Sam and Bruiser climbed the mountain trail. It was thin and winding, sized for the two teenagers who created it. It led upward from their village in the valley below. Now and then, they would stop for a break and use their hatchets to cut back some of the overgrowth. Ostensibly, the pair had been sent to find rabbits. But those were scarce enough these days, and the mood to explore had taken over.

Bruiser puffed out his chest. "I hope we meet one of those raiding parties from the next valley. I'd love to see what happens if they have to stand and fight."

Sam just gave an encouraging smile, not letting what she thought of that show. There were raiding parties, but the valley they were theorized to be from was in the opposite direction from their little rabbit trail. Besides, their only weapons were slingshots and hatchets. Against a full raiding party, she certainly wouldn't be staying around.

"Yeah, as soon as they nail down their location, I'll go over with my dad and the other adult hunters, and slaughter the lot of them. It'll be nice for our village to have a second valley."

If they were forced into raiding, then their farms must be failing. If anything, a second valley would be a burden. Distant records told of conquerors and alliances ruling multiple valleys, but the barriers of the mountains and harsh winters broke things down in the end. The trees grew quickly, and leaving a trail empty for an entire season guaranteed it would be gone by the time you returned.

Sam kept climbing, listening passively to Bruiser's boasting. She kept her eyes on the sky.

There was only one real mystery in Sam's life. Every few nights, red and white lights crossed the sky. She had always hoped they would appear during the day so she could see them better.

Bruiser let out a yelp, and vanished.

Sam, pulled back into the moment, quickly looked around and saw a dark hole where he had been standing.

"Bruiser!"

"I'm okay!" came a muffled reply. "But there are a few different tunnels down here, and I don't know which one I came from. Keep yelling!"

Sam yelled for a few minutes, feeling awkward. If a raiding party really had been in the neighborhood, they would have been able to find her easily. Thankfully it was just the rabbits. Eventually, Bruiser climbed out of the hole, covered in dirt.

"We need to go back down there." Bruiser was serious for once, not mooning around after glory.

"Why? You find a rabbit's den?"

"No. But it's weird. Come see."

The two used their hatchets to make deep marks in the dirt, and climbed down slower than Bruiser's initial fall. The tunnel sloped downward, and got both steeper and wider as they continued, though never enough that they didn't think they could climb back up.

And then the tunnel changed. They rounded a corner, and the dirt became some sort of shiny stone. The stone echoed when Bruiser stomped on it. Small glowing rocks were embedded in the ceiling, lighting the tunnel. It was high enough now that an adult could have stood upright.

"See? Weird!" Bruiser said.

Sam nodded. Couldn't argue there.

The two followed the new tunnel, too nervous to talk much. There were doors made out of the same shiny stone, on alternating sides of the tunnel every few meters.

 After a few minutes of walking, Bruiser tried one, and to his visible surprise, it opened. Inside was a row of walls, with lines crisscrossing each, and pictures of trees in the boxes the lines formed. Sam touched one of the boxes, and it popped open. It was a drawer full of seeds. Each wall must have been full of them. There were other markings inside the drawer, but neither of them could read.

"Nice, nice. Not bad," Bruiser said. "Whoever made this stored some food for us."

Sam popped open another drawer, and observed the difference between the seeds. For once she felt compelled to correct her friend's assumptions.

"I think these are all different kinds of plants, actually. Not for eating, but for making more food."

Bruiser thought about it, and nodded. "Also nice. But there must be better stuff in the other rooms."

The next room was full of cylinders on shelves with pictures of vegetables and beans, though not the varieties Sam was used to.

"More seeds! Boring!" Bruiser shut the door.

The third room had rectangles on shelves, and initially Sam thought they must be little boxes, perhaps containing more seeds. But after picking one up, it fell open, and she saw that it was some sort of object for storing markings. Markings that they couldn't read. Her dad could. They would have to come back here with him sometime.

She looked through and found a few thinner marking-holders that had pictures. They were of staggering quality. The trees and vegetables had been little cartoons, understandable but not realistic. The pictures in the marking-holders must have taken years to complete. She held them close to her chest.

"This must be a Predecessor cave. It's too clean to be anything else. But one thing we know about Predecessors is they had way better weapons. Where are they?" Bruiser grumbled to himself.

Sam let him talk and looked through the pictures. She didn't understand most of them, but they were fascinating regardless. She kept hoping she would see something recognizable, and feel a connection to them.

Then suddenly, she did.

The next few rooms were living quarters, all empty. Whoever built the place never got a chance to move in.

Then, finally.

"That's an atomic bomb," Bruiser said, satisfied at last.

The room was full of black metal rods. Some were short enough for Sam to hold in their hand; some were longer than her arm. Some were odder shapes, and some looked too heavy for her to lift.

"How do you know?"

"I don't know a lot, but I know an atomic bomb when I see one. These fire out bullets, little hunks of metal that kill you and make your kids sick for years after."

"How do they know the difference between my kids and someone else's kids?"

Bruiser shrugged. "The Predecessors worked in mysterious ways."

He picked up one of the short ones, wrapping his fingers around the grip. "I am going to kill every last one of the raiders."

Sam realized that for once Bruiser might not be all talk. The raiders couldn't stand up to Predecessor weaponry.

"Bruiser, you don't want to do that. The raiders haven't killed anyone; they're probably just starving. Our village has enough food anyway."

Bruiser frowned. "You never said anything like this before. I thought you had my back."

"Well, before I didn't think you could actually, you know, do it."

"I could have!" He glared at her. "It'll just be easier with this." He pointed the atomic bomb at her.

Sam flinched out of the way. "Careful! You don't know what sets it off yet."

He put it back to his side. "Calm down, I had it on stun."

Sam took her own atomic bomb, and they went further down the tunnel. She kept thinking about the picture she had seen earlier, and about what was going to happen to those poor raiders.

The picture had been a night sky, with the red and white lights she always saw. But visible this time, was a long white cross with the arms angled toward the tail. Through the other pictures in the book, she managed to figure out it was some sort of Predecessor vehicle.

A Predecessor vehicle that flew through the night sky every few days.

The Predecessors weren't gone. Sam's village just hadn't left the valley in so long that they'd been forgotten. Sam could leave the valley to go find them.

Still, she didn't want to be responsible for the death of those raiders. Maybe she could take Bruiser with her?

They hadn't passed a door in quite some time. Then they found one, not in the side, but in the end of the tunnel. It opened to a place Sam recognized as much further down the mountain, practically in the village proper.

"Wow, who knew all this was here this whole time," Bruiser said. He grinned. "Time to go get the other hunters."

Sam panicked. She could convince Bruiser if she had time. But all of her time was suddenly up. She just needed to keep Bruiser here a little longer.

She lifted the atomic bomb. According to Bruiser, it was set to stun.