Theory, thought Gan, always theory. The folk of the surface, a million or more years ago, could see the Universe, could sense it directly. Now, with eight hundred miles of rock above their heads, the Race could only make deductions from the trembling needles of their instruments.

It was only theory that brain cells, in addition to their ordinary electric potentials, radiated another sort of energy altogether. Energy that was not electromagnetic and hence not condemned to the creeping pace of light. Energy that was associated only with the highest functions of the brain and hence characteristic only of intelligent, reasoning creatures.

It was only a jogging needle that detected such an energy field leaking into their cavern, and other needles that pin-pointed the origin of the field in such and such a direction ten light-years distant. At least one star must have moved quite close in the time since the surface folk had placed the nearest at five hundred light-years. Or was theory wrong?

"Are you afraid? Gan burst into the conversational level of thought without warning and impinged sharply on the humming surface of Roi's mind.

Roi said, "It's a great responsibility."

Gan thought, "Others speak of responsibility." For generations, Head-Tech after Head-Tech had been working on the Resonizer and the Receiving Station and it was in his time that the final step had to be taken. What did others know of responsibility.

He said, "It is. We talk about Racial extinction glibly enough, but we always assume it will come someday but not now, not in our time. But it will, do you understand? It will. What we are to do today will consume two thirds of our total energy supply. There will not be enough left to try again. There will not be enough for this generation to live out its life. But that will not matter if you follow orders. We have thought of everything. We have spent generations thinking of everything."

"I will do what I am told," said Roi.

"Your thought field will be meshed against those coming from space. All thought fields are characteristic of the individual, and ordinarily the probability of any duplication is very low. But the fields from space number billions by our best estimate. Your field is very likely to be like one of theirs, and in that case, a resonance will be set up as long as our Resonizer is in operation. Do you know the principles involved?"

"Yes, sir."

"Then you know that during resonance, your mind will be on Planet X in the brain of the creature with a thought field identical to yours. That is not the energy-consuming process. In resonance with your mind, we will also place the mass of the Receiving Station. The method of transferring mass in that manner was the last phase of the problem to be solved, and it will take all the energy the Race would ordinarily use in a hundred years."

Gan picked up the black cube that was the Receiving Station and looked at it somberly. Three generations before it had been thought impossible to manufacture one with all the required properties in a space less than twenty cubic yards. They had it now; it was the size of his fist.

Gan said, "The thought field of intelligent brain cells can only follow certain well-defined patterns. All living creatures, on whatever planet they develop, must possess a protein base and an oxygen-water chemistry. If their world is livable for them, it is livable for us."

Theory, thought Gan on a deeper level, always theory. He went on, "This does not mean that the body you find yourself in, its mind and its emotions, may not be completely alien. So we have arranged for three methods of activating the Receiving Station. If you are strong-limbed, you need only exert five hundred pounds of pressure on any face of the cube. If you are delicate-limbed, you need only press a knob, which you can reach through this single opening in the cube. If you are no-limbed, if your host body is paralyzed or in any other way helpless, you can activate the Station by mental energy alone. Once the Station is activated, we will have two points of reference, not one, and the Race can be transferred to Planet X by ordinary teleportation."

"That," said Rois "will mean we will use electromagnet energy."

"And so?"

"It will take us ten years to transfer."

"We will not be aware of duration."

"I realize that, sir, but it will mean the Station will remain on Planet X for ten years. What if it is destroyed in the meantime?"

"We have thought of that, too. We have thought of everything. Once the Station is activated, it will generate a para-mass field. It will move in the direction of gravitational attraction, sliding through ordinary matter, until such time as a continuous medium of relatively high density exerts sufficient friction to stop it. It will take twenty feet of rock to do that. Anything of lower density won't affect it. It will remain twenty feet underground for ten years, at which time a counterfield will bring it to the surface. Then one by one, the Race will appear."

"In that case, why not make the activation of the Station automatic? It has so many automatic attributes already-"

"You haven't thought it through, Roi. We have. Not all spots on the surface of Planet X may be suitable. If the inhabitants are powerful and advanced, you may have to find an unobtrusive place for the Station. It won't do for us to appear in a city square. And you will have to be certain that the immediate environment is not dangerous in other ways."

"What other ways, sir?"

"I don't know. The ancient records of the surface record many things we no longer understand. They don't explain because they took those items for granted, but we have been away from the surface for almost a hundred thousand generations and we are puzzled. Our Techs aren't even in agreement on the physical nature of stars, and that is something the records mention and discuss frequently. But what are "storms."

"earthquakes," "volcanoes."

"tornadoes."

"sleet," "landslides."

"floods."

"lightning," and so on? These are all terms which refer to surface phenomena that are dangerous, but we don't know what they are. We don't know how to guard against them. Through your host's mind, you may be able to learn what is needful and take appropriate action."

"How much time will I have, sir?"

"The Resonizer cannot be kept in continuous operation for longer than twelve hours. I would prefer that you complete your job in two. You will return here automatically as soon as the Station is activated. Are you ready?"

"I'm ready," said Roi.

Gan led the way to the clouded glass cabinet. Roi took his seat, arranged his limbs in the appropriate depressions. His vibrissae dipped in mercury for good contact.

Roi said, "What if I find myself in a body on the point of death?"

Gan said as he adjusted the controls, "The thought field is distorted when a person is near death. No normal thought field such as yours would be in resonance." Roi said, "And if it is on the point of accidental death?" Gan said, "We have thought of that, too. We can't guard against it, but the chances of death following so quickly that you have no time to activate the Station mentally are estimated as less than one in twenty trillion, unless the mysterious surface dangers are more deadly than we expect... You have one minute."

For some strange reason, Roi's last thought before translation was of Wenda,