The Nitrogen Fix

by Hal Clement

  There were no surviving real-life animal forms other than humanity from before the change; and in spite of the nitro-life’s tendency to easy mutation and consequent rapid evolution it had produced no animals much above microscopic size.None of these had developed the ability to parasitize human beings, though some were dangerous to air-cultures and other human necessities.

  Kahvi surfaced at the land end of the raft with all her attention, therefore, directed toward the shore.

  Nothing could be seen or heard but the ripple of waves on the beach, even with the tent tissue no longer in the way. She listened and looked for several minutes, and finally waded ashore. Dimly aided by vision, she found where they had stacked the cargo. It was still there.

  Finally she called out her husband’s name. “ Earrin? Where are you?”

  The answer was not in Fyn’s voice, and she started violently. “He’s not here, Kahvi Mikkonen, but is in no trouble.”

  “Where is he? Why didn’t he tell me he was going? Who are you?”

  “There was some danger, and we took him up to the hill.”

  “What danger? The fire? We thought that was out, and — ”

  “Not the fire. It is out.” The voice, originally some tens of meters away, was coming closer, though Kahvi could not yet see its owner. “I don’t want to frighten you, but your husband was being followed by an Invader.”

  “What’s an Invader? And who are you? I don’t recognize your voice, but — ”

  “But you’ve seen me before. I’m Jem Endrew. I met both of you when you were delivering copper a long time ago. Surely you’ve seen Invaders; you Nomads must meet them far oftener than those of us who live underground. They look like — well maybe you’ve never seen a book with a picture of a fish.”

  There was just a suggestion that the voice had been going to continue, and Kahvi suspected that the Hiller had just stopped himself from adding, “Maybe you’ve never seen a book.”

  “I have,” she replied. “They look a little like the metal-feeders we get your copper from.”

  “I’ve never seen even a picture of those,” Endrew admitted. “Anyway, the Invaders have long bodies, anywhere from half or three quarters of a meter to two and a half or three. They’re fish-shaped, as I said.

  A big one is maybe a third of a meter wide at the widest part, and not quite as thick. The tail goes sideways instead of up and down, and there are two long sort of flaps or fringes along the sides. They swim with a sort of up-and-down bending of the body and flaps and tail. There’s a big eye on each side in front of the flap, and a long ropy arm between the eye and the flap. The mouth goes across the top of the head — or the front, if it’s swimming — and opens sideways, and has little ropy arms around it. There are more of the ropy things in back — I’m not sure just how many. You’d think they were too thin, but the Invader can stand up on them and even run faster than a man. You really haven’t seen one?”

  Kahvi was tempted to evade, but Nomad hangups overrode the urge.

  “Oh, I’ve seen them, of course. We don’t call them — what was it — Invaders. Are they common here? Didn’t you used to call them Animals? I’ve only had a really good look at one of them.” The last statement was a strain; it was the truth, in a way, but certainly a truth likely to deceive.

  “They’re not really common,” replied Endrew. “Yes, they used to be called Animals until we learned better. What do you call them?”

  Again the habit of truthfulness prevailed.

  “Natives.”

  “What? But that’s ridiculous! A native is a — a person who is born in a place, and whose parents and grandparents have been — it’s someone who belongs. How can one of these things belong? We’re the natives!”

  “How can we be?” Kahvi asked in astonishment. “We can’t even live here without special equipment.

  We have to breathe oxygen, and we have to have real or pseudo plants to make that by photosynthesis.

  There aren’t enough of those to make a whole world full of oxygen, and if there were there are too many other plants to take the oxygen and make nitric acid. You’ve been taking your mythology too seriously.

  Calling people natives is simply silly. I suppose we must be natives of somewhere, but it certainly isn’t this world.”

  “That’s right — you probably went to a Surplus school, didn’t you?” sneered the Hiller. “They never told you about the change — that Earth used to have air people could breathe. It was the Invaders who made the change, and destroyed the oxygen.”They taught me the change myths, all right,” retorted Kahvi, “but they claimed it was human beings who made the change with science. I don’t see why I should believe any of the stuff they taught in Surplus school — all they really wanted was to convince me it was right and proper for me to be aborted from Blue Hill on my twelfth birthday.”

  “From Blue Hill? You’re one of our Nomads?”

  “I was born in Blue Hill, the third child of my highly respectable parents, and therefore Surplus.

  You’re a bit young to remember — and of course you wouldn’t have been in contact with such undesirables anyway.”

  She stopped, realizing that her temper had made her say too much. Neither she nor her husband cared greatly about their state of exile — both liked the Nomad life; but they had decided long before that if their “home” cities happened to forget them, trading and other relationships would be more comfortable. Most city-dwellers were more negative about their “own” Nomads than others, for reasons not obvious to either of the Fyn family adults. Presumably Endrew would be the same.

