“Invasion of the Pattern Snatchers” by David W. Goldman is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License . Human-readable summary: You are welcome to share this story with others, which includes making and giving away electronic or physical copies. But you must always include the name of the author, and you may not alter the text or title of the story. You may not charge a fee when sharing this story, nor use it for commercial purposes.

Originally published in Analog Science Fiction and Fact, September 2008

Invasion of the Pattern Snatchers

When he regained consciousness, Surgeon-at-Arms Roald Vik of the 3rd Armored Biomedical Brigade, Affiliated Planets Unified Defense Force, was only moderately worried by his initial view of the room. Unadorned pale-blue ceiling and walls. Institutional, glossy-surfaced armchair. On the wall opposite his bed, a curtain that he assumed covered an observation window. So: a typical jail cell.

But then he noticed the faint stinging scent, like rubbing alcohol—and his bed’s railing bore an impressive control panel. Frowning, he sat up and looked over his shoulder. Though he didn’t recognize the particular connectors on the wall behind him, in his brief career he’d seen enough monitor and life-support fittings to recognize the overall configuration.

But what sort of hospital bed lacked restraining straps?

Vik’s apprehension increased further when he discovered an excruciatingly tender, fist-sized swelling above his right ear. Had he crash-landed?

“Ah, you’re awake,” said a woman’s voice from somewhere near the curtained window. Vik couldn’t see a loudspeaker. But though he still had no idea why he was in a hospital, now the knowledge of his location and mission flooded back to him—for the woman had spoken in Flemish.

A bit over two centuries ago, an Affiliated Planets automated probe had discovered the world of Nieuw Vlaanderen orbiting a star about fifteen light-years from Vik’s homeworld, Eiriksson. Like all human colonies, Nieuw Vlaanderen was still recovering from the Collapse; like most in this region, its recovery had lagged Eiriksson’s by several generations. By the time of its discovery the planet’s leading civilization had regained a technology level averaging late-18th century Europe—well behind that period in physics and engineering, though significantly ahead in chemistry and biology.

As usual in such cases, after the probe’s initial reports had been received and reviewed, a message was sent instructing the probe to release a stealth depopulating agent into the planet’s biosphere. The A.P. in its patient conquests sought resources and territory, not opponents; no truly civilized society, surely, would prefer the untidiness and sufferings of war.

But in the century following the agent’s release, the probe failed to detect any drop in the local birth-rate. This unprecedented development, so potentially threatening to the A.P.’s longstanding strategy for expansion and regional domination, demanded urgent on-site investigation. And so sub-lieutenant Roald Vik, recently commissioned UDF Surgeon-at-Arms, was crammed into a cold-sleep pod and fired off on a seventy-year voyage to Nieuw Vlaanderen.

He could remember waking in orbit, seven decades of hypno-lessons in the probe’s observations—plus copious Earth history of possible relevance, including four dialects of Flemish—still echoing in his head. He remembered reviewing update summaries from the old but still-functioning probe, which in the two hundred years since its original report had identified a number of anomalies that didn’t match any previously recorded patterns of post-industrial cultural or technological development.

He’d chosen his first site to investigate. There’d been no crash-landing—he recalled his on-target arrival during an overcast night when neither moon was up. After ensuring that his ship was well camouflaged, he’d walked out of the forest to the nearby village. He could even remember the sickly looking fern-like plant sitting on the bar beside him as he sipped a beer and struck up a conversation with the bartender.

But then—? Vik touched the swelling above his ear. Had he fallen? Been attacked?

“Would you mind,” asked the woman’s voice, “if I opened this curtain?”

“Alstublieft,” he replied. Please. He tried to mimic her accent.

Motorized, the curtain slid open to reveal a large pane of glass. In the dimly lit room beyond stood a pale, dark-haired, middle-aged woman in a pastel blouse and white coat.

She leaned toward the glass. “How are you feeling, Mr. Boeykens?”

