When the first drinking glass hit the floor and broke, Private Grace pressed her back against the wall and steadied the sidearm with both hands. The window above her was single-paned, the weatherstripping rotten. To her left, a freestanding radiator was rusting gently. The house was a summer cabin, cramped, and redolent with the smell of mice. They'd spent the better part of an hour nailing the windows shut, then gathering glassware—pitchers, vases, dinner plates, a souvenir ashtray with a cartoon walrus painted in the bottom—and arranging the dishes in rows along the sills.

Now, they hunkered down, waiting. There had been food at least, canned, coated in dust. They ate quickly, passing the open cans back and forth as evening fell. The sound the glass made when it landed was explosive, a mortar going off.

"What do we show these giddy bastards?" Whitaker called from the adjoining room, sounding clipped and perfunctory.

The answer came from a dozen positions, followed by the metallic sound of carbines, magazines and bolt assemblies clattering into place. "No mercy, sir."

They had begun as an infantry platoon of forty-seven, mostly up from New Mexico and Texas. Now, they were thirteen. Ten privates, one combat medic, and Denton the Marine, all serving under Whitaker.

Of the privates, only Grace and a trooper named Knotts were from Whitaker's original squad. The other eight and Jacobs, the medic, had come off a company that had gotten pinned down at the Air Force base and, for the most part, died there.

The base had been a short-term El Dorado, but when they arrived, their grand welcome was absent, save for a few survivors holed up in the bunkers. Some of the medical technicians had made a last-ditch effort to seal themselves in the sleep chambers. It was difficult to say whether the massacre had happened with the techs scrambling for safety or already in stasis, but one thing was certain. The flyboys had been dead for weeks.

Where Denton originated from remained somewhat of a mystery. It was theorized that he was a deserter, but in truth, Grace did not much care. Denton had the best guns.

"Smirkers," someone shouted in the front hall, immediately followed by a crash as the door splintered. Fire came in three-round bursts, rattling through the tiny house.

Grace crouched lower, sinking into her nanovest, bracing her shoulder against the radiator. She checked the cuffs of her jacket, tucked them deep into the tops of her gloves. Outside, pale hands seemed to float, palms flat against the windows. They were laughing, a storm of high-pitched giggles.

They smiled. No training in the world prepared you for that. They smiled as they slashed and bit, tearing flesh off their victims in chunks. They smiled as they ran, a merciless full-out sprint, headlong, ravenous. They smiled right before you leveled the barrel and squeezed the trigger. Sometimes, if the shot was high enough, the caliber small enough, even when they fell back—smoke rising from a neat round hole in the forehead—they were still smiling.

Jacobs said it was neurological, an involuntary tic. He talked about them a lot, his language precise, his hands sketching neural pathways. It had been his idea to come up here, strike for the research complex near Rosewood. They were close now, a couple miles off, but the slopes were crawling with smirkers and everything had started to seem wildly impossible.

A window broke somewhere and the house was suddenly awash with a new influx. They poured into the little common room. One was wearing a Christmas sweater, red, sprinkled intermittently with green trees, white reindeer.

Against the other wall, Denton was cutting swaths through the mob—systematic, businesslike. His arms were massive, the muscles displayed in sharp relief as he swung the carbine up. The smirker in the Christmas sweater was closing. It moved fast, turning on him with hands outstretched.

"Semper Fi," Denton said, but it sounded flat and ironic. He jammed the muzzle in the smirker's face.

In the front hall, Private Sutter was shouting something. He was always shouting, hooting, whooping. Sutter, with the God-awful tattoo on his neck, upwards arrow pointing to the base of his skull. Corsican script said, in an incongruously graceful hand, Eat Me.

Smirkers did not, in actuality, express much preference for the brain over other organs. They seemed content to take any piece they could get, but the celluloid lore of old movies was hard to shake.

In the last few weeks, some of the Privates had taken to painting targets on their helmets. Aim here in case of infection. Whitaker didn't like it, but allowed the targets in the same indulgent way he allowed Sutter's tattoo. Harmless, letting off steam. Grace thought it was morbid.

The window above her fell in with a glittering crash, and she rose and popped the first smirker in the face. It slumped forward and she turned to meet the two that came after, dropping them on the carpet. After that, the process became automatic. Her territory extended outward for two yards and ran the distance of the wall. Every other inch of the house was someone else's problem.

Something moved behind her and she swung around, already reaching for her combat knife. It had been a boy, sixteen, maybe seventeen. The face still bore the faint interruptions of acne. He grinned and his teeth were coated in a thin veneer of blood.

