Old Thak watched fondly as the new telescope was being put into its place. He had been a long time persuading the elders to build this instrument, a duplicate of the one destroyed in the latest great war. It was as fine a telescope as Mars could produce, and only Thak's assurances that the work was of the greatest importance had secured him this luxury.

His project must succeed, he felt, glancing at his students. Like him, they were almost spherical in shape, with fine arm-like appendages ringing their middles. They were young and enthusiastic, and Thak believed they could revive the science of astronomy. He, the last astronomer of Mars, would teach them all he knew.

The overseer of the workers was disgusted. "You waste our resources, Thak," he declared. "You have taken two years of labor by dozens of workers, and for what? So that you may look at the sky!"

Thak's tentacles purpled, a sign of irritation. "You military men!" he retorted. "It was your kind, Mitfpa, that destroyed our civilization and reduced our race to a few hungry thousands. You have ruined progress and science forever. You have hastened the death of our race. Unless—"

He waved through the open doorway, pointing out the early evening sky. Just rising over the horizon was a blue body that was of a dazzling brilliance, outshining all the other heavenly bodies. Thak's voice became emotional.

"On that planet," he said, "are civilized beings. They hold the only hope for the salvation of our race. We must work to contact them, as long as there is one of us to carry on!"

"What is this, Thak?" Mitfpa demanded angrily. "How can you say, old one, that people of intelligence live on the blue planet? You will tell me next that you have been there!"

The soldier laughed scornfully, but Thak's voice was unruffled as he explained. "This is no mere fancy of mine. These people have been signalling to us for some time. And when I signalled back by creating a network of space-warping lines through our entire power system, they strengthened their signals. Then came your war—"

"Space warps?" Mitfpa growled. "More power wasted? How was this accomplished?"

The workers were bolting the last legs of the telescope into position, and the students were making happy squeaks. Thak looked gratefully toward his new instrument, and toward the scholars. A fine lot of young ones, these. Perhaps, in them, astronomy would become once more a science of great importance. Perhaps they would be the salvation of Mars.

He answered Mitfpa's questions. "The power used was very small. You have heard of controlled space warps?"

"What about it?" grumbled the soldier.

"An interesting laboratory trick. But it also occurs in nature. As a youth I once saw the light of stars bent around the sun in a selector-scope; indeed, it was this very phenomenon that showed our scientists how to make their own warps."

"Enough of your lecture, old one. What was the result of this scientific trickery?"

"One as stupid as you would not understand the method," Thak replied levelly, "but the result of warping all of our power beams was a network of opaque lines that to an observer would be an obvious signal. And now, if you are quite ready to leave—?"

Grumbling, Mitfpa departed, taking his soldier-worker with him. Thak checked the placement of the telescope, finally nodding in satisfaction as he found everything in proper order. The four students crowded around, watching with interest. He gazed good-naturedly at them.

"Our work is a great one," he declared. "We must communicate with the third planet by means of a system of signals that we shall work out—in time. But there is so little time...." His tentacles curled thoughtfully about him. "You have followed the work of our last great physicist, Mor Gran?"

"You mean," asked an alert youngster named Rofan, "the probability tables worked out by him? Showing that the end is near for our race?"

Thak nodded sadly. "Indeed, lad, the future appears dark. War and its disorganization must inevitably strangle civilization. Even now our race is thinned in numbers, and the beasts of the desert multiply."

"There," he went on, waving toward the blue planet, "is our only hope. If we can effect communication with them, and be guided by their superior wisdom, we may yet rally. They may have some secret—some way to prevent wars—"

"There!" Thak said. "There lies our only hope."

"You continue to speak of their superior wisdom, Mor Thak," said Rofan. "How can you be so very sure of that?"

"It is obvious, lad. Their signal system consists of spots of light over the greater part of the land surface of their planet. I have shown you the old photographs, taken before the last war, showing these lights. Even with the small telescope I have been forced to use during these lean years, I have watched the lights. What a mighty science theirs must be that can make the night time light merely to signal another planet! For that can be the only purpose of the lights."

Rofan let his tentacles curl about him as he concentrated. "You must be right," he finally agreed. "I was going to suggest that they might be the lights of cities. I noticed many of them were situated where a city would be likely—but there must be millions of beings to populate so many cities—"

One of the other pupils made a loud amused noise. "Whoever heard of a city without a roof?" he demanded. "Could lights be seen through a roof?"

Rofan was embarrassed, and he remained very quiet for a while, wondering how he could have made such a stupid error. Of course lights could not be seen through a roof. And who had ever heard of a city without a roof!

Thak, paying no attention to the byplay, focused his lens with great care. The students gathered about the concave bowl of white quartz. The lights were lowered, and into the bowl moved a blurred sphere. As Thak's tentacles moved the lenses closer and closer into focus, the sphere resolved itself with more and more clarity, until it was a fine image of the third planet.

Awed by the splendor of the sight, the students could only stare. And indeed it was a breathtaking spectacle, as if they were gathered in the immense void of space itself, looking at the planet from a height of several thousand miles.

There were five continents in two major land masses, Thak had told them. In addition, there were several islands of great size, at last one being practically of continental dimensions, besides a host of islands large and small which dotted the surface of the planet.

The hemisphere on which they gazed was mostly water. The larger land mass was passing from sight. And half of the smaller mass was presented to their vision, a double continent that spread almost from pole to pole, with a narrow isthmus joining north and south.

Like all Martians, they thrilled to a scene of fearful beauty, and they stood around the quartz bowl for a long time, not speaking, merely watching the twin continents come into full view. None noticed old Thak's eyes peering desperately at the image of the third planet. Nor did they see the look of utter despair that grew in his face. They were too intent on the strange scene.

It was Rofan who first felt that something was wrong. The novelty was wearing off, and an elusive thought made him uncomfortable. Something was wrong with the picture ... what was it?

Suddenly he realized. He turned to Thak. "But—the lights, Mor Thak? The signals—"

Thak's face looked as old as Mars itself as he gazed at his pupil. He started to speak several times before he could manage.

"We have failed," he said, in heavy tones. "Our signals must have been too weak for the beings of the blue planet to detect. I had hoped—"

He arose and looked sadly into the evening sky. "I had hoped I was wrong. For two years now—our years—I have watched through my small telescope, and the lights have been disappearing, one by one, sometimes, but more often several at a time. I thought it was the weakness of my instrument. I was wrong. Every light on the blue planet has been blacked out..."

His voice was a low wail. "And—the blacking out of those lights means a blackout of life on Mars. A planet-wide blackout...."