"Ages passed, and then down from the north rolled a mighty tide of ice, sweeping over the whole land and submerging all under its frozen flood. It rolled down toward the four cities, and finally had forged south until it was at the gates of the city of cubes. In desperation, the people of the cubes appealed to those in Kom for shelter, and it was granted them. They came down to Kom, every one, and the ice rolled over and hid the city of cubes. Next it engulfed the city of spheres, and its people likewise found refuge in Kom, which was the most southern of all the four cities. And finally, the ice-tide swept over the city of cylinders, and its people, the Kanlars, were forced to seek refuge in Kom also, though they liked it not.

"But the ice did not stop. It came on, ever south, until it threatened to cover Kom also, and leave our people homeless and shelterless. So, taking counsel among themselves, the people of Kom set out to stop the progress of the glacial sheet.

"They kindled great uprisings far beneath the earth's surface, until the tortured earth heaved up in a great wall across the ice-flood's path. And then, that this wall of earth might not be swept away, the scientists of Kom showed them a way by which every kind of material could be transmuted at will into other elements, by a recasting of its electronic structure. And, using this power, the people of Kom smoothed the gigantic barrier they had created, and then, using the instruments their scientists had devised for them, they turned on the great wall a ray that changed it to metal by its power of element-transmutation. It was finished, and when the ice rolled down to this smooth mountain-range of metal, it was checked, halted. Far away, on either side, it rolled on and engulfed the country, but the wall so dammed it that it could not progress farther toward the city.

"Yet the cold of the glacier was not halted by the wall, and to combat that cold, the great shield of force was devised that stretches over all Kom, and into which you crashed in your car. It admitted the sun's light and heat, but excluded the cold winds from the glacier. And thus, having thwarted nature itself, the troubles of the people of Kom were seemingly at an end.

"The people of the other three cities settled down contentedly enough in Kom, and each people built their own type of dwelling, cube or sphere or cylinder. And all mixed, intermarried, and mingled in race, with the exception of the Kanlars, the people of the cylinders. These still held apart, though unobtrusively.

"And as the years went by, the scientists of Kom came to more and more wisdom. They found ways to strengthen their own bodies, so that they lived for great stretches of time, as we do yet. They sent their explorers out to other planets, they cast their vision out to the farthest stars. They learned to create life, and they learned to conquer death, almost. The flight of the soul from the body they could not control, for there is a wisdom above man's, but the body itself they could retain as moving and lifelike as in life itself, though soulless.

"It seemed, indeed, that no other steps of wisdom remained up which to climb. And then, without the knowledge of the other people, the Kanlar scientists set themselves to conquer the secret of time. Unable to find a way of controlling time themselves, of moving in it at will, they created a monstrous, undreamed-of thing, a thing of shapeless, inchoate body, which was yet living, and which could transform itself, at will, into mists and vapors, and in that gaseous form could travel at will through time. And this thing the Kanlars made, setting in it three orbs of light that were its organs of sense and its seat of intelligence, and this thing is the same that you now call the Raider.

"This, indeed, happened in my own lifetime, a scant score of years ago. And when the Kanlars brought their creation before the supreme council of Kom, I was a member of that council.

"They explained the power of their creation, they showed its life, its intelligence. And they proposed to the council a plan which possession of the Raider made possible.

"They pointed out that since the Raider could travel at will through time, it could whirl back into the past, or into the future, and seize people from every age, bringing them back to our own time to be our slaves. Always there had been none but free people in our cities, nor were slaves needed, since nearly all of our work was done by machinery, yet such was the evil plan of the Kanlars.