Max's voice came over an intercom. "Hey folks, we're taking off in two minutes so you better strap yourself in 'til I have the motion stabilizers on."

Abbey rushed over and strapped herself into one of the chairs. Caleb and Simon didn't follow.

"Hey, I bet that's a window," Caleb said, pointing.

On the wall opposite the door into the computer room was a large, rounded rectangular outline, like a window on an airplane. Abbey watched Simon and Caleb walk over and look at it.

"What are you doing? What if that's a door to the outside?" Abbey asked.

Caleb scrunched up his face. "A two-foot-high door, two feet off the ground?"

"Take off in one minute," the computer said.

"It could be a door to another compartment. You two better get strapped in."

"It's got to be a window," said Simon, pointing to a control panel with two b.u.t.tons next to the outline. He pressed the top b.u.t.ton. The blind slid open, revealing a gla.s.sed-in window with a view of the causeway and the metallic building set into the hillside.

Caleb and Simon plunked themselves into two of the remaining seats just as the vessel detached from the causeway and climbed into the air. The takeoff was surprisingly smooth and fast. They stared out the window at the rapidly disappearing causeway. Once aloft, the vessel rolled sharply to the left. Simon's backpack, which he'd removed when they'd entered the room, flew against the wall with a thud. They now had a bird's-eye view of the city. The rail tracks extended out of the city in several directions with tiny monorail-type trains moving at a rapid pace. The river formed lazy S-curve loops as it wound through the city.

"It all looks familiar somehow," Abbey murmured, more to herself than to her brothers. The vessel began moving in a smooth forward and upward direction. She started to relax slightly, when all of a sudden the vessel shot forward. She clutched the armrests as she was pressed back into her seat. She couldn't even turn her head to look at Simon and Caleb. She ran the numbers in her mind. Trained astronauts can tolerate up to nine g's. Regular people get sick at around three to four g's. Abbey prepared to throw up.

But almost as soon as the feeling started, it stopped. She no longer felt motion sick, or even like they were moving very quickly. Yet she could see the clouds were still hurtling past at the same pace. They broke through the cloud cover a moment later, and the rate at which the fluffy ma.s.s of white sank beneath them was disconcerting at best. Their acceleration was definitely still more than five g's and they were shifting direction every few seconds-yet she couldn't feel any motion at all. Roller coasters were engineered to maximize velocity, acceleration, and rate of change in acceleration, otherwise known as jerk, within a range that still allowed the human body to antic.i.p.ate the upcoming changes and brace accordingly. But her body lurched and cringed in preparation for jolts that never came. If the derivatives of displacement didn't apply in this world, what laws of physics did?

Max's now-familiar voice came over the intercom again. "Okay, the motion stabilizers are on. You guys can go back to work."

"That was totally sweet," said Caleb, undoing his seatbelt and rushing over to the window.

Simon unbelted himself and joined his brother.

When she could see that her brothers weren't careening into walls or floating in the air, Abbey followed suit. "This is crazy," she said, shaking her head.

They watched in silence as the clouds slipped farther away. They started to pa.s.s what looked like satellites, docking stations, and other vessels. Then the air started to get darker, and they could see the glimmer of stars, like they were on the edge of the atmosphere and s.p.a.ce was just above them.

"You know," Simon said, "I bet a computer like this would have a self-diagnostic system. At least...if I were to develop an advanced program, I would include one." He turned to the computer wall and spoke. "Computer, run self-diagnostic!"

Nothing occurred.

"Calling the computer 'Sarah' seemed to work last time," Abbey ventured, even though she wasn't sure why she was even partic.i.p.ating in this crazy exploit.

"Okay, Sarah, run self-diagnostic," Simon ordered once again. This time the computer hummed to life. Lights flashed.

"In what system?" the voice asked politely.

"Um...navigation," Simon said uncertainly.

"Problem identified in line 3,845,934 of code," the computer responded.

"Er, um. Sarah, can you show that line on screen?" Simon said. One of the large screens flicked on, and rows and rows of characters appeared on it.

Abbey gazed at the screen willing her brain to make sense of the symbols, letters and numbers, all in no apparent pattern. "It all looks like Greek to me."

"Actually," Simon said, "it looks like an advanced derivation of current a.s.sembly codes."

"What's that?" Abbey asked.

