The Oil Plague

Tally and David left at sunset.

Each of them rode two hoverboards. Pressed together like a sandwich, the paired boards could carry twice as much weight, most of it in saddlebags slung on the underside. They packed everything useful they could find, along with the magazines the Boss had saved. Whatever happened, there would be no point in returning to the Smoke.

Tally took the river down the mountain carefully, the extra weight swaying below her like a ball and chain around both ankles. At least she was wearing crash bracelets again.

Their journey would follow a path very different from the one Tally had taken there. That route had been designed to be easy to follow, and had included a helicopter ride with the rangers. This one wouldn't be as direct. Overloaded as they were, Tally and David couldn't manage even short distances on foot.

Every inch of the journey had to be over hoverable land and water, no matter how far it took them out of their way. And after the invasion, they would be giving any cities a wide berth.

Fortunately, David had made the journey to and from Tally's city dozens of times, alone and with inexperienced uglies in tow. He knew the rivers and rails, the ruins and natural veins of ore, and dozens of escape routes he'd devised in case he was ever pursued by city authorities.

"Ten days," he announced when they started. "If we ride all night and stay low during the day."

"Sounds good," Tally said, but she wondered if that would be soon enough to save anyone from the operation.

Around midnight the first night of travel, they left the brook that led down to the bald-headed hill, and followed a dry creek bed through the white flowers. It took them to the edge of a vast desert.

"How do we get through that?"

David pointed at dark shapes rising up from the sand, a row of them receding into the distance. "Those used to be towers, connected by steel cables."

"What for?"

"They carried electricity from a wind farm to one of the old cities."

Tally frowned. "I didn't know the Rusties used wind power."

"They weren't all crazy. Just most of them." He shrugged. "You've got to remember, we're mostly descended from Rusties, and we're still using their basic technology.Some of them must have had the right idea."

The cables still lay buried in the desert, protected by the shifting sands and a near-total absence of rainfall. In spots, they had broken or rusted through, so Tally and David had to ride carefully, eyes glued to the boards' metal detectors. When they reached a gap they couldn't jump, they would unroll a long piece of cable David carried, then walk the boards along it, guiding them like reluctant donkeys across some narrow footbridge before rolling it up again.

Tally had never seen a real desert before. She'd been taught in school that they were full of life, but this one was like the deserts she'd imagined as a littlie - featureless humps stretching into the distance, one after another. Nothing moved but slow snakes of sand borne by the wind.

She only knew the name of one big desert on the continent. "Is this the Mojave?"

David shook his head. "This isn't nearly that big, and it isn't natural. We're standing where the white weed started."

Tally whistled. The sand seemed to go forever. "What a disaster."

"Once the undergrowth was gone, replaced by the orchids, there was nothing to hold the good soil down. It blew away, and all that's left is sand."

"Will it ever be anything but desert?"

"Sure, in a thousand years or so. Maybe by then someone will have found a way to stop the weed from coming back. If we haven't, the process will just start all over again."

They reached a Rusty city around daybreak, a cluster of unremarkable buildings stranded on the sea of sand.

The desert had invaded over the centuries, dunes flowing through the streets like water, but the buildings were in better shape than other ruins Tally had seen. Sand wore away the edges of things, but it didn't tear them down as hungrily as rain and vegetation.

Neither of them was tired yet, but they couldn't travel during the day; the desert offered no protection from the sun, nor any concealment from the air. They camped in the second floor of a low factory building that still had most of its roof. Ancient machines, each as big as a hovercar, stood silent around them.

"What was this place?" Tally asked.

"I think they made newspapers here," David said. "Like books, but you threw them away and got a new one every day."

"You're kidding."

"Not at all. And you thought we wasted trees in the Smoke!"

Tally found a patch of sun shining through where the roof had collapsed, and unfolded the hoverboards to recharge. David pulled out two packets of EggSal.

"Will we make it out of the desert tonight?" she asked, watching David coax their last few drops of bottled water into the purifiers.

"No problem. We'll hit the next river before midnight."

She remembered something that Shay had said a long time ago, the first time she'd shown Tally her survival gear. "Can you really pee in a purifier? And then drink it, I mean?"

"Yeah. I've done it."

Tally grimaced and looked out the window. "Okay, I shouldn't have asked."

He came up behind her, laughing softly, placing his hands on her shoulders. "It's amazing what people will do to survive," he said.

She sighed. "I know."

The window overlooked a side street, partly protected from the encroaching desert. A few burned-out groundcars stood half-buried, their blackened frames stark against the white sand.

She rubbed the handcuff bracelets still encircling her wrists. "The Rusties sure wanted to survive. Every ruin I've seen, those cars are always all over, trying to get out. But they never seem to make it."

"A few of them did. But not in cars."

Tally leaned back into his reassuring warmth. The morning sun was hours away from burning off the chill of the desert.

"It's funny. At school, they never talk much about how it happened - the last panic, when the Rusty world fell apart. They shrug and say that all their mistakes just kept adding up, until it all collapsed like a house of cards."

"That's only partly true. The Boss had some old books about it."

"What did they say?"

"Well, the Rusties did live in a house of cards, but someone gave it a pretty big shove. No one ever found out who. Maybe it was a Rusty weapon that got out of control. Maybe it was people in some poor country who didn't like the way the Rusties ran things. Maybe it was just an accident, like the flowers, or some lone scientist who wanted to mess things up."

"But what happened?"

"A bug got loose, but it didn't infect people. It infected petroleum."

"Oil got infected?"

He nodded. "Oil is organic, made from old plants and dinosaurs and stuff. Somebody made a bacterium that ate it. The spores spread through the air, and when they landed in petroleum, processed or crude, they sprouted. Like a mold or something. It changed the chemical composition of the oil. Have you ever seen phosphorus?"

"It's an element, right?"

"Yeah. And it catches fire on contact with air."

Tally nodded. She remembered playing with the stuff in chem class, wearing goggles and talking about all the tricks you could do with it. But no one ever thought of a trick that wouldn't kill someone.

"Oil infected by this bacterium was just as unstable as phosphorus. It exploded on contact with oxygen.

And as it burned, the spores were released in the smoke, and spread on the wind. Until the spores got to the next car, or airplane, or oil well, and started growing again."

"Wow. And they used oil for everything, right?"

David nodded. "Like those cars down there. They must have been infected as they tried to get out of town."

"Why didn't they justwalk ?"

"Stupid, I guess."

Tally shivered again, but not from the cold. It was hard to think of the Rusties as actual people, rather than as just an idiotic, dangerous, and sometimes comic force of history. But there were human beings down there, whatever was left of them after a couple of hundred years, still sitting in their blackened cars, as if still trying to escape their fate.

"I wonder why they don't tell us that in history class. They usually love any story that makes the Rusties sound pathetic."

David lowered his voice. "Maybe they didn't want you to realize that every civilization has its weakness.

There's always one thing we depend on. And if someone takes it away, all that's left is some story in a history class."

"Not us," she said. "Renewable energy, sustainable resources, a fixed population."

The two purifierspinged, and David left her to get them. "It doesn't have to be about economics," he said, bringing the food over. "The weakness could be an idea."

She turned to take her EggSal, cupping its warmth in her hands, and saw how serious he looked. "So, David, is that one of the things you thought about all those years, when you imagined the Smoke being invaded? Did you ever wonder what would turn the cities into history?"

He smiled and took a big bite.

"It gets clearer every day."