great suns might explode into invisible gas as the frightful beam of power reached them and annihilated them and then passed on. And some astronomer, catching the phenomena in his lens, would speculate upon just what had happened.

He turned slowly around and faced Caroline. "How does it feel," he asked, "to win a war?"

The face she turned to him was strained and worn. "Don't say that to me," she said. "I had to do it. They were a terrible race, but they were alive — and there is so little life in this universe."

"You need some sleep," he said.

He saw the tragic lines of her mouth.

"There is no sleep," she said. "No rest at all. We have just started. We have to save the universe. We have to create more and more of the fifth-dimensional frameworks, many of them and larger. To absorb the energy when the universes meet."

Gary started. He had forgotten the approaching universe. So absorbed had they become in ending the Hellhound attack that the edge of the real and greater danger had been dulled.

But now, brought back to it, he realized the job they faced.

He spun on the Engineer. "How much longer?" he asked. "How much longer have we?"

"Very little time," said the Engineer. "Very little. I fear that energy may flood in upon us at any time."

"That energy," said Kingsley, a fanatical flame in his eyes. "Think of what could be done with it. We could set up a huge framework of fifth-dimensional space, use it as an absorber, a battery. We could send energy almost anywhere throughout the universe. A central universal power plant."

"First," declared Tommy, "you'd have to control it, be able to direct it in a tight beam."

"First," insisted Caroline, "we have to do something about this other universe."

"Wait a second," said Gary. "We've forgotten something. We asked those people in the other universe to come over and help us, but we don't need them now."

He looked at the Engineer. "Have you heard from them?" he asked.

"Yes," said the Engineer. "I have heard from them. They still want to come."

"They still want to come?" Astonishment rang in Gary's voice. "Why should they want to come?"

"They want to emigrate to our universe," said the Engineer. "And I have agreed to allow them to do so."

"You have agreed?" rumbled Kingsley. "And since when has this universe been in the market for immigrants? We don't know what kind of people they are. They might be dangerous. They may want to destroy the present life within the universe."

"There is plenty of room for them," said the Engineer, and if possible, his voice seemed colder and more impersonal than ever. "There is room to spare. We have over fifty billion galaxies — and more than fifty billion stars in each galaxy. Only one out of every ten thousand of the stars has a solar system, that is true, of course… but only one out of every hundred solar systems has life. And if we need more solar systems we can manufacture them. With the power of the dimension of eternity at our command, we can move stars, we can hurl them together to make solar systems. With this power we can reshape the universe, mold it to our needs."

The idea impacted with stunning force on Gary's brain. They could reshape the universe! Working with the raw materials at hand, with the almost infinite power at their command, they could alter the course of stars, could realign the galaxies, could manufacture planets, set up a well coordinated plan to offset entropy, the tendency to run down, the tendency to go amuck. His mind groped futilely at the ideas, pawing them over and over, but back of it all was a curtain of wonderment and awe. And through his brain sang a subtle warning… a persistent little warning that hammered at his thoughts. Mankind itself wasn't ready for such power, couldn't use it intelligently, perhaps would destroy the universe with it. Was there any other entity in the universe qualified to use it? Would it be wise to place such power in the hands of any entity?

"But why," Caroline was asking, "do they want to come?"

"Because," said the Engineer, "we are going to destroy their universe to save ours."

It was as if a bombshell had been dropped among them. Silence clapped down. Gary felt Caroline's hand creep into his. He held it tight.

"But why destroy their universe?" shouted Tommy. "We have the means at hand to save them both. All we have to do is create more of those five-dimensional screens to absorb the energy."

"No," said the Engineer, "we cannot do it. Given time, we could. But there is so little time, not nearly enough. The energy would overwhelm us once it came. It would take so many screens and we have so little time."

His thoughts cut off and Gary heard the shuffle of Kingsley's feet.

"These other beings," the Engineer went on, "know that their universe has very little longer to exist in any event. It has almost reached the end of its time. It soon will die the heat death. Throughout its space, matter and energy are being swiftly distributed. Soon the day will arrive when it will be equally distributed, when the heat, the energy, the mass throughout the universe will be spread so thin that it scarcely exists."

Gary sucked in his breath. "Like a watch running down," he said.

"You're right," said Kingsley. "Like a watch that has run down. That is what will happen to our universe in time."

"Not," said Gary, "if we have the energy from interspace at our command."

"Already," said the Engineer, "only one corner of this other universe is still suitable for life… the area that is facing us. Into that corner all life has been driven and now it has been, or is being, assembled to transfer itself to our universe."

"But," asked Herb, "just how are they going to get here?"

"They will use a time warp," said the Engineer. "They will bud out from their universe, but in doing so they will distort the time factor in the walls of their hypersphere — a distortion that will send them ahead in time, will push their little universe closer to us than to their universe. Our gravity will grasp their hypersphere and draw it in."