Calhoun tried urgently to figure out a synergic combination which might make a man's blood cease to do its work. Perhaps only minute quantities of the dual poison might be needed. It might work as an antivitamin or an antienzyme, or—
The invaders of the city were immune, though. Quite possibly the same antibodies Murgatroyd had produced were responsible for their safety. Somewhere, somebody had very horribly used the science of medicine to commit a monstrous crime. But medicine was still a science. It was still a body of knowledge of natural law. And natural laws are consistent and work together toward that purpose for which the universe was made.
He heard a movement across the clearing. He reached for his blaster. Then he saw what the motion was. It was Kim Walpole, intolerably weary, trudging with infinite effort to where Helen Jons lay. Calhoun heard him ask heavily, "You're all right?"
"Yes, Kim," said the girl softly. "I couldn't sleep. I'm wondering if we can hope."
Kim didn't answer.
"If we live . . ." said the girl yearningly. She stopped.
Calhoun felt that he ought to put his fingers in his ears. The conversation was strictly private. But he needed to be on guard, so he coughed, to give notice that he heard. Kim called to him, "Calhoun?"
"Yes," said Calhoun. "If you two talk, I suggest that you do it in whispers. I'm going to watch in case the man I killed had a companion who might come looking for him. One question, though. If the plague is artificial, it had to be started. Did a ship land here two weeks or a month before your workmen began to be ill? It could have come from anywhere."
"There was no landing of any ship," said Kim. "No."
Calhoun frowned. His reasoning seemed airtight. The plague must have been introduced here from somewhere else!
"There had to be," he insisted. "Any kind of ship! From anywhere!"
"There wasn't," repeated Kim. "We had no off-planet communication for three months before the plague appeared. There's been no ship here at all except from Dettra, with supplies and workmen and that sort of thing."
Calhoun scowled. This was impossible. Then Helen's voice sounded very faintly. Kim made a murmurous response. Then he said, "Helen reminds me that there was a queer roll of thunder one night not long before the plague began. She's not sure it means anything, but in the middle of the night, with all the stars shining, thunder rolled back and forth across the sky above the city. This was a week or two before the plague. It waked everybody. Then it rolled away to the horizon and beyond. The weather people had no explanation for it."
Calhoun considered. Murgatroyd nestled still closer to him. He snapped his fingers suddenly.
"That was it!" he said savagely. "That's the trick! I haven't all the answers, but I know some very fine questions to ask now. And I think I know where to ask them."
He settled back. Murgatroyd slept. There was the faintest possible murmur of voices where Kim Walpole and the girl Helen talked wistfully of the possibility of hope.
Calhoun contemplated the problem before him. There were very, very few survivors of the people who belonged in the city. There was a shipload of murderers—butchers!—who had landed to see that the last of them were destroyed. Undoubtedly there was a highly trained and probably brilliant microbiologist in the invaders' expedition. One would be needed, to make sure of the success of the plague and to verify the absolute protection of the butchers, so that other colonists could come here to take over and use the planet. There could be no failure of protection for the people not of Dettra who expected to inhabit this world. There would have to be completely competent supervision of this almost unthinkable, this monstrous stealing of a world.
"The plague would probably be a virus pair," muttered Calhoun. "Probably introduced and scattered by a ship with wings and rockets. It'd have wings because it wouldn't want to land, but did want to sweep back and forth over the city. It'd drop frozen pellets of the double virus culture. They'd drop down toward the ground, melting and evaporating as they fell, and they'd flow over the city as an invisible, descending blanket of contagion coating everything. Then the ship would head away over the horizon and out to space on its rockets. Its wings wouldn't matter out of atmosphere and it'd go into overdrive and go back home to wait . . ."
He felt an icy anger, more savage than any rage could be. With this technique, a confederation of human beings utterly without pity could become parasitic on other worlds. They could take over any world by destroying its people, and no other people could make any effective protest, because the stolen world would be useless except to the murderers who had taken it over. This affair on Maris III might be merely a test of the new ruthlessness. The murderer planet could spread its ghastly culture like a cancer through the galaxy.
But there were two other things involved beside a practice of conquest through murder by artificial plagues. One was what would happen to the people—the ordinary, commonplace citizens—of a civilization which spread and subsisted by such means. It would not be good for them. In the aggregate, they'd be worse off than the people who died.
The other?
"They might make a field test of their system," said Calhoun very coldly, "without doing anything more serious to the Med Service than killing one man—me—and destroying one small Med Ship. But they couldn't adopt this system on any sort of scale without destroying the Med Service first. I'm beginning to dislike this business excessively!"
V
"Very much of physical science is merely the comprehension of long-observed facts. In human conduct there is a long tradition of observation, but a very brief record of comprehension. For example, human lives in contact with other human lives follow the rules of other ecological systems. All too often, however, a man imagines that an ecological system is composed only of things, whereas such a system operates through the actions of things. It is not possible for any part of an ecological complex to act upon the other parts without being acted upon in its turn. So that it follows that it is singularly stupid—but amazingly common—for an individual to assume human society to be passive and unreactive. He may assume that he can do what he pleases, but inevitably there is a reaction as energetic as his action, and as well-directed. Moreover, probability . . ."
Probability and Human Conduct—Fitzgerald
An hour after sunrise Calhoun's shoulder pack was empty of food. The refugees arose, and they were weak and ravenous. Their respiration had slowed to normal. Their pulses no longer pounded. Their eyes were no longer dull, but very bright. But they were in advanced states of malnutrition, and now were aware of it. Their brains were again receiving adequate oxygen and their metabolism was at normal level—and they knew they were starving.
Calhoun served as cook. He trudged to the spring that Helen described. He brought back water. While they sucked on sweet tablets from his rations and watched with hungry eyes, he made soup from the dehydrated rations he'd carried for Murgatroyd and himself. He gave it to them as the first thing their stomachs were likely to digest.