"It's the language that the programmer language is compiled into after the programmers are finished with it, but before it's compiled into machine code," Simon said. "Um...Sarah, can you describe the problem exactly?"

"Calculations of x, y and z s.p.a.ce coordinates cannot be undertaken," the voice answered.

"Values must have been produced at one time. How long has this problem been occurring?" Simon asked.

"Nine days, four hours, twenty-three minutes and thirty-seven seconds."

"What happened at that point?" Simon asked.

"An upgrade was applied to the navigation system."

"I wonder if this is what it's talking about." Caleb's voice emerged from the other side of the room. He'd been rummaging through the storage bins. He walked across the room with a small blue and silver manual. Improve your s.p.a.ce coordinate calculations to an additional decimal place, it read in big bold letters. Smaller print below read: Calculate s.p.a.ce coordinates to the third decimal place to improve precision in landing and reduce time-consuming navigation into s.p.a.ce ports. On the bottom of the box, there was an emblem reading: S Systems.

Simon scanned the box. "I wonder if it's some sort of legacy problem," he said.

"A leg of what problem?" Abbey knew he had said 'legacy'. But she hated the superior tone he adopted when he engaged in computer talk. "Would you care to explain that to us non-computer techies?" Abbey asked.

Simon did not look up from the manual. "When an upgrade has been applied that's not backward compatible with the existing code." He flipped open the book and started reading. "The third in a series of upgrades improving s.p.a.ce-coordinate calculation precision decimal place by decimal place." Simon paused. "And the calculations cannot be completed..." he murmured almost to himself. He turned back to the computer. "Sarah, did this problem occur with the previous upgrades?"

"No previous upgrades have been applied to the navigation system."

"The previous upgrades must have made some changes to the code that were necessary for this upgrade to work," Simon said. He no longer looked at Abbey when he spoke. He was talking to himself, lost in his programming world.

Abbey wandered back to the window.

Caleb, having long since given up on a.s.sisting Simon, was looking out the window. "We seem to be descending," he said.

Max's voice came over the intercom again, informing them that they had arrived in Newellay, they should strap in, and they would only be stopping for a few minutes.

Abbey and Caleb watched out the window from their seats. The descent was smooth and uneventful. From what Abbey could see of the city, it was very similar to the one they'd left, except larger-low buildings around high-rise hubs, with train tracks extending out in several directions. This city was situated on what appeared to be an ocean, with crystal blue water extending as far away as the eye could see. A causeway, much like the one in their previous location, came into sight, except this one simply hung in the air above the city attached to a tall, rectangular tower that connected the causeway to the ground. Rows of identical causeways with moored vessels lined up next to each other, each attached to its own tower. A large sign on the closest tower read Gate 3. There was an empty docking point below the ship with a stack of metallic containers next to it. Abbey strained to make out the lettering on the side of the containers as their vessel descended into its spot. She could make out the letters 'AL' on one.

Once they were docked, the metallic white hull of another large vessel parked nearby limited their view.

Simon flipped through the lines of code on the screen.

Abbey sifted through the manuals and boxes that Caleb had deserted in favor of the window.

"Newellay. Where do you suppose that is?" she asked her brother.

"I dunno. The signs I can see from here are in English though," Caleb replied, craning his neck to see beyond the vessel next to them.

"Do you think we're still on Earth? Or a different planet, or world, or alternate reality?"

Caleb scratched his head. "Well, Max said 'Earth-to-Earth,' and the people seem to be human. The signs are in English and we haven't seen any strange beings or anything. I'm guessing Earth."

Abbey was about to reply when Simon turned to them, holding out the navigation upgrade box, his face pallid in the glow of the screen. "Look at the date," he said, "and the slogan."

Abbey grabbed the box and looked at the small print along the bottom.

2036.

S Systems You won't even know we're here.

Chapter 3.

Operating Systems.

Abbey looked at her brothers. Simon's blue eyes bored into her, but he said nothing. She hunched her shoulders.

"Way cool," said Caleb. "We're in the future."

"We don't know we're in the future," Abbey said. "We don't know anything. It could be a misprint. This could be a dream. We could be in 2036 in a different world. We don't know anything." She thought of her room with the pink and orange flowered wallpaper and bedspread; her desk with all its science equipment; Wallace, her brown guinea pig; Farley, whom she loved, despite his tendency toward general harebrainedness; and, of course, her mom and dad. She might never see any of it again. She bit back tears. "The important thing is that we get home."

