Ninety-seven percent of four billion? You do the math.

That’s when the Alien Empire descended in their flying saucers and started blasting away, right? When the peoples of the Earth united under one banner to play David versus Goliath. Our tanks against your ray guns. Bring it on!

We weren’t that lucky.

And they weren’t that stupid.

How do you waste nearly four billion people in three months?

Birds.

How many birds are there in the world? Wanna guess? A million? A billion? How about over three hundred billion? That’s about seventy-five birds for each man, woman, and child still alive after the first two waves.

There are thousands of species of bird on every continent. And birds don’t recognize borders. They also crap a lot. They crap five or six times a day. That’s over a trillion little missiles raining down each day, every day.

You couldn’t invent a more efficient delivery system for a virus that has a 97 percent kill rate.

My father thought they must have taken something like Ebola Zaire and genetically altered it. Ebola can’t spread through the air. But change a single protein and you can make it airborne, like the flu. The virus takes up residence in your lungs. You get a bad cough. Fever. Your head starts to hurt. Hurt bad. You start spitting up little drops of virus-laden blood. The bug moves into your liver, your kidneys, your brain. You’re packing a billion of them now. You’ve become a viral bomb. And when you explode, you blast everyone around you with the virus. They call it bleeding out. Like rats fleeing a sinking ship, the virus erupts out of every opening. Your mouth, your nose, your ears, your ass, even your eyes. You literally cry tears of blood.

We had different names for it. The Red Death or the Blood Plague. The Pestilence. The Red Tsunami. The Fourth Horseman. Whatever you wanted to call it, after three months, ninety-seven out of every hundred people were dead.

That’s a lot of bloody tears.

Time was flowing in reverse. The 1st Wave knocked us back to the eighteenth century. The next two slammed us into the Neolithic.

We were hunter-gatherers again. Nomads. Bottom of the pyramid.

But we weren’t ready to give up hope. Not yet.

There were still enough of us left to fight back.

We couldn’t take them head-on, but we could fight a guerilla war. We could go all asymmetrical on their alien asses. We had enough guns and ammo and even some transport that survived the 1st Wave. Our militaries had been decimated, but there were still functional units on every continent. There were bunkers and caves and underground bases where we could hide for years. You be America, alien invaders, and we’ll be Vietnam.

And the Others go, Yeah, okay, right.

We thought they had thrown everything at us—or at least the worst, because it was hard to imagine anything worse than the Red Death. Those of us who survived the 3rd Wave—the ones with a natural immunity to the disease—hunkered down and stocked up and waited for the People in Charge to tell us what to do. We knew somebody had to be in charge, because occasionally a fighter jet would scream across the sky and we heard what sounded like gun battles in the distance and the rumble of troop carriers just over the horizon.

I guess my family was luckier than most. The Fourth Horseman rode off with my mom, but Dad, Sammy, and I survived. Dad boasted about our superior genes. Not something you’d normally do, brag on top of an Everest of nearly seven billion dead people. Dad was just being Dad, trying to put the best spin he could on the eve of human extinction.

Most cities and towns were abandoned in the wake of the Red Tsunami. There was no electricity, no plumbing, the shops and stores had long since been looted of anything valuable. Raw sewage was an inch deep on some streets. Fires from summer lightning storms were common.

Then there was the problem of the bodies.

As in, they were everywhere. Houses, shelters, hospitals, apartments, office buildings, schools, churches and synagogues, and warehouses.

There’s a tipping point when the sheer volume of death overwhelms you. You can’t bury or burn the bodies fast enough. That summer of the Pestilence was brutally hot, and the stench of rotting flesh hung in the air like an invisible, noxious fog. We soaked strips of cloth in perfume and tied them over our mouths and noses, and by the end of the day the reek had soaked into the material and all you could do was sit there and gag.

Until—funny thing—you got used to it.

We waited out the 3rd Wave barricaded inside our house. Partly because there was a quarantine. Partly because some pretty whacked-out people roamed the streets, breaking into houses and setting fires, the whole murder, rape, and pillaging thing. Partly because we were scared out of our minds waiting for what might come next.

But mostly because Dad didn’t want to leave Mom. She was too sick to travel, and he couldn’t bring himself to abandon her.

She told him to go. Leave her behind. She was going to die anyway. It wasn’t about her anymore. It was about me and Sammy. About keeping us safe. About the future and hanging on to the hope that tomorrow would be better than today.

Dad didn’t argue. But he didn’t leave her, either. He waited for the inevitable, keeping her as comfortable as possible, and looked at maps and made lists and gathered supplies. This was around the time the whole book-hoarding, we-have-to-rebuild-civilization kick started. On nights when the sky wasn’t totally blanketed in smoke, we went into the backyard and took turns with my old telescope, watching the mothership sail majestically across the backdrop of the Milky Way. The stars were brighter now, brilliantly bright, without our man-made lights to dim them.

“What are they waiting for?” I would ask him. I was still expecting—like everybody else—the saucers and the mechanical walkers and the laser cannons. “Why don’t they just get it over with?”

And Daddy would shake his head. “I don’t know, pumpkin,” he would say. “Maybe it is over. Maybe the goal isn’t to kill all of us, just wean us down to a manageable number.”

“And then what? What do they want?”

“I think the better question is what they need,” he said gently, as if he were breaking some really bad news. “They’re being very careful, you know.”

“Careful?”

“To not damage it more than absolutely necessary. It’s the reason they’re here, Cassie. They need the Earth.”

“But not us,” I whispered. I was about to lose it—again. For about the trillionth time.

He put his hand on my shoulder—for about the trillionth time—and said, “Well, we had our shot. And we weren’t handling our inheritance very well. I bet if we could somehow go back and interview the dinosaurs before the asteroid struck…”

That’s when I punched him as hard as I could. Ran inside.

I don’t know which is worse, inside or outside. Outside you feel totally exposed, constantly watched, naked beneath the naked sky. But inside it’s perpetual twilight. Boarded-up windows that block out the sun during the day. Candles at night, but we’re running low on candles, can’t spare more than one per room, and deep shadows lurk in once-familiar corners.

“What is it, Cassie?” Sammy. Five. Adorable. Big brown teddy-bear eyes, clutching the other member of the family with big brown eyes, the stuffed one I now have stowed in the bottom of my backpack.

“Why are you crying?”

Seeing my tears got his started.

I brushed past him, headed for the room of the sixteen-year-old human dinosaur, Cassiopeia Sullivanus extinctus. Then I went back to him. I couldn’t leave him crying like that. We’d gotten pretty tight since Mom got sick. Nearly every night bad dreams chased him into my room, and he’d crawl in bed with me and press his face against my chest, and sometimes he forgot and called me Mommy.