The carbines were light, easy to maneuver, and the sidearm was more versatile still, but for such close quarters, Grace favored the knife. She slipped it from the sheath and brought the blade up. The throat first, and directly after that, the right eye.

Preferred it controlled, preferred it close. Some of the others couldn't stand to let the smirkers get near. Instead, they ran themselves out, not keeping count. A dull, shocked look when the handgun clicked empty. They thought about themselves before they thought about the job. That was the secret; if you thought about the job before you thought about anything else, if you just did your job, you got out. She drew her hand back, let the boy drop, and stepped over him. She wiped the blade on her fatigues and then peeled the gloves off. They were soaked.

The shooting had stopped. Grace stood, contemplating the room. Her heart beat hard and fast in her ears, and she could not precisely reckon how much time had passed. Smirkers lay everywhere, sprawled out, tangled together on the floor. After a cursory check to make sure that none were still moving, she started for the doorway.

In the front hall, she found Emery, standing with his back to her. His rifle hung at his side and he was breathing in long, whining gasps.

He was one of the ones with a target, a concentric bull's-eye painted in red on the front of his helmet. But when he turned toward her with a mystified expression, the bite on his shoulder already weeping yellow, she aimed for the eye socket. He whimpered and begged a little, but in her head, she had squeezed the trigger a thousand times, and it was no great effort to do it now, in the cramped cabin, with the daylight dropping away and the smell of bodies heavy in the air. The report was very loud in the narrow hall. At her feet, he lay still. After a moment, the blood began to pool out from under him.

Her progress through the house was slow. The floor was littered with debris, spent ammunition. Bodies lay with their limbs jutting at odd angles—smirkers and soldiers. They were mostly accounted for. She didn't recognize Denton at first, except by his size. Someone had shot him in the face. There were bite marks all over his arms. His skin oozed with the thick, pestilential yellow of infection.

In the kitchen, she found Sergeant Whitaker. He was propped in a corner, shoulders wedged in the join between two cabinets.

He looked up at her—a hard, dignified look that stopped her in the doorway. The side of his neck had been torn away, leaving shreds of muscle, exposed tendons. His voice was hoarse and liquid. "Are they dead?"

She did not know if he was referring to their makeshift squad or to the recent barrage of smirkers. "Yes, sir."

"What do you think those Washington fucks are doing right now?"

Dead, of course, all dead. Except the ones still shambling around smiling to themselves. Giggling their high-pitched giggles.

"They don't pay me to think, sir."

Whitaker laughed at that, a wet, clotted sound. "No one's paid us to do a damn thing in months. Maybe you could take up thinking as a sideline. It wouldn't have to be on the clock."

He laughed again, viscous, close to choking. The stripes on his sleeve were the brightest thing in the room. The gold looked almost white in the failing light. The blood was seeping out of him, leaving his face gray. Infection imminent.

"You should've made Corporal," he said, and it sounded watery. "I'm sorry for that."

"Don't worry yourself, sir. I don't imagine I would have cared for it."

"You never know. Look at you now—you're the one who's going to walk out of here tonight."

Blood and foul yellow seepage were running down the side of his throat, soaking into his shirt.

"Do you want me to take care of it?" she said, jerking her head in the direction of his sidearm.

He smiled at her, a slow, complicated smile. "No, I got this."

She did not disbelieve Whitaker, even at the last. He was a good man, dependable. Already holding the 9mm to his temple. But she stood in the doorway to make sure. The report made her flinch. When he slumped forward and his hand let go, she turned and started back through the house.

A wooden pull-down ladder stood spindly and erect in the hall. It was fixed to the ceiling by a hinge, and led up to an open skylight. The angle of the ladder was stark, surprising. In the past weeks, the world had taken on an increasingly surreal cast and the ladder did not seem disconcerting now, but only natural and right.

"I'm coming up," Grace said, to no one in particular—to whomever might be at the top, waiting to put a bullet in the first person to stick their head through the opening.

On the roof, Jacobs the medic was sitting with his legs drawn up and his elbows resting on his knees.

"How do they always know?" he said, staring off over the hillside, the dark trees. The sky was deep purple, already speckled with stars. "We go along, covering our tracks, moving in the daytime. And still, they always know."

Grace nodded, because his assessment was true. Not a thing you argued with, but how it was. They would always find you. It was what they did.

"There aren't any bugs up here," Jacobs said.

"No," said Grace, taking a pack of cigarettes from her pocket. "No, I haven't seen any."

"It's the air. It's thin."

She wondered if he was cracking up. He didn't seem the type, but still, with these smart ones, it was hard to say. Sometimes they fell apart, just from thinking too much.

"They're not hunting people," he said.

"What do you call it then—what they're doing?"

