At the horizon there was a faint glow. Street-lights still burned in the planet's capitol city, but though buildings rose against the sky no lights burned in them. It was not wise for anybody to burn lights that could be seen outside their dwellings. There were police, to be sure. But they were all in Government Center, marshaled there to try to hold a perimeter formed by bricked-up apartment buildings. But much the most of the city was dark and terribly empty save for mobs of all sizes but all raging. Nine-tenths of the city was at the mercy of the paras. Families darkened their homes and terrifiedly hid in corners and in closets, listening for outcries or the thunderous tramping of madmen at their doors.
In the Med Ship the loudspeaker went on.
"—I have told you," said the rounded tones of the planetary president—but his voice shook—"I have told you that Doctor Lett has perfected and is making a vaccine which will protect every citizen and cure every para. You must believe me, my fellow-citizens. You must believe me! To paras, I promise that their fellows who were not afflicted with the same condition—I promise that they will forget! I promise that no one will remember what—what has been done in delirium! What has taken place—and there have been tragedies—will be blotted out. Only be patient now! Only—"
Calhoun went over his glass slides again while the computer stood motionless, apparently without life. But he had called for it to find, in its memory-banks, an organic compound of such-and-such a crystalline form, such-and-such a diffusion rate, such-and-such a specific gravity, and such-and-such a refractive index. Men no longer considered that there was any effective limit to the number of organic compounds that were possible. The old guess at half a million different substances was long exceeded. It took time even for a computer to search all its microfilmed memories for a compound such as Calhoun had described.
"It's standard practice," said Calhoun restlessly, "to consider that everything that can happen, does. Specifically, that any compound that can possibly exist, sooner or later must be formed in nature. We're looking for a particular one. It must have been formed naturally at some time or another, but never before has it appeared in quantity enough to threaten a civilization. Why?"
Murgatroyd licked his right-hand whiskers. He whimpered a little—and Murgatroyd was a very cheerful small animal, possessed of exuberant good health and a fine zest in simply being alive. Now, though, he did not seem happy at all.
"It's been known for a long time," said Calhoun impatiently, "that no life-form exists alone. Every living creature exists in an environment in association with all the other living creatures around it. But this is true of compounds, too! Anything that is part of an environment is essential to that environment. So even organic compounds are as much parts of a planetary life-system as—say—rabbits on a Terran-type world. If there are no predators, rabbits will multiply until they starve."
Murgatroyd said, "Chee!" as if complaining to himself.
"Rats," said Calhoun, somehow angrily, "rats have been known to do that on a derelict ship. There was a man named Malthus who said we humans would some day do the same thing. But we haven't. We've taken over a galaxy. If we ever crowd this, there are more galaxies for us to colonize, forever! But there have been cases of rats and rabbits multiplying past endurance. Here we've got an organic molecule that has multiplied out of all reason! It's normal for it to exist, but in a normal environment it's held in check by other molecules which in some sense feed on it; which control the—population of that kind of molecule as rabbits or rats are controlled in a larger environment. But the check on this molecule isn't working, here!"
The booming voice of the planetary president went on and on and on. Memoranda of events taking place were handed to him, and he read them and argued with the paras who had tried to rush the north gate of Government Center, to makes its inhabitants paras like themselves. But the planetary president tried to make oratory a weapon against madness.
Calhoun grimaced at the voice. He said fretfully:
"There's a molecule which has to exist because it can. It's a part of a normal environment, but it doesn't normally produce paras. Now it does! Why? What is the compound or the condition that controls its abundance? Why is it missing here? What is lacking? What?"
The police-frequency speaker suddenly rattled, as if someone shouted into a microphone.
"All police cars! Paras have broken through a building-wall on the west side! They're pouring into the Center! All cars rush! Set blasters at full power and use them! Drive them back or kill them!"
The grid operator turned angry, bitter eyes upon Calhoun.
"The paras—we paras!—don't want to be cured!" he said fiercely. "Who'd want to be normal again and remember when he ate scavengers? I haven't yet, but— Who'd be able to talk to a man he knew had devoured—devoured—" The grid operator swallowed. "We paras want everybody to be like us, so we can endure being what we are. We can't take it any other way—except by dying!"
He stood up. He reached for the blaster Calhoun had put aside when he changed from the clothes he'd worn in the city.
"—And I'll take it that way!"
Calhoun whirled. His fist snapped out. The grid operator reeled back. The blaster dropped from his hand. Murgatroyd cried out shrilly, from his cubbyhole. He hated violence, did Murgatroyd.
Calhoun stood over the operator, raging:
"It's not that bad yet—you haven't yawned once! You can stand the need for monstrousness for a long while yet. And I need you!"
He turned away. The President's voice boomed— It cut off abruptly. Another voice took its place. And this was the bland and unctuous voice of Doctor Lett.
"My friends! I am Doctor Lett. I have been entrusted with all the powers of the government because I, and I alone, have all power over the cause of the para condition. From this moment I am the government. To paras—you need not be cured unless you choose. There will be places and free supplies for you to enjoy the deep satisfactions known only to you. To non-paras—you will be protected from becoming paras except by your own choice. In return, you will obey! The price of protection is obedience. The penalty for disobedience will be a loss of protection. But those from whom protection is withdrawn will not be supplied with their necessities. Paras, you will remember this! Non-paras, do not forget it! . . ." His voice changed. "Now I give an order. To the police and to non-paras. You will no longer resist paras. To paras: you will enter Government Center quietly and peacefully. You will not molest the non-paras you come upon. I begin at once the organization of a new social system in which paras and non-paras must cooperate. There must be obedience to the utmost—"
The grid operator cursed as he rose from the floor. Calhoun did not notice. The computer had finally delivered the answer he had demanded. And it was of no use. Calhoun said tonelessly:
"Turn that off, will you?"
While the grid operator obeyed, Calhoun read and re-read the answer. He had lacked something of good color before, but as he re-read, he grew paler and paler. Murgatroyd got down restlessly from his cubbyhole. He sniffed. He went toward the small locked chest in which Calhoun had put away the plastic container of living scavengers. He put his nose to the crack of that chest's cover.
"Chee!" he said confidently. He looked at Calhoun. Calhoun did not notice.
"This," said Calhoun, completely white. "This is bad! It's—it's an answer, but it would take time to work it out, and we haven't got the time! And to make it and to distribute it—"