  If he was, though, it didn’t show. There was no change in his tone as he answered, “Thanks for telling me. That must have happened, as you say, before I was old enough to know. Abortions don’t happen very often, after all; the last one was when I was about eight, and that was an older person. I might tell you about that some time, if you don’t mind listening to something besides mythology — and don’t mind risking the discovery that what you think is mythology really happened.”

  “One Surplus school is enough, thanks.” Kahvi was just barely polite. “I must thank you also for telling me about my husband, and trying to protect him from your — Invader, if that’s what you call the natives. I’m sorry you had to wait so long; you could have come to the raft to tell me.”

  “Your husband had already started with the others when I was told to wait to tell you. He said nothing about sharing your air. I had the jail nearby for recharging if I needed to.”

  “Thanks again. I hadn’t realized he went unwillingly.”

  “How do — what makes you think he did?”

  “Something you just told me. I’ll keep the details. I’m not worried about what the ‘Invaders’ might do to Earrin, but I hope he’s safe with your friends. If you don’t need our air, I’ll go back to get some sleep. I will come ashore in the morning to complete whatever arrangements are in order about the cargo — and about my husband. Breathe freely.”

  “Breathe freely.” The dark figure made no attempt to dispute her implied charges, and moved away toward the jail with no further words.

  Back on the raft Kahvi could not sleep, though she couldn’t guess why. She was not really worried about Earrin, in spite of her words to Endrew; she could not really believe that Hillers, or any other city-dwellers, who Nomadded their Surplus children so they could ignore the unpleasant fact of what usually happened to them, would actually resort to violence. What they wanted him for was still unclear, but she expected to see him again unharmed.

  Danna was where she belonged, breathing quietly. The life support plants all smelled as they should — Kahvi got up and checked them again, after a while, as the most likely source of her wakefulness. Bones’ absence was a little unusual, but not really surprising. Kahvi knew enough about her drives to guess that there would be information the next day about what had gone on at the fire site. The fire itself must have been caused by Hillers, since there had been no lightning
in the Boston area for days.

  What did these people want with all that metal and glass? She and Earrin had wondered after receiving the order, but had found no answer which they could believe. There was little use now for either material. Glass furnished smooth surfaces for growing tissue sheets, and of course sharp edges. Copper was mostly used for art work, though it was sometimes hammered into tools which needed no edge, or at least no durable one.

  Earrin had never been inside the Blue Hill city, and the northern one from which he had been aborted had not given him enough knowledge to make good guesses; its Surplus school had been no better than, if as good as, Blue Hill’s. Kahvi knew more about city life, and was better read, than her husband because she had not been Nomadded so young. Most Surplus children, of course, were not ejected; death rates were such that most of them reentered their societies long before reaching the key age oftwelve. Kahvi had made it by only one day, and never really recovered from the tension of the preceding few months. She had hated the school, hated the community, hated her status, and for the most part hated her fellow citizens. The school had, of course tried to make her regard the whole system as natural, inevitable, and right. A city had air for just so many people; if any couple had more than two children, the surplus ones could not be kept unless death made room for them. The guilty parents could not, of course, be dispensed with; they were already useful citizens and real people.

  The Surplus children could not, of course, be destroyed — that would be violence. They were educated to provide for themselves outside the city, and aborted at the age of twelve unless reprieved by a convenient death. The fact that most of them died within a few days was never faced.

  The failure to credit deaths to children not yet born was based on historical argument; at first, when this had been done, a black market in death records had been developed which had actually increased the city’s population and endangered the air supply — there was just so much sunlight per year available to the indoor plants, and there was seldom any success in growing photosynthetic organisms outside and transporting the oxygen indoors. The net result was that in about two thousand years the Blue Hill population had shrunk to about a quarter of its original twelve thousand.

  Kahvi’s bitterness had not decreased. She had had friends both younger and older who had been Nomadded both during her time in the school and after she had become a citizen. She had never been able to forget them. After her reprieve she had often gone outside with the hope of meeting one of them among the Nomads who occasionally passed; she had neither seen nor heard of them.

  Shortly after her sixteenth birthday, however, she had come across human remains in one of the “jails” scattered around the area to give recently aborted youths a chance for life and serve as living quarters for citizens doing necessary work outdoors. The fragments had not been recognizable as any particular individual, but she had never really gotten over the shock. Also, she had not been at all tactful in her remarks about the system for the next few months, and by the time she was seventeen had won the distinction of being the first adult in over five decades to be Nomadded.

  She had lived for several months in various jails, improving her survival skills, and then met Earrin with his raft.

  The man had been aborted at the normal age from Beehive on the Maine coast, a hundred and fifty kilometers or so north of the Boston area. He had been picked up at once by a long-established Nomad who had taught him the raft life. The older man had already been in his thirties, and had died when Earrin was about fifteen.

  Kahvi had taken to the raft to get farther from Blue Hill and its people. Affection for and from Earrin had come later. Their occasional return to the Boston area had always aroused memories, but she had learned to keep them far enough from her active thoughts so that they didn’t bother her — much.