"I mean, they're not hunting people exclusively. They're not strictly cannibals. We saw eviscerated deer when we were coming up—and rabbits—but they're not picked clean. They never eat the dead."

Grace pulled a cigarette out of the pack with her teeth, lit it. Her hands were steady, but felt light and disconnected.

When she breathed out, Jacobs coughed and fanned at the air. "How does something like this just happen?"

Grace observed Jacobs, his raised head, his profile, hard against the velvety sky. She assumed he must be talking in some broad, abstract sense, because the how-and-why of it was far from mysterious.

The methodology was simple. Escalating reports of a blood-borne pathogen carried by insects, high fatality rate, drug-resistant. The government had been frightened of pandemic. They had pushed immunization, pushed it hard, and in the end, they got their pandemic, all right. A vector that began at vaccination and exploded outward, extravagant. Uncontainable.

It had begun on the West Coast, vaccination facilities popping up in grocery stores and shopping centers. And everyone lined up. It had taken approximately six hours to ascertain that something was wrong, but in that time, the event had affected nearly half a million people. And it spread like fire. In a way, it was good the infection came on fast. Otherwise, they might have all had the shot, every last one of them, offering their arms to the needle without the slightest indication that anything was amiss.

"What if it's a signature," Jacobs said, turning to her.

"I don't follow."

"A carbon dioxide signature. Blood-seekers—they know to come after you. They follow a trail of chemicals, a stamp. Mosquitoes can sense living blood from almost forty meters."

Grace nodded as he spoke, not comprehending his train of thought exactly, but not needing to. The words sounded round, fat, reassuring.

"We could verify it," he said. "All we'd need is a controlled environment, some preliminary tests. We could keep going, get to Rosewood. They'll have everything we need. It would only take a few trials. I mean, then we'd know. And Rosewood's only four miles out. If we run—"

"If there's any still in the woods, they'll be on us in two seconds, sir. I don't see much chance."

Jacobs stood up, brushing impatiently at his fatigues. "There's a way, though. There's always a way."

He started down the ladder, his boots clattering on the wooden rungs. There was a smear of blood on the back of his shirt. Grace squashed the cigarette under her toe and wondered again if they were only prolonging something inevitable.

It didn't matter. With a purpose, a mission, the blackness of recent days did not seem so close. They would go to Rosewood and test his theory. Jacobs was not Whitaker, but he was capable. He knew things. And a short-term itinerary was better than none at all. They would go to Rosewood and find a brilliant solution. After a minute, Grace rose and followed Jacobs down.

In the bathroom, she found him standing over the body of Knotts, legs splayed to avoid the mess. He had opened the medicine cabinet and was rummaging along the shelves.

"What are you after?"

"DEET," he said, flinging bottles and tubes from cabinet haphazardly. "Why don't these rednecks have any fucking DEET?"

"You said it before, sir. There's no bugs up here."

The floor at his feet was littered with adhesive bandages, aspirin, a topical antibiotic.

"Knotts was up from Florida," she said.

Jacobs gave her a distracted look, then turned back to the cabinet.

"They got bugs in Florida like you wouldn't believe. I bet he carries it in with his personal effects. A thing like that, it just gets to be a habit."

"Check him then, check his things if you think he's got it." Another bottle hit the floor. The cap flew off and a cascade of white pills rattled across the linoleum, washed up against the motionless form of Knotts, got stuck in the congealing blood.

"And you think we could keep them off us? With mosquito repellent, sir?"

"It doesn't repel, it interferes. It corrupts receptors."

The logic was mysterious. Grace was not much in the way of parsing scientific theories, but he seemed to be missing a vital link, some key component. A person is not a mosquito, she thought of saying, but in the end, she knelt over Knotts' body and began to pick through his satchel. The bottle of bug spray was very small.

"Give it to me," Jacobs said, peeling his shirt over his head.

"Is this enough?"

"It'll have to be, won't it? It doesn't last more than an hour, hour and a half, anyway. We just need to get beyond them." He was already smearing the stuff down his arms. "Take off your vest."

"I'm sorry, sir?"

"Take it off. And your shirt. We need it thick, all over. Put it in your hair."

"What if it doesn't work?"

"Does it matter, then? We're dead anyway. Everyone's dead eventually."

And that was logic she couldn't argue with.

They reached the Rosewood complex shortly after midnight. The moon was pale and heavy in the sky, fat as a dogtick. Their progress went undetected, although Grace had no position as to whether it was due at all to the DEET.

They crossed the perimeter of the complex. The west entrance already stood open, a dark gaping maw. Jacobs lit his xenon lamp, holding it to the doorway. Somewhere beyond the halo of light, a shape was moving.