So she’d seen the identification papers he’d been carrying. He wondered what she made of their vagueness.

“My head, how—?”

“You don’t recall? Ah, well that’s not surprising—I’m afraid you struck it against a table when you fell. According to our investigator, you tripped over the leg of a chair as you followed him out of the tavern.”

Vik frowned. “Investigator?”

Her eyebrows lifted. “From the provincial Department of Health. Exactly what do you remember?”

“I was drinking witbier…a man sat beside me…” He struggled unsuccessfully for a clearer image, then shook his head in frustration.

“Please, don’t worry. A bit of amnesia is quite common with head injuries.”

Yes, of course, he thought—but how frustrating! What if he had discovered the newcomer’s association with the health department, and managed to steer the discussion to an aborted infertility epidemic of nearly two centuries ago? Maybe this “investigator” had already given him the answers that the A.P. required!

“In any case,” the woman continued, “what we really need to learn are some facts about you. Your papers are quite incomplete—we don’t know where you’re from, how long you’ve been visiting our province, who may have come into contact with you…?”

Vik refocused his attention. He’d taken her for a local physician, but now he wondered. Slowly, he said, “I’m sorry, but I don’t understand…why all of these questions? And why are you standing in another room? I don’t even know your name.”

She pursed her lips. “My apologies. I am Dr. Steibs, head of Infectious Diseases for the Department of Health. And you, Mr. Boeykens, are quite the mystery.”

“I’m sorry, but—”

“You are in an isolation room. If that bartender hadn’t been so observant, I shudder to think how many more people you might have exposed. It’s urgent that we trace your movements since your arrival.”

“Exposed?” Alarmed, Vik pulled up the sleeves of his loose pajamas in search of rashes. He felt at his face, tried to listen to his own breathing for wheezes.

“Please, Mr. Boeykens, calm yourself! We’ve already started you on the appropriate antibiotic. You’ll be over the infection in a few days.”

Some local bug, then—he must have picked it up in the forest. “What sort of infection?”

“Besnoitia speecki.” She spoke the name with careful enunciation and then leaned away, as if she had just delivered news of great portent and now awaited his reaction.

Besnoitia. The genus didn’t sound completely unfamiliar. He rummaged through his memories of General Microbiology…Some sort of protozoan parasite? Not one that caused any human diseases, though, he was reasonably sure. And certainly not an organism that the UDF had ever weaponized.

“I’m sorry,” he said. “But I’m not familiar with that—” he caught himself before using any terms that might reveal his medical training—“that germ.”

His statement apparently surprised her. “Surely you must have taken some classes in biology and history? Where did you grow up, Mr. Boeykens?”

He was afraid to reply—having planned for a casual evening in a pub rather than an inquisition, Vik had prepared only the sketchiest of cover stories. Now he wished that basic spy-craft had been part of the standard medical curriculum.

But, he realized, Dr. Steibs had already provided him with a perfect evasion.

“Why, I grew up in—” Drawing on his training in interrogating patients, Vik did his best to mime Sudden Unexpected Uncertainty. “In—” He moved on to Mounting Confusion, followed by Increasing Concern. “I can’t—” And now: Apprehension…and then, Alarm! “I can’t remember!”

Dr. Steibs frowned. “Please, Mr. Boeykens, this is very important. Try to focus on just the past few days. Can you recall entering our province? Our town?”

He shook his head in what he hoped looked like Fearful Misery. “No. I don’t remember a thing. I was sitting at the bar, but before that…it’s all a blank!”

“I see.” She crossed her arms before her chest and clucked her tongue a few times, looking thoughtful.

Vik, whose grades in Neurology had not been among his highest, began to wonder whether he’d picked such a clever stratagem, after all. Outside of adventure stories, how common was global amnesia?

But finally Dr. Steibs said, “All right, please try to remain calm. I expect that your memory will return over the next day or two. Don’t push too hard; just let it come on its own.

