It’s hard to plan for what comes next when what comes next is not something you planned for.

Try to spot them first, I decided. Take cover. No showdowns. No more Crucifix Soldiers!

The day is bright and windless but cold. The sky cloudless. Walking along, bobbing my head up and down, swinging it from side to side, backpack popping against one shoulder blade, the rifle against the other, walking on the outside edge of the median that separates the southbound from the northbound lanes, stopping every few strides to whip around and scan the terrain behind me. An hour. Two. And I’ve traveled no more than a mile.

The creepiest thing, creepier than the abandoned cars and the snarl of crumpled metal and the broken glass sparkling in the October sunlight, creepier than all the trash and discarded crap littering the median, most of it hidden by the knee-high grass so the strip of land looks lumpy, covered in boils, the creepiest thing is the silence.

The Hum is gone.

You remember the Hum.

Unless you grew up on top of a mountain or lived in a cave your whole life, the Hum was always around you. That’s what life was. It was the sea we swam in. The constant sound of all the things we built to make life easy and a little less boring. The mechanical song. The electronic symphony. The Hum of all our things and all of us. Gone.

This is the sound of the Earth before we conquered it.

Sometimes in my tent, late at night, I think I can hear the stars scraping against the sky. That’s how quiet it is. After a while it’s almost more than I can stand. I want to scream at the top of my lungs. I want to sing, shout, stamp my feet, clap my hands, anything to declare my presence. My conversation with the soldier had been the first words I’d said aloud in weeks.

The Hum died on the tenth day after the Arrival. I was sitting in third period texting Lizbeth the last text I will ever send. I don’t remember exactly what it said.

Eleven A.M. A warm, sunny day in early spring. A day for doodling and dreaming and wishing you were anywhere but Ms. Paulson’s calculus class.

The 1st Wave rolled in without much fanfare. It wasn’t dramatic. There was no shock and awe.

The lights just winked out.

Ms. Paulson’s overhead died.

The screen on my phone went black.

Somebody in the back of the room squealed. Classic. It doesn’t matter what time of day it happens—the power goes out, and somebody yelps like the building’s collapsing.

Ms. Paulson told us to stay in our seats. That’s the other thing people do when the power goes out. They jump up to…To what? It’s weird. We’re so used to electricity, when it’s gone, we don’t know what to do. So we jump up or squeal or start jabbering like idiots. We panic. It’s like someone cut off our oxygen. The Arrival had made it worse, though. Ten days on pins and needles waiting for something to happen while nothing is happening makes you jumpy.

So when they pulled the plug on us, we freaked a little more than normal.

Everybody started talking at once. When I announced that my phone had died, out came everyone’s dead phone. Neal Croskey, who was sitting in the back of the room listening to his iPod while Ms. Paulson lectured, pulled the buds from his ears and wondered aloud why the music had died.

The next thing you do when the plug’s pulled, after panicking, is run to the nearest window. You don’t know why exactly. It’s that better-see-what’s-going-on feeling. The world works from the outside in. So if the lights go off, you look outside.

And Ms. Paulson, randomly moving around the mob milling in front of the windows: “Quiet! Back to your seats. I’m sure there’ll be an announcement…”

There was one, about a minute later. Not over the intercom, though, and not from Mr. Faulks, the vice principal. It came from the sky, from them. In the form of a 727 tumbling end over end to the Earth from ten thousand feet until it disappeared behind a line of trees and exploded, sending up a fireball that reminded me of the mushroom cloud of an atomic blast.

Hey, Earthlings! Let’s get this party started!

You’d think seeing something like that would send us diving under our desks. It didn’t. We crowded against the window and scanned the cloudless sky for the flying saucer that must have taken the plane down. It had to be a flying saucer, right? We knew how a top-notch alien invasion was run. Flying saucers zipping through the atmosphere, squadrons of F-16s hot on their heels, surface-to-air missiles and tracers screaming from the bunkers. In an unreal and admittedly sick way, we wanted to see something like that. It would make this a perfectly normal alien invasion.

For a half hour we waited by the windows. Nobody said much. Ms. Paulson told us to go back to our seats. We ignored her. Thirty minutes into the 1st Wave and already social order was breaking down. People kept checking their phones. We couldn’t connect it: the plane crashing, the lights going out, our phones dying, the clock on the wall with the big hand frozen on the twelve, little hand on the eleven.

Then the door flew open and Mr. Faulks told us to head over to the gym. I thought that was really smart. Get all of us in one place so the aliens didn’t have to waste a lot of ammunition.

So we trooped over to the gym and sat in the bleachers in near total darkness while the principal paced back and forth, stopping every now and then to yell at us to be quiet and wait for our parents to get there.

What about the students whose cars were at school? Couldn’t they leave?

“Your cars won’t work.”