Grace loosened her gun in its holster. "Something's there."

"Good," Jacobs said. "We just need one. I want one alone in the lab for fifteen minutes."

Grace nodded and didn't answer. There was never just one.

From far away, a shrill giggle rose. It echoed back and forth in the corridor, trickling down the walls. Another came from somewhere in the northern sector.

At the reception station, they paused to examine the attendant signs of disuse. The control panel was coated in dust.

Jacobs indicated a bank of monitors. "See if you can bring the lights up while I find the medical bay. I need to get some supplies together."

Grace nodded again. Her skin was prickling with adrenaline, but this was not the time to go jumpy. There would be warning. There always was.

When she accessed the backup system, the lights came up sluggishly on the generator, hazy and dim, like being underwater.

She stood in the reception area and waited. The time that passed was deep and faceless and full of sound.

When an unwieldy figure came toward her down the hall, she raised her pistol, but it was only Jacobs. He wore a biohazard suit, fitted with a portable respirator and a curved Plexiglas face-mask. With one gloved hand, he gestured her to follow.

He led her through a maze of corridors to the medical wing and ushered her into a glass-fronted observation room. Grace maneuvered between counter tops and stasis chambers to peer through the long window into an adjacent exam room.

The girl was in bad shape, skin discolored, covered in welts and scratches. She was smiling the smile, gleeful, manic. Grace watched her make a circuit of the room. Eight or nine years old. Must have belonged to one of the technicians, maybe a project manager. The girl had been someone's daughter.

Jacobs turned from a cooler at the far end of the room. Cupped in his hands was a white rat.

"Is it dead?" Grace asked.

Jacobs shook his head. He had to spit out the mouthpiece before speaking. "They've got hundreds in there, in stasis. I'd say we've got five, maybe ten minutes before it comes up. I need to see what she does."

Grace touched the rat's side. Its fur felt cold and matted.

Jacobs secured the face-mask again, then motioned her away from the exam room door and entered, carrying the rat.

The girl reacted with no particular venom to Jacob's presence.

When he offered his gloved hand, she took it without looking up. He lifted her and set her on the edge of a gurney. He left the rat resting beside her.

Back in the observation room, he took off the headpiece and set it on the counter.

"Now watch," he said, leaning towards the glass.

The girl sat where he'd left her, swinging her feet, smiling the deranged smile. Beside her, the rat lay peaceful and motionless.

"Right now, its body's still retaining carbon dioxide, but as it comes up, the emissions will be transiently high. It's going to be a little CO2 bomb in a minute."

The rat twitched violently.

When the girl moved, it was with unexpected ferocity, snatching up the rat and sinking her teeth into its side. Blood ran copiously, soaking into the front of her dress.

As Grace watched through the glass, the girl's eyes turned up to meet her gaze. She was holding the animal to her mouth with both hands and then she let it fall. Blood was dripping from her chin and the rat lay motionless and red on the cement floor.

Jacobs had pillaged a battery-powered tablet from somewhere and was making rapid marks with the stylus, murmuring to himself.

There was a low, industrial whirring as the fans came on. Grace flinched as the ventilation system roared to life. Jacobs only stood with his head bent, tapping at the little screen.

On the other side of the glass, the girl began to pace frantically, scraping at the walls with her fingers.

"What's she doing?"

Jacobs glanced up. Above them, ducts ran along the ceiling, their shining planes punctuated by vents.

"She's just got a whiff of us," he said. "The air's circulating again."

In the other room, the girl was scrabbling at the floor vents and then at the edges of a broad grate in the wall. It occurred to Grace that if the DEET worked like Jacobs said it did, then the girl wasn't responding to it. That she must be smelling something else. Or maybe the DEET didn't work after all, but was only a placebo. She did not know whether Jacobs had intended the fallacy to comfort her or himself.

"Are they really mindless?" she said, with her palms against the glass.

Jacobs looked at her strangely. "You mean, did they experience brain injury? If we could mitigate the reaction to incidental levels of CO2, we'd be certain. But no, I don't think they're stupid."

The lights failed then, and the room lapsed into blackness except for the flicker of the tablet. Without ceremony, Jacobs lit the xenon lamp and continued his notations. Grace reached for her sidearm.

Out in the corridor, footsteps echoed. Multiple people—eight, nine maybe—and coming closer, but they were unattended by the manic sounds of laughter. Grace moved so that her back was to the wall.

Jacobs still scribbled on his tablet, letters slanting down in a frantic scrawl before the CPU converted them to type. He was talking to himself under his breath, alive suddenly, animated. His intensity had become frantic, bordering on possession, and it frightened her.