“In the meantime,” she continued, “I’ve got a different sort of question for you. One moment…”

Relieved that she’d accepted his performance, Vik watched as Dr. Steibs pulled a stylus of some sort from her pocket, and turned to the side. She leaned over as if writing or drawing on a table. He could see her make a large circular movement, and then several smaller strokes. Then she pushed something aside and drew a series of straight lines and curves.

Dr. Steibs straightened up and briefly examined her work. Then she lifted a white page and pressed it against the window; it remained affixed when she removed her hand. She smoothed a second sheet onto the glass beside the first.

She looked over the pages at Vik. “Tell me what you see.”

The first sheet bore a large circle containing three irregular shapes. At a glance he recognized the three distinctive continents of Nieuw Vlaanderen.

“A map of the world,” he said, wondering what she was after.

She nodded. “Very good. And what else?”

He turned his attention toward the second page stuck to the glass. But then he remembered his still-unexplained infection.

“This Besnoitia—” he forced himself to stumble over the syllables—“you haven’t told me its symptoms. Is there anything I should be watching out for?”

She shook her head. But Vik thought that she looked pleased about something.

“Just take your medication with each meal, and everything will be fine.”

“But the symptoms—”

“I won’t be able to explain those to you for a couple of days.” Before he could respond, she added, “I look forward to speaking with you tomorrow, Mr. Boeykens.” She touched the wall beside the window, and the curtain glided shut.

* * *

Meals arrived through a slot below the window. On that evening’s dinner tray, and again at breakfast, was a small paper cup holding a pair of pink pills, each embossed with a tiny “KM.” Vik swallowed the dinner pills. But at breakfast he set the cup aside when he returned his tray to the slot.

As soon as Dr. Steibs opened the curtain, maybe an hour later, he held up one of the pills. “What are you giving me?”

She pursed her lips. “You really do need to take your medication on time, Mr. Boeykens.”

“Just tell me what it is.”

She sighed. “That is koningmycin. A very old, very reliable antibiotic. Though if you don’t know about Besnoitia, then I don’t suppose koningmycin is familiar, either.”

He studied the pink pill, no wiser than before.

“Please,” she said.

He looked up to see her pointing at the paper cup. He shrugged, and then fetched a glass of water from the lavatory. He swallowed the pills.

Dr. Steibs gave him the smallest of smiles. “So—how is your memory this morning? Anything coming back yet?”

She didn’t seem particularly perturbed when he shook his head. “Well,” she said, “then we’ll just have to accept another day of mystery.” Vik wondered at her newfound lack of urgency. “Otherwise, I trust you’re feeling well? No headaches, dizziness? Blurry vision? Good. Could you take another look at my artwork here, and tell me what you see?”

Baffled, he approached the window to view the two pages still stuck there. “This is Nieuw Vlaanderen,” he reported. The second sheet held some uninteresting cross-hatching. He looked back at the map, then to her. “I told you that yesterday. What is the point of this? Some sort of psychological test? Or are you just curious about my knowledge of geography?”

“I think,” she said, “that I’ll be able to answer your questions tomorrow. In the meantime, try to dredge up any memories you might happen to have regarding lancet flukes. Or Toxoplasma.”

The curtain closed before he could respond.

* * *

When the curtain reopened the next morning, Vik again had something to show Dr. Steibs. Holding up an empty juice glass from his breakfast tray, he demanded, “Are all of your isolation rooms infested?”

Dr. Steibs peered at the tumbler as he brought it to the window. He thought he saw her lips quirk into a fleeting smile.

“Where did you find that?” she asked.

“On my leg!” He pointed at the tiny insect lying motionless at the glass’s bottom. “Look how swollen its abdomen is—it was sucking my blood! Probably infected me with some horrible new germs.”

“No,” she said. “I don’t think it has.” She bent down to squint into the glass. “Dermanyssus speecki.” Her voice had softened, as if she were fascinated at the sight.

