"Oh my God, we have to go back for Dad," Brent howled, beating on his sister's back. She had thrown him over his shoulder and he could see behind them - all he could see was the dark mouth of the cylinder, and a hint of green fire inside. "We have to go back!"

"Brent," Maggie said, very quietly.

"We have to! He could be really badly hurt! Turn around, Mags!"

"Brent."

"He probably can't walk, but we can make a travois, it's only a couple of hours back to the car and then, and then we can drive to a hospital, it's a long way, but - "

"Brent!"

"Just put me down, and I'll go back for him, I know he was really hurt, I know it looked really bad, but you gotta - Mags - you gotta go back and - "

"Brent, please," she said, and stopped running. She knelt down and laid him gently on the ground. "Please stop. Please just stop and think for a second."

He fought her. He fought as hard as he could, because his dad's life depended on it. "No," he said, and shook his head. He felt like a baby refusing to eat mushed peas. He felt immature and like he wasn't being realistic, but - Dad! Dad was back there!

"He's dead," Maggie said. Over and over until he started believing it. "Dad's dead."

When he opened his eyes again they were walking through the desert. The sun had set and the moon was up. He shook himself, unable to understand how he'd gotten there - a lot of time had to have passed but it felt like he'd just closed his eyes for a second. It was like his brain had just shut off, turned itself off because it couldn't handle what was going on, and he had just started walking, his body moving by autopilot.

He stopped in his tracks. After a second, Maggie, who was a couple strides ahead of him, stopped too. "Where are we going?" Brent asked.

"Back to the camp. I need to make a phone call. Listen, Brent, you need to let me be in charge right now, okay?"

"I want to go back." When she sighed he shook his head. "I know he's dead, now. But I want to find out why. You and I got burned too, but I don't feel like I'm hurt, and you look just fine."

She stared at him for a while. Then she said, "Better than fine."

He didn't understand.

In a slow, steady voice, the kind adults use when explaining complex things to children, she said, "I had a pimple. On my neck. It was there this morning. It was almost ready to pop, but not quite. It kind of hurt, especially when I got out in the sun and started sweating." She lifted her hair away from her neck and showed him the clear, unblemished skin there. "No pimple now."

"That green fire - burned off your zit?" he asked.

"Something did. And I had blisters on my feet, too, because these boots are a year old and my feet got bigger since we bought them. The blisters hurt like hell."

"And?"

She rolled her eyes. "They're gone now. My feet still feel squashed. But it doesn't hurt anymore."

Brent touched the underside of his chin. He had cut himself shaving there the day before. It was one of his first times shaving and he hadn't gotten used to it yet. The nick and the razorburn had been agonizing in the desert heat. Now they were gone.

"What does it mean?" Brent asked.

"I have no clue!" Maggie shouted. Her voice rolled across the landscape, echoing off a line of cliffs. "Let me be in charge, okay? I promise I'll keep you safe. I'll get you home."

Brent's throat closed up suddenly and he wondered if it was a delayed reaction to the green fire, if he was suddenly dying. But no. A tear worked its way out of the side of his eye. "Home," he croaked. "We don't have a home anymore. We're - "

"Orphans," she said. "Yeah. Which means we have to stick together. And because I'm the oldest that means I'm in charge and you do what I say. Got it?"

He nodded carefully.

They didn't go back. Instead they pressed on, toward the camp. The desert by moonlight was made of silver in a million different shades. There was enough light to see where they were putting their feet, but they stayed clear of the long shadows that were impenetrably dark.

It was a long hike. They should have been asleep by now, safely wrapped up in their sleeping bags. Even when they got to the camp, they would just load everything up in the car and head back to town, to civilization. To a lot of questions they couldn't answer. Brent kind of wished his brain would shut down again, but it didn't.

He heard a rock collide with another rock in the darkness, a soothing Tchok! and then a rattle as the rock bounced and rolled and settled down. He looked ahead and saw Maggie holding a handful of small stones worn perfectly smooth by the water that had left the desert behind thousands of years ago.

She threw another one, underhand. It went farther this time and the sounds were less clear.

"What are you doing?" he asked.

"Scaring off coyotes. I don't know! I'm just - it helps me not think."

"Can I try?" Brent asked.

"You've got two hands. Get your own rocks."

He bent and picked up a pile of smooth stones for himself. He tossed one at a cactus plant about fifty yards away. One arm of the cactus creaked and then fell off.

"I didn't mean to do that," he said, putting a hand over his mouth.

"It's just a cactus," Maggie said. "There are lots of them." She threw one of her own rocks at the plant and another arm came off. Water trickled sluggishly down its trunk, brilliant in the moonlight.

"Hold on," Brent said. There was something weird about this. He picked up a slightly larger stone, about the size of a golf ball. He picked another cactus, wound up, and threw the stone as hard as he could.

There was a noise like a gun going off. He had missed the cactus by a few yards. Instead the stone hit the ground in front of it. Dirt and sand flew up in huge sprays and the stone dug a deep crater in the ground. Brent ran over to the hole in the ground and reached inside to find the rock. It was buried a foot down, and it was hot to the touch when he brought it up into the night air.

"Maggie," he said, "I think we - "

He looked back and saw his sister holding a rock as big as a beach ball. It must have weighed a hundred pounds, he thought, at least. It occurred to him that he hadn't wondered at all how she was able to throw him over her shoulder and carry him out of the cylinder when he was, in fact, a little taller and a lot heavier than she was.

"Mags, don't hurt yourself," Brent said.

Maggie spun from the waist and hurled the boulder out into the night. Brent watched it fly as far as he could before he lost it in the darkness. It hadn't started coming down again when he lost sight of it. Neither of them heard it land.