THE DANCING GREEN BLIP traced an erratic course upon the glossy gray screen, the jagged-line pattern repeated over and over, its outline going from dim to sharply emerald brightness to dim again before fading. The technician cut the switch. There was a sustained whir of reorganization within the machine as the data-cards were refiled.
“Care to see it again, sir?” asked the technician. His fingers hovered over the dials, his body in an attitude of impending motion.
Jerry Norcriss tilted his head in a brief, authoritative nod. The technician started the machine again. With a soft humming, the gray circular screen began to pulse once more with that dancing line of brightness.
“Now, here, sir,” said the tech, “is where the scanner beam first caught the pulse of the creature.”
Jerry nodded, his eyes riveted to that zigzag phosphor pattern upon the screen. He noted the soaring peaks and plunging valleys with something like dismay. “It’s a powerful one,” he marveled. It was one of his rare comments. Space Zoologists rarely spoke at all, to any but their own kind, and even then were typically terse of speech.
The tech, almost as impressed by this—for Jerry—long speech as he had been by the first warning from Naval Space Corps Headquarters on Earth, could only nod grimly. His own eyes were as intent upon the screen as Jerry’s.
“Here—” the line was glowing its brightest now—"here’s where the creature passed directly beneath the scanner-beam. That’s the full strength of its life-pulse.” The line lost clarity and strength, faded. “And here’s where it was lost again, sir.”
“Time of focus?” snapped Jerry, trying to keep his voice calm.
“Nearly a full minute,” said the tech, still blinking at the screen. It was now devoid of impulse, barren once more. “That means that whatever the thing is, it’s big, sir. Damned big, to stay at maximum pulse that long.”
“I know very well what it means!” Jerry grated. “The thing’s so—”
The tech smiled bleakly. “—incredible, sir?”
Jerry’s nod was thoughtful. “The only word for it, Ensign.” His inner eye kept repeating for him that impossible green pattern he’d seen. The strong, flat muscles of his shoulders and neck knotted into what could easily become a villainous tension-headache. Jerry realized suddenly that he was badly scared....
“Sir,” the tech said suddenly, “I was under the impression that the roborocket scanners couldn’t miss a life-pulse on a planet. I mean, making a complete circuit of the planet every ninety minutes, for a period of six months.... It’s impossible for them to miss an uncatalogued life-form.”
“I know it is,” said Jerry Norcriss, pushing blunt fingers through his shock of prematurely white hair. “Save for two precedents, I cannot conceive of any way in which this pulse could have been overlooked.”
“Two precedents, sir?” said the tech, intrigued both by the unsuspected fallibility of the scanner and by this unusual loquacity from the zoologist.
Jerry removed his gaze from the screen and regarded the young man standing beside it. He made as if to reply, then thought better of it. Any out-going on his part was an effort. A big effort. And a danger. Only another Space Zoologist would understand the danger of speech, of letting loose, of relaxing for a moment that terrible vigil over one’s personal psychic barricades.
“Skip it,” he said abruptly. The young ensign’s smile tightened to obedience at the words.
“Yes, sir,” said the tech, with strained cordiality. “Will that be all, sir?”
“Yes,” said Jerry. Then, as the tech started out of the compartment, “No, wait. Tell Ollie Gibbs in the Ward Room to bring up a pot of coffee. Black.”
The man nodded, and went out the door, dogging it after him.
Jerry listened to the booted feet clanking on their magnetic soles up the passageway of the spaceship, and sighed.
The situation, in Jerry’s experience, was fantastic. Only twice, in the history of Space Zoology, had there been oversights on the part of the scanners. One, almost comically, had been on Earth, when the scanners were first being tested. The chunky roborocket—its angles and bulges and tapering pickup-heads unsuitable for flight in any medium but airless space—had swept giddily about the planet, the sensitive pickup-heads recording and filing on microtape the patterns of the life-pulses of all sentient life below. And when the tape had been translated onto the IBM cards, and the cards run through the translation chambers, to get their incomprehensible sine-patterns changed into readable English, it was found that there was an animal missing.
Six months of circling the planet had still left the index blank on that animal’s expected check-pattern. The animal was the brown bear, of north central America. And only after agonizing hours of theorizing and worrying did someone come up with the answer to the dilemma:
It had been a long, hard winter. The bears were in extended hibernation. Somehow, the fleeting flicker of their subdued life-pulses had never managed to correspond with the inquisitive sweep of the scanner-beams from the blackness of space overhead. And so, they’d been left off, as though they did not even exist.
A lot of sweat was dabbed from relieved foreheads in the Corps when a secondary roborocket, sent into a short one-week orbit, had picked up the animals’ pulses with ease as soon as springtime was upon the land. The odds against their being thus missed were fantastic, astronomically unlikely. But it had happened, despite the odds against it, and the Corps was forcibly reminded that in a universe of planets, there is infinite room for even the unlikely to occur.
The only other oversight had been years later, when a just-settling colony had been half-destroyed by a herd of immense beasts similar to the buffalo of Earth, but viciously carnivorous. There had been no indication, in the six-month scanning period, that such a species even existed on the planet, the third planet of Syrinx Gamma, the sun of a newly discovered system beyond the Coalsack.
The reason was maddeningly simple. The herds were migratory. Their migrations had corresponded in scope around the oceanless planet with the sweep of the scanner-beam in such a way that the roborocket was scanning either where the herd had just been or where it had not yet arrived. Again, the odds were fantastic against the occurrence. Yet, again, it had happened. Other than these two events, though, there had been no further error on the part of scanners for nearly a decade.
Precautions had been taken against recurrence.
Roborockets were now sent to scan a planet only at a time when there would be an overlap of seasonal climes, so that the beam would inspect the surface throughout both the mild and the rigorous weathers, thus obviating a repeat of the brown bear incident. And the sweep of the beam had been extended, so that no animal with migratory movement at speeds less than that of a supersonic plane could have avoided being duly detected and catalogued. That, they thought, should prevent any more such incidents.
All that Jerry knew.
And yet, here he was, descending through the black vacuum of space toward an already-colonized planet, the second planet of Sirius, a planet supposedly already scanned, catalogued, and long-since ready for inhabitation. And now, after the colonials had been there for nearly five years, something was starting to wipe them out. Some unsuspected alien thing was present on the planet, a thing that a hastily lofted roborocket had located in a matter of hours, and yet had missed in its original six-month orbital check, before the settlers came.
It was impossible. Incredible. And yet, again, it had happened—was