The door swung open and the strangers came in slowly, with wary looks and raised guns.

"Who are you?" said a tall, craggy man at the head of the group. He stepped into the light. "What are you doing here?"

He wore no uniform. Someone had sewn stripes onto the sleeves of his jacket, but the stitches were sloppy, inexpert. A scar ran across the bridge of his nose and then jagged abruptly down one cheek. Behind him, a contingent of men held firearms. Mostly hunting rifles and shotguns.

Grace moved forward, standing at attention. "Private Maureen Grace and Sergeant Rabe Jacobs, 68W."

The man nodded. "Trask," he said.

He gave no rank and did not need to. His manner conveyed the brutal authority of a general, although the unit behind him was motley. Probably local militia. He was looking past her to the bare desk and the glassed-in examination room. "And what are you doing here, Private Maureen Grace?"

She glanced at Jacobs, who sat limply, watching the newcomers with the air of someone drugged. "We're investigating a possible course of action. The Sergeant's developing a theory and has acquired a research subject."

"This research subject here?" Trask said, raising his pistol to the glass. "This raggedy little bitch right here?"

At the desk, Jacobs set the tablet down. "What are you doing? She's not a threat, you moron. She's just a little girl."

The look Trask gave him was long, calculating. "And she'd have your throat out in two seconds."

"I had her calm. I had her sedate, even when I was in the room. We have all the preliminary evidence necessary to pursue this. Are you listening? We could alleviate their aggression. We could fix them!"

"And lead them around like pets? Keep them until they've had enough one night, and kill us in our beds?"

Jacobs scrambled up from the desk. "It is our duty to cure them."

"There is no cure," Trask said, coming down hard on each word. "No cure but to rout them, and pick them off one at a time until it's over. There's no way to play nice and then go home."

Around him, the other men nodded, their gestures tied to his orbit like moons or planets. Grace watched them. Trask embodied all the qualities vital in a leader. His voice was low and commanding. His face was honest. It promised suffering to anyone who got in his way.

Above them, the ductwork clattered. In the eerie glow of Jacobs's lantern, the men started, raising their weapons to the ceiling.

Grace crossed to the observation window and pressed her face to the glass. "She's gone, sir."

When the ventilation duct dropped down into the observation room, the sound was very loud. The whole apparatus seemed to peel away from the ceiling—a long, shining arc that hung for an instant at its apex, then crashed to the floor with a deafening clang.

Grace watched as a dim figure scrambled out on hands and knees, slashing and clawing at everything in reach. Lank, dirty hair, tattered dress, dark splatters down the front. Then nothing but the smile. The handgun was light, not powerful, but efficient, up out of the holster and in her hand. She put the girl down from eight yards.

Beside the desk, Jacobs lay under the remains of the duct. The aluminum had torn jaggedly, like a mouthful of teeth. Her ears still rung with the sound of metal striking cement and on another plane, laid over the metallic clatter, the shot echoed again and again.

She did not recall crossing the room, but there she was beside him. His cheek had been raked open and he gasped for breath, looking up at her. A dull, shocked look, like he was offended by the treachery of the world. The wound in his side was long. Not a puncture, but a ragged gash, first through the material of the biohazard suit and then through his skin and after that, the subcutaneous fat. The blood was bright, arterial red.

Grace knelt over him and pressed her hands to the wound.

Somewhere in the ducts, a sharp, high-pitched giggle broke loose, echoing down on them like spilled nails.

"Welcome to the zoo," Trask said behind her.

"You know I'm right," Jacobs whispered. "Don't you know I'm right?"

But Grace knew nothing about chemistry or pathology. The mysteries of science were Jacobs's domain, and the brilliance of his vision eluded her.

He was coughing now, bloody saliva collecting at the corners of his mouth. On the other side of an examination table, the dead girl grinned and grinned.

Trask moved closer. He was wearing work-boots and the soles squeaked on the linoleum. "Look at his face. He's infected anyway. You know it, I know it. Just end it—for him and for us. We need to be strong if we're going to restore the nation."

All through the compound came the sounds of scrabbling, shuffling laughing. Grace had a strange, unbidden thought. There is no nation; only people.

Under her palms, Jacobs coughed again. The skin around his eyes had taken on a bluish hue.

Trask had nothing on his side but grim conviction and force of will. A man who was simply not afraid could persuade the masses to follow him anywhere. He might not be a war hero, but he could marshal the survivors.

Above them, the metallic clamor was much louder. Grace lifted her hands.

She raised the gun, held the muzzle to Jacobs's cheek. His eyes were pained and cloudy. She felt for the trigger and did not think, because it was easier not to.