But at the moment he was far more intent on those tracks which lured him on, up a gradually narrowing valley towards the mountain walls. The climbing sun stuck across his path, but there were pools of purple shadow where the cliffs walled off its rays.
The trail left by the crawler ran as straight as the general contour of the ground allowed. Two of the lacy winged flying things they had glimpsed in the other valley skimmed close to the surface of the stream and then took off high into the chill air.
Now the greenery was sparser. He had not passed a field for some time. And underfoot the surface of the valley was inclining up in a gentle slope. The walls curved, so that Dane walked more warily, having no desire to round a projection and meet a blaster user face to face.
He was certain in his own mind that Dr. Rich had something to do with this. But where did this crawler come from? Had the Doctor been on Limbo before? Or had he broken into some cache of Survey supplies? But there was Ali’s certainty that the vehicle was not orthodox.
The trail ended abruptly and in such a manner as to stop Dane short, staring in unbelief. For those ruts led straight to a solid, blank wall of rock, vanishing beneath it as if the machine which had made them had been driven straight through!
There is always, Dane hastily reminded himself, some logical explanation for the impossible. And not Video ones about “force walls” and such either. If those tracks went into the rock, it was an illusion—or an opening—and it was up to him to discover which.
His boots crunched on sand and gravel until he was in touching distance of the barrier. It was then that he became aware of something else, a vibration. It was very silent there in the cramped pocket which was the end of the valley, no wind blew, no leaves rustled. And yet there was something unquiet in the air, a stirring just at the far edge of his sensitiveness to sound and movement.
On impulse he set the palms of his hands against the stone of the cliff. And he felt it instantly, running up his arms into his body until his flesh and bones were only a recorder for that monstrous beat-beat-beat—relayed to him through the stuff of Limbo itself. Yet, when he passed his fingers searchingly over the rough stone, studied each inch of it intently, he could see no break in its surface, no sign of a door, no reason for that heavy thump, thump which shook his nerves. The vibration was unpleasant, almost menacing. He snatched his hands away, suddenly afraid of being trapped in that dull rhythm. But now he was sure that Limbo was not what it seemed— a lifeless, dead world.
For the first time he remembered that he should have maintained contact with the others, and hurriedly turned the key on his com-unit. Instantly Tau’s voice rang thinly in his ears.
“Calling Ali—calling Thorson—come in—come in!” There was an urgency in the Medic’s voice which brought Dane away from the wall, set him on the back trail even as he replied:
“Thorson here. Am at end of valley. Wish to report—”
But the other cut into that impatiently. “Return to flitter! Ali, Thorson, return to flitter!”
“Thorson returning.” Dane started at the best pace he could muster down the valley. But as he trotted, slipping and sliding on the loose stones and gravel, Tau’s voice continued to call Ali. And from the engineer-apprentice there came no answer at all.
Breathing hard, Dane reached the place where they had left the Medic. As he came into sight Tau waved him to the side of the flitter.
“Where’s Ali?” “Where’s Kamil?” Their demands came together and they stared at each other.
Dane answered first. “He said he was going down stream—to follow the crawler tracks we found. I went upstream—”
“Then it must have been he who—” Tau was frowning. He turned on his heel and studied the valley leading to the plains. The presence of water had encouraged a thicker growth of brush there and it presented a wall except for where the stream cut a passage.
“But what happened?” Dane wanted to know.
“I got a call on com—it was cut off almost immediately—”
“Not mine, I was off circuit,” returned Dane before he thought. It was only then that he realized what he had done. No one on field duty goes off circuit out on scout, that was a rule even a First Circler in the Pool had by heart. And he had done it the first time he was on duty! He could feel the heat spreading up into his cheeks. But he offered no explanations nor excuses. The fault was his and he would have to stand up to the consequences.
“Ali must be in trouble,” Tau made no other comment as he climbed in behind the controls of the flitter, a very quiet Dane following him.
They arose jerkily, with none of the smooth perfection Ali’s piloting had supplied. But once in the air Tau pointed the nose of the flitter down valley, cutting speed to just enough to keep them airborne. They watched the ground below. But there was nothing to see but the marks of blaster fire and beyond undisturbed green broken by bare patches of gravel and jutting rock.
They could also sight the crawler tracks and Dane related the information he had. Tau’s countenance was sober.
“If we don’t find Ali, we must report to the Queen—”
That was only common sense, Dane knew, but he dreaded having to admit his own negligence. And perhaps his act was worse than just carelessness in not using the com-unit, perhaps he should have insisted on their sticking together, deserted though the valley appeared to be.
“We’re up against something nasty here,” Tau continued. “Whoever used those blasters was outside the law—”
The Federation law dealing with X-Tees was severe, as Dane well knew. Parts of the code, stripped of the legal verbiage, had to be memorized at the Pool. You could defend yourself against the attack of aliens, but on no provocation, except in defence of his life, could a Trader use a blaster or other weapon against an X-Tee. Even sleep rays were frowned upon, though most Traders packed them when going into unknown territory among primitive tribes.
The men of the Queen had landed unarmed on Limbo, and they would continue unarmed until such a time as the situation was so grave that either their lives or the ship was in danger. But in this valley a blaster had been used in the wanton indulgence of someone’s sadistic hatred for the globe creatures.
“They weren’t attacking—those globe things, I mean?”
Tau’s brown face was grim as he shook his head. “They had no weapons at all. I’d say from the evidence that they were attacked without warning, just mown down. Maybe for the fun of it!”
And that projected such a picture of horror that Tau, conditioned by life under the Trade Creed, stopped short.
Below them the valley began to widen out, cutting in a fan shape into the plain. There was no sign of Ali anywhere on that fan. He had vanished as if he had stepped through the cliff wall. The cliff! Dane, remembering the end of the crawler trail, pressed against the windshield to inspect those walls. But there were no tracks ending before them.
The flitter lost altitude as Tau concentrated on landing. “We must report to the Queen,” he said as he set them down. Not leaving his seat he reached for the long-range beam mike.
CHAPTER SEVEN:
SHIP OUT OF SPACE
Tau’s fingers clicked the call key of the far-range caster when that sound was drowned out by a wail, both weirdly familiar and strangely menacing. Here on the edge of the burnt-off land there was no soughing of the wind, nothing to break the eternal silence of the blasted country. But this tearing over head brought both of the Terrans to their feet. Tau, out of his greater experience, identified it first.