  Her upbringing had of course made her self-conscious at first about her pregnancies, even though only Danna had survived. Now, however, self-confidence and self-respect had overcome this feeling, and she was now close to the point where she might have bragged about her family to one of her former fellow citizens. This time, common sense had submerged that urge; if the Hillers found out about Danna, some of them at least would feel it their duty to take the child for Surplus education — as a favor to the little one, of course.

  Kahvi’s mind wandered back toward the present. Invaders? Dangerous? Following Earrin?

  Obviously some Hiller had seen Bones, very probably the oxygen junkie in the jail had fled to the fire site; the people who had met Earrin could have come from there. Bones, however, had certainly never done anything to worry the citizens of Blue Hill. Were there other natives around? If so, what could they have done? Kahvi couldn’t believe that one of them would actually harm a person — at least, she didn’t want to believe it; she had left Danna in Bones’ care too often in the last five years. Natives ate plants, since there was nothing else for them to eat. They didn’t breathe, but as long as they got an appropriate mixture of nitrates and reducers they were all right. Their main drive was curiosity, if Bones were typical.

  Maybe one of them, or more than one, had tried to get into the city to satisfy that urge; but why should that bother the Hillers? The creatures didn’t breathe, so none of their precious air would be lost.

  And what had started this crazy notion that the natives had changed the world from a place wherepeople could live outdoors to what it was now?

  Kahvi had heard various versions of the legend that Earth had once been habitable for people, but had never really believed any of them even in school. There were lots of books, of course, which told of people being outdoors without any mention of breathing equipment, but some things were simply taken for granted, and of course the art of story telling must be nearly as old as humanity itself. Some things were too hard to believe, however entertaining they might be to hear or read.

  However, it was a fact that these Hillers seemed to regard natives as genuinely dangerous. This would have to be told to Bones when she came back; it seemed more serious than the mere unpopularity the native had experienced before. Was this what had been keeping Kahvi awake?

  Bones was a good and trusted friend; the idea of her being treated violently by anyone, and especially by Blue Hill citizens, was more than unpleasant.

  Danna stirred in her nest on the other side of the entry hatch, breathed more loudly for a few seconds, and was still again. The unborn child twitched slightly, and quieted. Kahvi remembered nothing more for several hours.

  Then the moon was shining on her, a waning gibbous disc high in the south. The comet was following it faithfully, four hours behind. Dawn could not be far away. Kahvi sat up and looked around.

  Sea and shore were brighter than by starlight, but still far from clear. There was no wind at all, and only a gentle smell moved the rafts and caused the reflections of moon and comet to undulate. Ashore, everything was still. No. There was motion. There were human figures by the pile of cargo, and some of the material had certainly been moved. What was going on? Could the Hillers be taking the material in the hope of not paying? That was hard to believe, but at least one of them was an oxygen waster, and that was equally incredible.

  Or was one of the figures Earrin? She could not be sure, even unmasked, that all the figures were human, though of course none was as tall as Bones. No, they were people — ordinary people, that is. But what were they doing? Making something from the cargo? Now they had stopped and seemed to be discussing something — they were all together in a group instead of spread over meters of beach.

  Now they were all moving away, toward the jail. There were five of them, and they moved slowly, as though they were tired. Kahvi watched as they approached the building and, one by one, disappeared into the air lock, leaving the landscape motionless again except for the reflections on the water.

  Kahvi did not have Bones’ insatiable thirst for information, but she was a human being with normal human curiosity. Human beings, not being p
arthenogenic, do have other appetites, but curiosity is still a normal and healthy human emotion, especially in an environment where accurate understanding of what is going on usually means life against death. The hunger for knowledge and understanding, therefore, characterizes intelligent beings of any species until age and waning vitality bring the conviction that everything important is already known. Kahvi, at twenty-five, was elderly, but she had lost very little of her vitality. The Hillers might be sleeping — but they might be talking, especially in a straight-oxygen environment.

  Carefully, to avoid waking Danna, the woman donned outdoor gear and slid into the water.

  Guided by the moon, she was able to stay under water until almost ashore. Carefully she raised her head and looked around; there was nothing moving, near the jail or anywhere else. She stood up and waded ashore as quietly as possible, and once out of the water ran quickly to the building.

  The air lock was toward her, with the moon shining on its surface, and she watched for ripples which would warn of someone entering it from inside.

  Then she ducked quickly around the northern end and into shadow. She paused briefly to catch her breath. Then she climbed the rough stone of the wall as Earrin had done, carefully raised her head above roof level, and looked through the transparent tissue.

  VII

  Captured, Conditionally

  “Bait.” The word was strange to Earrin. His Surplus schooling had included very little about the time before the change, and most of that was admittedly legend. He had never seen a fish or any other nonhuman animal native to Earth, and knew nothing of hunting or fishing or trapping.

  Even to the Hiller who had used the word it was shorn of nearly all its ancient implications except the central one. He did not try to explain it to Fyn.