headquarters at the cosmodrome. It was no easy thing to detect the Setaur, a tiny piece of metal in a giant wilderness of rock filled with fields of detritus, cracks, and half-buried crevices, and covered besides with the pockmarks of miniature craters.
If only those reports had at least been negative! But the patrolling crews had alarmed ground personnel several times already with the information that the “mad machine” was sighted. So far it had turned out that the object was some unusual rock formation or a fragment of lava sparkling in the rays of the sun; even the use of radar along with ferroinduction sensors proved to be of little help—in the wake of the first stages of lunar exploration and colonization, there remained upon the Moon’s rocky wastes a whole multitude of metal containers, heat-fused shells from rocket cartridges, and all possible sorts of tin junk, which every now and then became the source of fresh alarms. So much so that operation headquarters began to wish the Setaur would finally attack something and show itself. However, the last time it had revealed its presence was with the attack on the small transporter belonging to the electrical repair team. Since then it seemed as if the lunar soil had opened up and swallowed the thing. But everyone felt that sitting and waiting was out of the question, particularly when Construction had to regain its energy supply.
The mission—covering about ten thousand square kilometers—consisted in combing that area with two waves of vehicles approaching each other from opposite directions, from the north and the south. From Construction came one extended line under the command of their head technologist, Strzibor, and from the Luna Base cosmodrome came the second, in which the role of operations coordinator of both sides, working closely with the chief (Commodore-Navigator Pleydar), fell to Pirx. He understood perfectly that at any moment they could pass right by the Setaur; it might, for example, be hidden in one of those deep tectonic trenches, or even be camouflaged by nothing but the dazzling lunar sand, and they would never notice it; McCork, who rode with him as “intellectronician-consultant,” was of the same opinion.
The transporter lurched dreadfully, moving along at a speed that, as the driver quietly informed them, “after a while makes your eyes pop out.” They were now in the eastern sector of the Sea of Tranquillity and less than an hour away from the region where the automaton was most likely to be located. After crossing that previously determined border, they were all to don their helmets, so that in case of an unexpected hit and loss of seal, or in case of fire, they could leave the vehicle immediately.
The transporter had been changed into a fighting machine; the mechanics had mounted on its domelike turret a mining laser of great power, though pretty poor as far as accuracy went. Pirx considered it altogether useless against the Setaur. The Setaur possessed an automatic sighter, since its photoelectric eyes were hooked up directly to the laser and it could instantly fire at whatever lay in the center of its field of vision. Theirs, on the other hand, was a quaint sort of sighter, probably from an old cosmonautical range-finder; the only testing it had received was when, before leaving Luna Base, they took a few shots at some rocks on the horizon. The rocks had been large, the distance less than two kilometers, and even so they hit the mark only on the fourth try. And here, to make matters worse, you had lunar conditions to cope with, because a laser beam was visible as a brilliant streak only in a diffusing medium, such as an Earthlike atmosphere; but in empty space a beam of light, regardless of how powerful, was invisible until it hit some material obstacle. Therefore, on Earth you could shoot a laser much the way you shot tracer bullets, guided by their observable line of flight. Without a sighter, a laser on the Moon was of no practical value. Pirx didn’t keep this from McCork; he told him when only a couple of minutes separated them from the hypothetical danger zone.
“I didn’t think of that,” said the engineer, then added, with a smile, “Why did you tell me?”
“To free you of illusions,” replied Pirx, not looking up from the double eyepiece of his periscope. It had foam- rubber cushions, but he felt sure that he would be going around with black eyes for the longest time (assuming, of course, he came out of this alive). “And also to explain why we’re carrying that stuff in the back.”
“The cylinders?” asked McCork. “I saw you taking them from the storeroom. What’s in them?”
“Ammonia, chlorine, and some hydrocarbons or other,” said Pirx. “I though they might come in handy.”
“A gas smoke-screen?” ventured the engineer.
“No, what I had in mind was some way of aiming. If there’s no atmosphere, we create one, at least temporarily…”
“I’m afraid there won’t be time for that.”
“Perhaps not, but I brought it along just in case. Against something insane, insane measures are often best.”