He glanced at the bug. Maybe half a centimeter across, its many legs and antennae crisscrossed each other to form a peculiar, asymmetric pattern. He’d been trying to puzzle out that pattern for the past hour, but couldn’t seem to keep himself focused on the task.

“Say,” he asked, “your koningmycin doesn’t have any cognitive side-effects, does it? I’ve been having trouble with my concentration.”

Dr. Steibs looked up to meet his gaze, but before she could answer he recalled her apparent familiarity with the blood-sucker in his juice glass. “So, this is a common bug around here?”

“It used to be.” This time she didn’t try to hide her smile. “Nobody’s seen one in two hundred years.”

He gaped at her in confusion. Then she held up a finger, and swung it downward to point at her two drawings.

Where yesterday he’d seen only a dull jumble of lines and curves, today he saw a peculiar, asymmetric pattern. Very slowly, he rotated his juice glass until the bug matched Dr. Steibs’s sketch.

Vik stepped back from the window until he bumped against the armchair. He let himself fall into it, still holding the tumbler and its cryptic occupant.

“This,” he said, “would be a good time for explanations.”

Apparently she had a chair on her side of the window, too; when she sat, Vik could see only her head and shoulders.

“Are you familiar,” she began, “with the lancet fluke?” At his blank expression, she continued. “A parasite of cattle, back on Earth—it’s described in one of the library data crystals we discovered ten years ago. The fluke larvae take over the nervous system of their carrier, a particular species of ant. Every evening they force the ant to leave its colony and climb to the top of a blade of grass; it hangs on until dawn, then returns home and leads a normal day. This cycle continues until eventually a cow happens along and eats the blade of grass, thus delivering the fluke to its definitive host.”

Vik had had instructors like this—you asked them a straightforward question and they responded with what seemed like a complete non sequitur. When you fell into their trap by pointing out their failure to answer your question, they pounced with their prepared rant on the inadequacy of students these days. Only then did they finally provide the missing information that connected their initial response to your original question.

Vik had learned to deal with such teachers by looking attentive, and waiting. He did that now.

After a few seconds, Dr. Steibs continued. “How about Toxoplasma? Normally, of course, mice and rats become extremely anxious and fearful when they smell a cat. But infect them with Toxoplasma and not only do they lose their fear, they actually find themselves attracted to cat odors. Rather inconvenient for the rodents, as you might imagine—but Toxoplasma can only reproduce within the gut of its definitive host, a cat.”

Vik looked nervously at his juice glass. “So this insect—”

“It’s a mite, actually.”

“—this mite, it’s the carrier for the Besnoitia parasite that infected me? And the Besnoitia makes the mite want to suck human blood?”

Dr. Steibs looked quite disappointed in him. “No, Mr. Boeykens. The mite is the parasite’s definitive host. You are the carrier.”

The tumbler slipped from his fingers. Vik watched anxiously as it rolled across his lap and fell to the floor. He leapt to his feet. The unbroken glass was rolling toward the dark space beneath the bed; just in time he bent over and grabbed it. Letting out a breath, Vik lifted the glass for another look at its occupant. The tumbler was empty.

Vik jumped backwards, banging an elbow on the wall. Then, frantic, he scanned the floor all around the chair. After several long seconds he finally saw the mite, near where the glass had initially landed. On its numerous legs it was advancing, very slowly, toward Vik’s bare foot.

He slammed the inverted juice glass to the floor, trapping the bug inside. Then, with great care, he slid the glass and its prisoner toward the middle of the room. Keeping his eye on the glass, he stepped backwards until he could once more lower himself into the armchair.

As Vik began to catch his breath, Dr. Steibs raised an eyebrow. “Shall I continue?”

“Alstublieft,” mumbled Vik.

“These mites, we assume, are ubiquitous wherever humans live. Although of course we can’t prove it from only Nieuw Vlaanderen observations, the degree of specialization evolved by both Besnoitia and the mite strongly suggest that they have been living with our species for thousands of years. Perhaps since before the earliest civilizations.”

