“Here’s the deal. We don’t get to cross this perimeter.” A blue line, crudely sketched in chalk, ran across the polished floor. It looked to Maura like a complete ring, running all the way around the equipment and the children’s encampment. “We put food and stuff outside the line. Anna, or one of the others, collects it.”

“What happens if we cross the line?”

“We don’t know. The goons haven’t tried yet. They know what happened to that care worker. The bullet from the future.”

“The kids must sleep…”

“In shifts.” He pointed to the little huddle of sleeping forms. “Even now. They always have lookouts. And they move in clusters. It wouldn’t be possible to snatch one without others seeing, being close enough to react.” He scratched his beard thoughtfully. “There are some military-college types analyzing the patterns of the kids’ behavior. Turns out it’s very sophisticated. They work as if they are a single unit, but you don’t hear any of them giving commands or directing the others.”

“Then how? Telepathy?”

Dan shrugged. “They are all supersmart. Maybe they can all figure out the solution to this dynamic tactical problem. Maybe they just know.” He paused. “But it’s eerie to watch, Ms. Della. You can see the collective way they move. Like a pack.”

“Not human.”

“I guess not.”

The atmosphere here was one of tension and suspicion. An image came into her mind of Homo sapi children sitting around a fire, talking fast and fluidly, making fine tools and bows and arrows, surrounded by a circle of baffled and wary Neanderthal adults.

There was a sudden commotion on the other side of the lab: a brief scuffle, voices raised.

Somebody, an adult civilian, had stepped inside the blue chalk perimeter of the children’s domain. A couple of soldiers were reaching for him, weapons at their waist, but the intruder was out of reach.

“Oh, Christ,” Maura said.

It was Bill Tybee.

Little Torn came running out of the group of burger-munching kids, thin legs flashing. He ran straight to his father and clung to his legs, as if that were all that mattered, as if he were just some ordinary kid, and here was his father home from a day’s work.

Bill kneeled down. “You’ve got to come with me now, Tom. It’s over now. We’ll go back home, and wait for Mommy.”

As his father gently coaxed, Tom, clinging, was weeping loudly.

All around the room, Maura saw, weapons were being primed.

The girl Anna came forward now. Bill tensed, but let her approach the boy. Anna laid her own thin hand on Tom’s head. “Tom? You can go with your father if you want. You know that.”

Tom’s eyes were brimming pools of tears. His head tipped up; he looked from Anna to his father and back again. “I don’t want you to go, Dad.”

“But we both have to go.” Maura heard the effort Bill was making to keep his voice level. “Don’t you see? Everything will be fine. Your room is still there, just the way you left it.”

“No. Stay here.”

“I can’t.” Bill’s voice was breaking. “They are sending me away. The soldiers. I have to go now. And you have to come with me.”

“No—”

The girl stepped back. “Let him go, Mr. Tybee.”

Maura knew what was coming. Dread gathering blackly, she pushed forward; she got to the perimeter chalk line before she was stopped by a burly trooper. She called, “Bill. Come out of there.”

Bill grabbed the boy and straightened up, clutching Tom against his chest. “He’s my son. I can’t stand any more of this. Jesus, don’t any of you understand that?”

Maura said, as harshly as she could, “You have to let him go, Bill”

“No!” It was barely a word, more a roar of anger and pain. Holding Tom, Bill pulled away from Anna and tried to step out of the circle.

There was a flash.

Bill fell, screaming, grabbing at his leg.

Tom, released, tumbled; two children caught him and hauled him back to the center of the lab, out of reach.

Bill was on the ground, his lower right leg reduced to a mass of smashed flesh, shards of bone, a few tatters of cloth. A burly trooper in heavy body armor took a step forward, over the chalk line. He grabbed Bill around the waist — Maura heard the whir of hydraulics — and he hauled Bill bodily out of the blue circle, out of the room.

A trooper jumped on a table — a sergeant, Maura realized. “Let’s clear the room now, people. Let’s keep it orderly.”

“My God,” Dan Ystebo said.

Maura said, “Another bullet from the future?”

“The flash came from the bottle.” He pointed at the magnetic bottle at the end of the quark-nugget production line. “They shot him with a quark nugget.” He laughed, his voice strained. “They don’t need help from downstream any more.”

A trooper approached; they were hustled out of the room. But as she left, Maura couldn’t shut out of her head the sound of two people screaming: Bill Tybee, in the care of the paramedics, fighting to stay conscious; and his son, Tom, torn between warm past and chill future, a future he already knew his father couldn’t share.

And she knew, now, there were few options left.

Maura and Dan were restricted to a bunker a couple of miles from the center itself.

It was comfortable here: air-conditioned, clean, orderlies to serve coffee to the representative and her companion. But in the big central command, control, and communications room — C Cubed, as the military types called it — there was an air of tension.

Even though the target, monitored from a hundred angles, was just a group of eleven children, still confined to their blue-chalk circle. Just children: working, sleeping, eating, even playing. Eleven spindly, unwashed kids.

The first countermeasure was invisible.

When it was initiated some of the children — Maura counted them, four, five, six — fell down immediately. Maura could see them vomiting, and one little girl had a dark stain spreading over her backside as her bowels loosened. They were clutching their stomachs and crying — zoom in on twisted faces.

. Anna hauled the little ones into the big new cage they had built at the center of the heavy-water torus. As soon as they were inside the cage the children’s retching seemed to stop, and they immediately calmed. Anna sat the smallest girl on her lap and stroked her sweat-tangled hair.

Soon all the children were inside the cage, sitting or standing or lying. Anna led them in singing what sounded like a nursery rhyme.

“So much for that,” Dan said.

“What was it?”

“Deer savers,” he said. “Like on the hood of your car. Infrasound — very low frequency stuff. If you tune it right you can cause disorientation, nausea, even diarrhea. The FBI have been using it for years.”

“Good God almighty.”

“Every conspiracy nut knows about it. It was the best hope, in my opinion.”

“Hope of what?”

“Of a peaceful conclusion to this mess. But it didn’t work. Look at them. As soon as they got inside that cage of theirs they were immune. The cage is a barrier against infrasound.”

“Yes, and what else does it do?”

“I have a feeling we’ll find out. So… what next?”

Next turned out to be an invasion.

They kept the infrasound turned on for twelve hours. At least that kept the children trapped in their cage of steel and wire. Some of the kids managed to sleep, but there was no food in there, no water, no sanitation.

Then the troopers went in, eleven of them in their exo-suits: strictly SIPEs, for Soldier Integrated Protective Ensemble. They walked with a stiff, unnatural precision. Over each trooper’s head was a complex, insectile mask: a totally contained respiratory system, night-vision goggles, a heads-up display, even cute little sensors that would aim weapons the way the soldier happened to be looking.

Eleven supersoldiers, one for each superkid, stomping through grade-school corridors. Maura wondered what the troopers were feeling, how they had been briefed — how they were supposed to deal with this personally, even supposing they were successful.