They fell silent, for the transporter had begun to lurch like a drunk; the stabilizers whined and squealed, sounding as if at any minute the oil in them would begin to boil. They hurtled down an incline strewn with sharp boulders. The opposite slope gleamed, all white with pumice.
“You know what worries me most?” resumed Pirx when the heaving let up a little; he had grown strangely talkative. “Not the Setaur—not at all—it’s those transporters from Construction. If just one of them takes us for the Setaur and starts blasting away with its laser, things’ll get lively.”
“I see you’ve thought of everything,” muttered the engineer. The cadet, sitting beside the radio operator, leaned across the back of his seat and handed Pirx a scrawled radiogram, barely legible.
“We have entered the danger zone at relay twenty, so far nothing, stop, Strzibor, end of transmission,” Pirx read aloud. “Well, we’ll soon have to put our helmets on, too…”
The machine slowed a little, climbing a slope. Pirx noticed that he could no longer see the neighbor on his left—only the right-hand transporter was still visible, moving like a dim blot up the bank. He ordered that the machine on the left be raised on the radio, but there was no answer.
“We have begun to separate,” he said calmly. “I thought that would happen. Can’t we push the antenna up a little higher? No? Too bad.”
By now they were at the summit of a gentle rise. From over the horizon, at a distance of less than two hundred kilometers, emerged, full in the sun, the sawtooth ridge of the crater Toricelli, sharply outlined against the black background of the sky. They had the plain of the Sea of Tranquillity all but behind them now. Deep tectonic rifts appeared, frozen slabs of magma jutted here and there from under the debris, and over these the transporter crawled with difficulty, first heaving up like a boat on a wave, then dropping heavily down, as though it were about to plunge head over heels into some unknown cavity. Pirx caught sight of the mast of the next relay, glanced quickly at the celluloid map card pressed to his knees, and ordered everyone to fasten their helmets. From now on they would be able to communicate only by intercom. The transporter managed to shake even more violently than before—Pirx’s head wobbled around in its helmet like the kernel of a nut inside an otherwise empty shell.
When they drove down the slope to lower ground, the saw of Toricelli disappeared, blocked out by nearer elevations; almost at the same time they lost their right neighbor. For a few minutes more they heard its call signal, but then that was distorted by the waves bouncing off the sheets of rock. Complete radio silence followed. It was extremely awkward trying to look through the periscope with a helmet on; Pirx thought he would either crack his viewplate or smash the eyepiece. He did what he could to keep his eyes on the field of vision at all times, though it shifted drastically with each lurch of the machine and was strewn with endless boulders. The jumble of pitch-black shadow and dazzlingly bright surfaces of stone made his eyes swim.
Suddenly a small orange flame leaped up in the darkness of the far sky, flickered, dwindled, disappeared. A second flash, a little stronger. Pirx shouted, “Attention everyone! I see explosions!” and feverishly turned the crank of the periscope, reading the azimuth off the scale etched on the lenses.
“We’re changing course!” he howled. “Forty-seven point eight, full speed ahead!”
The terms of this order really applied to a cosmic vessel, but the driver understood it all the same; the plates and every joint of the transporter gave a shudder as the machine wheeled around practically in place and surged forward. Pirx got up from his seat: its tossing was pulling his head away from the eyepiece. Another flash—this time red-violet, a fan-shaped burst of flame. But the source of those flashes or explosions lay beyond the field of vision, hidden by the ridge they were climbing.
“Attention everyone!” said Pirx. “Prepare your individual lasers! Dr. McCork, please go to the hatch. When I give the word, or in case of a hit, you’ll open it! Driver! Decrease velocity!”
The elevation up which the machine was clambering rose from the desert like the shank of some moon monster, half sunken in debris; the rock in fact resembled, in its smoothness, a polished skeleton or giant skull; Pirx ordered the driver to go to the top. The treads began to chatter, like steel over glass. “Hold it!” yelled Pirx, and the transporter, coming to a sudden halt, dipped nose-down toward the rock, swayed as the stabilizers groaned with the strain, and stopped.