“But—”

She held up her hand to head off any interruption. “The mite acquires Besnoitia from an infected human’s bloodstream. The parasite reproduces in the mite’s salivary glands; its larvae then escape into another human when the mite next feeds. From there the larvae travel to their carrier’s brain, where as they mature they exert an exceedingly subtle cognitive effect.”

Vik had regained enough composure to want to reassert his own cognitive abilities. “The human,” he hazarded, “loses the ability to see that pattern.” He pointed toward Dr. Steibs’s drawing.

“Nearly correct.” She tilted her head, apparently not completely unimpressed with him. “Infected humans can still see the mite; electrophysiological studies have confirmed this. But the sight becomes remarkably uninteresting. One glance dispels all awareness of the mite—including not only its image but also the tickle of its feet, the pinch of its bite. Anyone who discovers one of the mites immediately forgets that discovery.

“Koningmycin,” she continued, “was chanced upon quite accidentally. But once people could see the mite, it didn’t take long to also uncover the parasite and work out the details. We thought we had long ago eradicated both organisms worldwide—until you came along, Mr. Boeykens.”

Not wanting her to pursue that line of thought, but also genuinely curious, Vik asked, “Getting rid of the Besnoitia, what health effects has that had? Besides allowing people to notice the mite.”

Again her head tilted. “A very perceptive question. Indeed, there have been three beneficial effects. Five percent of schizophrenia cases had lacked a known cause—now it’s known, and eliminated. The same for half of all previously unexplained epilepsy.”

“Impressive.”

“But it’s the final effect that has had the greatest impact. What would you say is the defining aspect of life?”

The question took Vik off guard. But this was merely another familiar variant of instruction by non sequitur—how he answered the apparently irrelevant question wouldn’t actually matter. So he offered the first response that occurred to him. “Reproduction?”

She dismissed his reply with a wave of her hand. “No, Mr. Boeykens. Pattern matching.”

Vik was intrigued; none of his instructors had ever suggested such a connection.

“Consider: a rabbit detects a certain canine aroma, or hears a distinctive padded footfall; immediately it recognizes a pattern of danger, and flees. Just as the same rabbit will dig up the root of a plant whose leaves it has learned to associate with food. And that plant, too, is a pattern-matcher, responding to lengthening periods of daylight by developing flowers.”

“So,” Vik asked, “then computers are also ‘alive’?”

She snorted. “Computers are merely tools of human pattern matching. But it’s pattern matching that’s behind every intelligent, conscious human behavior, from language to music to science to interpersonal relationships.” She paused and looked at him expectantly.

“What’s this have to do with Besnoitia?”

As Dr. Steibs shook her head in apparent pity at his intellectual shortcomings, Vik cursed himself for falling into her pedagogic trap. She really was very good.

“The patterns recognized by humans,” she said, “are often exceedingly abstract. But anyone infected with Besnoitia loses the ability to work with an entire class of abstract patterns—those that share any significant features with the image of that mite. It’s as if they lived in a world of geometry problems but could never grasp the concept of angles.”

At Vik’s obvious confusion, she said, “I’ll give you an example. About thirty years after the discovery of koningmycin, a clerk in a provincial Vital Records department felt there was something odd in recent birth numbers.”

Vik tried to hide his surprise. Could Dr. Steibs be describing the A.P. probe’s attack? The timing would be about right.

“The clerk couldn’t point to any specific discrepancy, but when she visited the neighboring provinces and reviewed their records, again she felt there’d been a change from past trends. We had no computers then, of course, and statistics was still in its infancy. So it took her several weeks of poring over her records to pin down the strange pattern she had sensed.

“The clerk found a very slight increase in the ratio of female to male babies. But not all mothers were affected equally; those who had been the first-born of their siblings were spared.”

