They had learned caution on the last planet, and aft carefully considering all the possibilities remained high in the atmosphere while they sent the robot down to investigate. Through its eyes, they saw one of the hemispheres approach until the robot was floating only a few feet awa from the completely smooth featureless surface.
There was no sign of any entrance, nor any hint of the pur pose which the structure served. It was quite large– a hundred feet high; some of the other hemispheres we larger still. If it was a building, there appeared to be no wa in or out.
After some hesitation, Alvin ordered the robot to move forward and touch the dome. To his utter astonishment, it refused to obey him. This indeed was mutiny-or so at sight it seemed.
«Why won’t you do what I tell you?» asked Alvin, wh he had recovered from his astonishment.
«It is forbidden,» came the reply.
«Forbidden by whom?»
«I do not know.»
«Then how-no, cancel that. Was the order built into you?»
«No.»
That seemed to eliminate one possibility. The builders of these domes might well have been the race who made the robot, and might have included this taboo in the machine’s original instructions.
«When did you receive the order?» asked Alvin.
«I received it when I landed.»
Alvin turned to Hilvar, the light of a new hope burning in his eyes.
«There’s intelligence here! Can you sense it?»
«No,» Hilvar replied. «This place seems as dead to me as the first world we visited.»
«I’m going outside to join the robot. Whatever spoke to it may speak to me.»
Hilvar did not argue the point, though he looked none too happy. They brought the ship to earth a hundred feet away from the dome, not far from the waiting robot, and opened the air lock.
Alvin knew that the lock could not be opened unless the ship’s brain had already satisfied itself that the atmosphere was breathable. For a moment he thought it had made a mistake-the air was so thin and gave such little sustenance to his lungs. Then, by inhaling deeply, he found that he could grasp enough oxygen to survive, though he felt that a few minutes here would be all that be could endure.
Panting hard, they walked up to the robot and to the curving wall of the enigmatic dome. They took one more stepthen stopped in unison as if hit by the same sudden blow. In their minds, like the tolling of a mighty gong, had boomed a single message:
That was all. It was a message not in words, but in pure thought. Alvin was certain that any creature, whatever its level of intelligence, would receive the same warning, in the same utterly unmistakable fashion-deep within its mind.
It was a warning, not a threat. Somehow they knew that it was not directed against them; it was for their own protection.
Here, it seemed to say, is something intrinsically dangerous, and we, its makers, are anxious that no one shall be hurt through blundering ignorantly into it.
Alvin and Hilvar stepped back several paces, and looked at each other, each waiting for the other to say what was in his mind. Hilvar was the first to sum up the position.
«I was right, Alvin,» he said. «There is no intelligence here. That warning is automatic-triggered by our presence when we get too close.»
Alvin nodded in agreement.
«I wonder what they were trying to protect,» he said.: «There could be buildings-anything-Under these domes.»
«There’s no way we can find out, if all the domes warn us off. It’s interesting-the difference between the three planets we’ve visited. They took everything away from the first-they abandoned the second without bothering about it -but they went to a lot of trouble here. Perhaps they expected to come back some day, and wanted everything to be ready for them when they returned.»
«But they never did-and that was a long time ago.»
«They may have changed their minds.»
It was curious Alvin thought, how both he and Hilvar had unconsciously started using the word «they.» Whoever or whatever «they» had been, their presence had been strong on that first planet-and was even stronger here. This was a world that had been carefully wrapped up, and put away until it might be needed again.
«Let’s go back to the ship,» panted Alvin. «I can’t breathe properly here.»
As soon as the air lock had closed behind them, and they were at ease once more, they discussed their next move. To. make a thorough investigation, they should sample a large number of domes, in the hope that they might find one that had no warning and which could be entered. If that failed Alvin would not face that possibility until he had to.
He faced it less than an hour later, and in a far more dramatic form than he would have dreamed. They had sent: the robot down to half a dozen domes, always with the same, result, when they came across a scene that was badly out of place on this tidy, neatly packaged world.
Below them was a broad valley, sparsely sprinkled with’ the tantalizing, impenetrable domes. At its center was the unmistakable scar of a great explosion-an explosion that had thrown debris for miles in all directions and burned a shallow crater in the ground.
And beside the crater was the wreckage of a spaceship.
Twenty-one
They landed close to the scene of this ancient tragedy and walked slowly, conserving their breath toward mense, broken hull towering above them. Only a short section -either the prow or the stern-of the ship remained; presumably the rest had been destroyed in the explosion. As they approached the wreck, a thought slowly dawned in Alvin’s mind, becoming stronger and stronger until it attained the status of certainty.
«Hilvar,» he said, finding it hard to talk and walk at the same time, «I believe this is the ship that landed on the first planet we visited.»
Hilvar nodded, preferring not to waste air. The same idea had already occurred to him. It was a good object lesson, he thought, for incautious visitors. He hoped it would not be lost on Alvin.
They reached the hull and stared up into the exposed interior of the ship. It was like looking into a huge building that had been roughly sliced in two; floors and walls and ceilings, broken at the point of the explosion, gave a distorted chart of the ship’s cross section. What strange beings, wondered Alvin, still lay where they had died in the wreckage of their vessel?
«I don’t understand this,» said Hilvar suddenly. «This portion of the ship is badly damaged, but it’s still fairly intact. Where’s the rest of it? Did it break in two out in space, and this part crash here?»
Not until they had sent the robot exploring again, and had themselves examined the area around the wreckage, did they learn the answer. There was no shadow of doubt; any reservations they might have had were banished when Alvin found the line of low mounds, each ten feet long, on the little hill beside the ship.
«So they landed here,» mused Hilvar, «and ignored the warning. They were inquisitive, just as you are. They tried to open that dome.»
He pointed to the other side of the crater, to the smooth, still unmarked shell within which the departed rulers of this world had sealed their treasures. But it was no longer a dome; it was now an almost complete sphere, for the ground in which it had been set had been blasted away.
«They wrecked their ship, and many of them were killed. Yet despite that, they managed to make repairs and leave again, cutting off this section and stripping out everything of value. What a task that must have been!»
Alvin scarcely heard him. He was looking at the curious marker that had first drawn him to this spot-the slim shaft Pinged by a horizontal circle a third of the way down from its up. Alien and unfamiliar though it was, be could respond to the mute message it had carried down the ages. Underneath those stones, if he cared to disturb them, was the answer to one question at least. It could remain unanswered; whatever these creatures might have been, they had earned their right to rest.