Max's voice came over the intercom. "All done here, folks. Better strap yourselves back in for liftoff. How're the repairs going, anyway?"

Abbey held her breath, but Simon's voice crackled with authority. "Max, just checking. Did you install any previous upgrades to the nav system?"

"Well now, I dunno. I don't think so. I'm pretty busy for that kind of stuff. But then my buddy told me I could save a ton of points by improving the accuracy of the Earth-to-s.p.a.ce jumps, landing me right at the docking station and saving all that coasting energy. So, I decided to give it a try." The ship's humming intensified.

Simon was still strapped into the seat in front of the computer.

Abbey hustled over to her seat and glared at Caleb, who continued milling around the compartments.

"Right. So, no, then?" Simon asked. "You haven't installed any other upgrades?"

Abbey could almost see Max hanging his head. "No."

"You know you have to install them, right? Later upgrades won't always work if you don't install the earlier ones," Simon said.

"Sorry, mate. I didn't know. Can you fix it?"

"I'm not sure yet."

Caleb spoke up. "Max, I need to come up to the c.o.c.kpit for a little bit and take a look at the navigation system from up there. I'll head up your way after we take off."

"Sure thing. We're heading off now."

Abbey wanted to pinch Caleb's arm, but she was already strapped in. "What are you thinking, Cale? You can't go up there."

"Why not? He's not going to hurt me. And I need to figure out where we are."

"No, you don't," Abbey said. "How are you going to figure out where we are? Or when we are? You need to stay here with us. We need to get off this ship and go home." She could almost smell Wallace's soft fur. She had experiments to run and homework to do. Simon ignored her outburst, his eyes fixed on the lines of code on the screen.

Caleb affected his most earnest expression. "Abs, what if we have a problem getting back? I need to collect all the data I can. Consider this important data collection. You know how important data is."

Abbey frowned. "You just want to go to the c.o.c.kpit."

Caleb cracked a sheepish smile. "Okay. But you have to admit, more information is better. There could be tons of clues up there-maps, more manuals. And I can ask questions." The ship detached and began its upward glide. Caleb staggered across the floor in a drunken lurch.

"Aren't you going to sit down and put on your seat belt?"

"Nah, I'm going to hang on to this bar here. It wasn't too bad last time."

Simon turned and glared at Caleb. "Sit down and strap yourself in, you nimrod, or your head will slam against that wall and I'll have to deliver your brains home to Mom."

A body experiencing a force undergoes acceleration. Abbey almost giggled as Caleb decided to accelerate to his seat. The ship launched into the air again. She felt the blood drain from her face and her eyeb.a.l.l.s press into the back of their sockets.

When the ship was stable again, she returned to the computer screen. There was no pattern to the code that she could discern. Geometry and algebra had an intuitive arc she could follow. But the lines of code were irritatingly nonsensical.

Caleb sidled over to the screen, the skritch of his bamboo sandals the only sound in the room. "I'm heading to the c.o.c.kpit for a bit. Just to take a look around. Any questions I can ask while I'm up there to make me look like I know what I'm doing?"

"Not likely," Simon grunted.

Caleb was nonplussed. He rocked back in his sandals. "Very funny, big bro. Seriously, give me something. The more I figure out, the better off we all are."

"Fine. Confirm that the problem started immediately on the first jump after the upgrade, and that he's getting no results, not inaccurate results."

"Got it." The skritching sound moved across the room toward the door.

Abbey felt a wave of concern for Caleb. "Just don't ask any dumb questions," she said.

He wiggled his eyebrows. "Righto. No dumb questions. If I don't come back in fifteen minutes, come and get me." Abbey gasped, but Caleb winked. "I'm kidding, Abbey. I'll be back." The door swooshed closed.

"I think I might have figured it out. See this?" Simon pointed at a line of code.

Abbey squinted at the screen.

"It's set to be an integer. That's what the computer was expecting. Maybe that's how accurate they could be when they first started doing Earth-to-s.p.a.ce jumps."

Abbey could see the words on the screen reflected in her brother's eyes while he spoke.

"When the system upgrade was applied, it started calculating the coordinates with three decimal places, but the computer was still expecting an integer. I might just have to change this one line of code."

Abbey was taken aback. Could it be that simple? They could actually fix the problem and leave, without being clapped in irons and never seeing their home again?