Vik swallowed. This was exactly the first-generation effect designed into the A.P.’s engineered bacterium, to help mask the initial assault. Of the few other attacked worlds that had identified this pattern, none had ever managed the feat before the bacteria’s secondary effects were already well established.

Dr. Steibs continued. “The clerk published her findings. Nearly simultaneously, so did four other clerks from four other countries. Still, it took a couple of years to isolate the bacteria responsible, an oddly mutated form of Wolbachia. Heard of it?”

Vik worked to keep his expression blank as he shook his head. He didn’t know how much of this incredible tale he should believe; not a single previous planet had even confirmed that a bacterium was the cause of their fertility problem—let alone isolated it.

“No? Well, Wolbachia normally infects invertebrates, so this was a bit of a surprise. Even more surprising, this particular strain—which proved remarkably challenging to grow in culture—was resistant to all the usual classes of antibiotics. In the end it was a bit of a race, coming up with a new antibiotic before the bacteria could spread widely enough for its other effect to matter.”

“Other effect?”

“Ah—should both parents carry the infection, all of their offspring would be female. I see you recognize the inevitable consequences.”

Vik’s expression of horror, though, reflected not sympathy for the aborted genocide Dr. Steibs described, but rather fear of what these people could one day do to his own.

Freed of humanity’s millennia-old parasitization by Besnoitia, apparently Dr. Steibs’s forebears had—in just a couple of years—not only detected, but correctly analyzed and then neutralized a weapon whose mere existence had eluded most of its previous targets, a weapon whose effects had never before proven less than catastrophically fatal. Once Nieuw Vlaanderen regained space travel, how long until its people threatened the Affiliated Planets? With such superior pattern matching abilities, how likely were they to lose any kind of interplanetary battle?

His superiors had been correct to send an investigator here!

But, Vik realized, he now held the power to even those future odds. Once he transmitted a description of Besnoitia and its mite back to Eiriksson—even better, what if he managed to carry home a sample of koningmycin for analysis?—then his own people could free themselves of the parasite, too. Who knew what insights and breakthroughs might follow? And what accolades for the humble soldier who’d brought his people such knowledge?

He was picturing himself at the christening ceremony for a battlecruiser bearing his name, when he realized that Dr. Steibs had risen from her chair.

“Now that you can see the mites, you can assist in your treatment. After feeding, the mite disengages for 48 hours, until its next blood-meal. You’ll find them lying in your bed-sheets, or hiding in corners. Kill them as you discover them.”

“And then I can leave this room?”

She smiled. “72 hours after the last sighting, yes. Though you’ll still need to complete a full two weeks of the koningmycin to guarantee the eradication of your Besnoitia.”

Even as the curtain slid closed, Vik approached the inverted juice glass on the floor. He bent over and lifted the glass, leaving its inhabitant behind. Then he returned the glass to the floor right-side-up—with, as his Therapeutic Pathology instructor had been fond of saying, extreme prejudice.

* * *

Vik’s clothing, fumigated and laundered, had preceded his breakfast through the delivery slot this morning. While the maroon turtleneck sweater, black denim trousers, and lightweight boots were barely familiar to him—he’d chosen the ensemble from his ship’s extensive wardrobe, and worn it for less than a day—he found their weight and varied fabrics reassuring after a week of flimsy hospital pajamas.

When Dr. Steibs opened the curtain he told her, “I’m going to miss our little chats.”

She granted him a slight smile. “I’m sure that you’ll find your doctor in the rehabilitation clinic at least as entertaining. Or have you recovered your memory since yesterday?”

Vik hurried to don an expression of Deep Concern. “No, nothing at all.”

“The Hollebeke clinic has a very good reputation; they’ve managed tougher cases than yours. Still…”

“What?”

“The train to Hollebeke doesn’t come through until late this afternoon. You might want to spend the next few hours wandering around town. See if you can stir up any recollections before you leave.”

Vik nodded. “We’re done, then?” He stood.

