When it did, a child emerged, and the stillness of the waiting was broken. The woman ran from the porch and shoved the barrel of the rifle down. He’s just a baby. Would you shoot a child? And the man’s face was twisted with indecision and the rage of everything ever taken for granted betrayed. How do we know? he demanded of the woman. How can we be sure of anything anymore? The child stumbled from the wheat and fell. The woman ran to him and scooped him up, pressing the boy’s filthy face against her breast, and the man with the gun stepped in front of her. He’s freezing. We have to get him inside. And the man felt a great pressure inside his chest. He was squeezed between what the world had been and what the world had become, who he was before and who he was now, and the cost of all the unspoken promises weighing on his heart. He’s just a baby. Would you shoot a child? The woman walked past him, up the steps, onto the porch, into the house, and the man bowed his head as if in prayer, then lifted his head as if in supplication. He waited a few minutes to see if anyone else emerged from the wheat, for it seemed incredible to him that a toddler might survive this long, alone and defenseless, with no one to protect him. How could such a thing be possible?

When he stepped inside the parlor of the old farmhouse, he saw the woman holding the child in her lap. She had wrapped a blanket around him and brought him water, little fingers slapped red by the cold wrapped around the cup, and the others had gathered in the room and no one spoke, but they stared at the child with dumbstruck wonder. How could such a thing be? The child whimpered. His eyes skittered from face to face, searching for the familiar, but they were strangers to him as they had been strangers to one another before the world ended. He whined that he was cold and said that his throat hurt. He had a bad owie in his throat.

The woman holding him prodded the child to open his mouth. She saw the inflamed tissue at the back of his mouth, but she did not see the hair-thin wire embedded near the opening of his throat. She could not see the wire or the tiny capsule connected to the wire’s end. She could not know, as she bent over the child to peer into his mouth, that the device inside the child was calibrated to detect the carbon dioxide in her breath.

Our breath the trigger.

Our child the weapon.

The explosion vaporized the old farmhouse instantly.

The wheat took longer. Nothing was left of the farmhouse or the outbuildings or the silo that in every other year had held the abundant harvest. But the dry, lithe stalks consumed by fire turned to ash, and at sunset, a stiff northerly wind swept over the prairie and lifted the ash into the sky and carried it hundreds of miles before the ash came down, a gray and black snow, to settle indifferently on barren ground.

BOOK ONE

1

THE WORLD IS a clock winding down.

I hear it in the wind’s icy fingers scratching against the window. I smell it in the mildewed carpeting and the rotting wallpaper of the old hotel. And I feel it in Teacup’s chest as she sleeps. The hammering of her heart, the rhythm of her breath, warm in the freezing air, the clock winding down.

Across the room, Cassie Sullivan keeps watch by the window. Moonlight seeps through the tiny crack in the curtains behind her, lighting up the plumes of frozen breath exploding from her mouth. Her little brother sleeps in the bed closest to her, a tiny lump beneath the mounded covers. Window, bed, back again, her head turns like a pendulum swinging. The turning of her head, the rhythm of her breath, like Nugget’s, like Teacup’s, like mine, marking the time of the clock winding down.

I ease out of bed. Teacup moans in her sleep and burrows deeper under the covers. The cold clamps down, squeezing my chest, though I’m fully dressed except for my boots and the parka, which I grab from the foot of the bed. Sullivan watches as I pull on the boots, then when I go to the closet for my rucksack and rifle. I join her by the window. I feel like I should say something before I leave. We might not see each other again.

“So this is it,” she says. Her fair skin glows in the milky light. The spray of freckles seems to float above her nose and cheeks.

I adjust the rifle on my shoulder. “This is it.”

“You know, Dumbo I get. The big ears. And Nugget, because Sam is so small. Teacup, too. Zombie I don’t get so much—Ben won’t say—and I’m guessing Poundcake has something to do with his roly-poly-ness. But why Ringer?”

I sense where this is going. Besides Zombie and her brother, she isn’t sure of anyone anymore. The name Ringer gives her paranoia a nudge. “I’m human.”

“Yeah.” She looks through the crack in the curtains to the parking lot two stories below, shimmering with ice. “Someone else told me that, too. And, like a dummy, I believed him.”

“Not so dumb, given the circumstances.”

“Don’t pretend, Ringer,” she snaps. “I know you don’t believe me about Evan.”

“I believe you. It’s his story that doesn’t make sense.”

I head for the door before she tears into me. You don’t push Cassie Sullivan on the Evan Walker question. I don’t hold it against her. Evan is the little branch growing out of the cliff that she clings to, and the fact that he’s gone makes her hang on even tighter.

Teacup doesn’t make a sound, but I feel her eyes on me; I know she’s awake. I go back to the bed.

“Take me with you,” she whispers.

I shake my head. We’ve been through this a hundred times. “I won’t be gone long. A couple days.”

“Promise?”

No way, Teacup. Promises are the only currency left. They must be spent wisely. Her bottom lip quivers; her eyes mist. “Hey,” I say softly. “What did I tell you about that, soldier?” I resist the impulse to touch her. “What’s the first priority?”

“No bad thoughts,” she answers dutifully.

“Because bad thoughts do what?”

“Make us soft.”

“And what happens if we go soft?”

“We die.”

“And do we want to die?”

She shakes her head. “Not yet.”

I touch her face. Cold cheek, warm tears. Not yet. With no time left on the human clock, this little girl has probably reached middle age. Sullivan and me, we’re old. And Zombie? The ancient of days.

He’s waiting for me in the lobby, wearing a ski jacket over a bright yellow hoodie, both scavenged from the remains inside the hotel: Zombie escaped from Camp Haven wearing only a flimsy pair of scrubs. Beneath his scruffy beard, his face is the telltale scarlet of fever. The bullet wound I gave him, ripped open in his escape from Camp Haven and patched up by our twelve-year-old medic, must be infected. He leans against the counter, pressing his hand against his side and trying to look like everything’s cool.

“I was starting to think you changed your mind,” Zombie says, dark eyes sparkling as if he’s teasing, though that could be the fever.

I shake my head. “Teacup.”

“She’ll be okay.” To reassure me, he releases his killer smile from its cage. Zombie doesn’t fully appreciate the pricelessness of promises or he wouldn’t toss them out so casually.

“It’s not Teacup I’m worried about. You look like shit, Zombie.”