WTF? What does he mean, our cars won’t work?

An hour passed. Then two. I sat next to Lizbeth. We didn’t talk much, and when we did, we whispered. We weren’t afraid of the principal; we were listening. I’m not sure what we were listening for, but it was like that quiet before the clouds open up and the thunder smashes down.

“This could be it,” Lizbeth whispered. She rubbed her nose nervously. Dug her lacquered nails into her dyed blond hair. Tapped her foot. Rolled the pad of her finger over her eyelid: She had just started wearing contacts and they bugged her constantly.

“It’s definitely something,” I whispered back.

“I mean, this could be it. Like it it. The end.”

She kept slipping the battery out of her phone and putting it back in. It was better than doing nothing, I guess.

She started to cry. I took her phone away and held her hand. Looked around. She wasn’t the only one crying. Other kids were praying. And others were doing both, crying and praying. The teachers were huddled up by the gym doors, forming a human shield in case the creatures from outer space decided to storm the floor.

“There’s so much I wanted to do,” Lizbeth said. “I’ve never even…” She choked back a sob. “You know.”

“I’ve got a feeling a lot of ‘you know’ is going on right now,” I said. “Probably right underneath these bleachers.”

“You think?” She wiped her cheeks with the palm of her hand. “What about you?”

“About ‘you know’?” I had no problem with talking about sex. My problem was talking about sex as it related to me.

“Oh, I know you haven’t ‘you know.’ God! I’m not talking about that.”

“I thought we were.”

“I’m talking about our lives, Cassie! Jesus, this could be the end of the freakin’ world, and all you want to do is talk about sex!”

She pulled her phone out of my hand and fumbled with the battery cover.

“Which is why you should just tell him,” she said, fiddling with the drawstrings of her hoodie.

“Tell who what?” I knew exactly what she meant; I was just buying time.

“Ben! You should tell him how you feel. How you’ve felt since the third grade.”

“This is a joke, right?” I felt my face getting hot.

“And then you should have sex with him.”

“Lizbeth, shut up.”

“It’s the truth.”

“I haven’t wanted to have sex with Ben Parish since the third grade,” I whispered. The third grade? I glanced over at her to see if she was really listening. Apparently, she wasn’t.

“If I were you, I’d go right up to him and say, ‘I think this is it. This is it, and I’ll be damned if I’m going to die in this school gymnasium without ever having sex with you.’ And then you know what I’d do?”

“What?” I was fighting back a laugh, picturing the look on his face.

“I’d take him outside to the flower garden and have sex with him.”

“In the flower garden?”

“Or the locker room.” She waved her hand around frantically to include the entire school—or maybe the whole world. “It doesn’t matter where.”

“The locker room smells.” I looked two rows down at the outline of Ben Parish’s gorgeous head. “That kind of thing only happens in the movies,” I said.

“Yeah, totally unrealistic, not like what’s happening right now.”

She was right. It was totally unrealistic. Both scenarios, an alien invasion of the Earth and a Ben Parish invasion of me.

“At least you could tell him how you feel,” she said, reading my mind.

Could, yes. Ever would, well…

And I never did. That was the last time I saw Ben Parish, sitting in that dark, stuffy gymnasium (Home of the Hawks!) two rows down from me, and only the back part of him. He probably died in the 3rd Wave like almost everybody else, and I never told him how I felt. I could have. He knew who I was; he sat behind me in a couple of classes.

He probably doesn’t remember, but in middle school we rode the same bus, and there was an afternoon when I overheard him talking about his little sister being born the day before and I turned around and said, “My brother was born last week!” And he said, “Really?” Not sarcastic, but like he thought it was a cool coincidence, and for about a month I went around thinking we had this special connection based on babies. Then we were in high school and he became the star wide receiver for the team and I became just another girl watching him score from the stands. I would see him in class or in the hallway, and sometimes I had to fight the urge to run up to him and say, “Hi, I’m Cassie, the girl from the bus. Do you remember the babies?”

The funny thing is, he probably would have. Ben Parish couldn’t be satisfied with being the most gorgeous guy in school. Just to torment me with his perfection, he also insisted on being one of the smartest. And have I mentioned he was kind to small animals and children? His little sister was on the sidelines at every game, and when we took the district title, Ben ran straight to the sidelines, hoisted her onto his shoulders, and led the parade around the track with her waving to the crowd like a homecoming queen.

Oh, and one more thing: his killer smile. Don’t get me started.

After another hour in the dark and stuffy gym, I saw my dad appear in the doorway. He gave a little wave, like he showed up at my school every day to take me home after alien attacks. I hugged Lizbeth and told her I’d call as soon as the phones started working again. I was still practicing pre-invasion thinking. You know, the power goes out, but it always comes back on. So I just gave her a hug and I don’t remember telling her that I loved her.