“Apart from some paperwork, yes.” She wagged a finger at him. “And you must finish all of your antibiotics.”

He patted the trouser pocket that held his bottle of pills. “Don’t worry. I’m not going to lose these.”

Vik turned toward the room’s locked door.

“One last thing,” said Dr. Steibs.

He turned back. She pointed to her drawings.

He had to laugh. “Believe me, Dr. Steibs—after three days of hunting and squashing mites, I’m never going to forget that pattern!”

She smiled politely. “Humor me.”

With a sigh, Vik glanced at the drawings, then back to her. “Still the same pattern. Really.”

She reached toward the wall beside her window, pressed some control there. Vik heard a click from the door’s lock. As he turned again toward that door, Dr. Steibs said, “Good luck, Mr. Boeykens.”

One day, Vik thought, Dr. Steibs’s descendants were going to wish that his luck had been a good deal worse.

* * *

“All right. No, don’t follow him any further. Yes, okay. Good.” Steibs hung up the phone. She clucked her tongue as she stared out her office window.

After strolling apparently aimlessly through the village for over an hour, Boeykens had abruptly headed straight for the pub where he’d originally been picked up. But he spent only a few seconds loitering outside that pub before turning and marching into the nearby woods.

The woods where last week they’d found his spaceship.

Until the ship had been discovered, Steibs hadn’t been as convinced as her colleagues of her patient’s otherworldly origin. But after that discovery—not to mention the analysis of his genetics—she’d relinquished any doubts.

Steibs sighed. No one could be sure that “Boeykens” came from the same world that had sent the infertility plague. While his DNA did bear many of the same engineering residues as that of the modified Wolbachia, this was at best circumstantial evidence—some other world might have happened to employ the same splicing enzymes. She’d hoped to get a rise out of him when she’d related the story of the discovery and analysis of the Wolbachia plague; if he’d been surprised by her tale, though, he had covered his reaction immediately. He really was very good.

Steibs turned back to her computer, where her unfinished report waited.

They’d been fortunate that the bartender had recognized the mite crawling along his counter, and that he’d so promptly called the health department. She’d already written a commendation for her assistant’s quick thinking in knocking out Boeykens and hauling him to the hospital. Even so, two dozen people had needed prophylactic koningmycin, and the bar had to be closed for intensive fumigation.

Wherever he came from, Boeykens would presumably soon be flying home to share the discovery of koningmycin with his people. In that, at least, she could take some professional pride—she was a public health officer, after all.

Steibs lifted her two drawings from the desk. She winced at the clumsiness of their execution; still, she felt that she’d captured the mite pattern rather nicely.

She had not enjoyed the heated arguments over teaching Boeykens about Besnoitia and the mite. The military had been against treating him at all, not to mention educating him and handing over samples of koningmycin. In the end, though, it was her colleagues’ plan—conceived, engineered, and put into a freezer half a century ago, against the possibility of someday receiving just such a visitor as Boeykens—that had carried the day.

Yes, Boeykens’s people would rid themselves of Besnoitia. And yes, they would therefore gain pattern matching skills to rival those of Nieuw Vlaanderen. But those skills would never be used to attack her world.

Twice a year, for the rest of his life, Boeykens was going to develop a mild respiratory infection. His sneezes were going to expose his colleagues to a very special pair of viruses, both of which should spread quite widely in just a few seasons—unimpaired by koningmycin or any other antibiotic. Then, once a given populace developed a high enough prevalence of the viruses, a very specific side effect would kick in.

As a test, Boeykens’s isolation room had been sprayed not only with the two viruses but also with an aerosol mimicking the virus-induced pheromones of an infected population. The side effect had worked perfectly, leaving Steibs confident that her descendants would never meet anyone from Boeykens’s world—unless it were her descendants who took the initiative.

She looked again at her drawings. The image of a mite that humanity hadn’t noticed for millennia. And the image of her own planet.

An image that Boeykens hadn’t noticed for days.