A Pair of Docks.

Jennifer Ellis.

The Derivatives of Displacement.

* Position is the 0th derivative of displacement.

Displacement indicates the change in position of a point, particle, or object. *

Chapter 1.

Coventry Hill.

Abbey added the last valence sh.e.l.l to her ionic bonding diagram of sodium chloride and paused to listen. Instead of the usual clack, clack, clack of Simon's computer keyboard, the clatter of containers of metallic objects being overturned and drawers being opened and closed echoed down the hallway.

Abbey moved on to covalent bonds.

Simon sauntered past her and down to the crypt-their joking name for the dark and uninviting bas.e.m.e.nt of the split-level rancher they shared with their parents and Abbey's twin, Caleb. The sound of storage bins being dragged across the floor drifted up the stairs. Simon returned to the kitchen and went to the fridge where he filled two water bottles and made four salami-and-lettuce sandwiches, wrapping each methodically in wax paper.

"What are you doing?" Abbey asked.

"Running away," Simon said.

"No, seriously."

"None of your business." His eyes, so blue they bordered on purple, met hers unflinchingly. Her heart skittered a little. He pulled his black toque over his head.

"I'm going out," he said. "To a friend's. Tell Mom I'll be home by eight."

"But..." Abbey started, the words you don't have any friends dying on her lips.

Simon lifted his chin slightly as if to challenge her, and then took his sandwiches and water bottles and descended the stairs. The bas.e.m.e.nt door slammed.

Abbey drew five valence electrons for nitrogen before placing her pencil against the top of her notebook. Simon never went out after school. She rose and went to the picture window in the living room. The speckled gray of the empty road curved away from their drive and descended into town. She crossed the living room to the window that looked out onto the base of Coventry Hill, the small wooded mountain area that ab.u.t.ted their home on the edge of the town, and saw Simon's black toque disappearing up the path into the afghan of green.

Abbey grabbed her new pink and orange American Eagle cardigan and slipped on her sneakers. She eyeballed Farley, their Chesapeake Bay Retriever, curled in a circle on his bed in the living room. Farley would probably eat Mrs. Forrester's fish fertilizer again. Best to leave him behind. Abbey paused on the doorstep. How long would this take, really? Not long, she hoped. But who knew when her parents would be home? She thrust her key into the lock, turned it, and headed across the street.

The back of Caleb's gray t-shirt, Levis, and blue and tan Adidas sneakers stuck out from underneath Mrs. Forrester's camellia bush. Mrs. Forrester's autistic adult son, Mark, waved wildly at Abbey from inside the house. Mark's stares gave her a riff of unease deep in her gut. She waved back and checked her watch. Four o'clock. Still time. She had to finish her Chem 12 lab before dinner.

"Cale?" she said.

Her twin's brilliant red head popped out from under the glossy green leaves. "Yes?"

"Simon packed a bunch of stuff, including food, and said he was going to a friend's. Then he took off up Coventry Hill."

"Our Simon? Simon Sinclair, who never leaves his computer lair, has gone hiking?"

"We'd better go after him."

"What? We're going to stalk our older brother? What if he's on a date?"

"There's something wrong, Cale. He packed too much stuff and I saw Russell Andrews pushing him around again today. He looked even worse than usual. I'm worried."

Caleb c.o.c.ked his head to the side and shrugged, his quintessential gesture. He shrugged at everything, whereas Abbey stomped. She wondered if it was some weird yin and yang of body parts that developed in utero. For every action, there is an equal and opposite reaction. The girls at school thought Caleb was a laid-back surfer kind of dude, which apparently they found wildly attractive, and Caleb played up the persona. They probably thought he was dumb, but Abbey knew his shrugs meant he was thinking. He always liked to consider the situation, and looking like a silent jock bought him time. "I'm going after him," Abbey continued, "and I need you to come with me."

Caleb lowered his shoulders and nodded, placing his clippers next to the bin of garden waste. "Don't you think we should text Mom instead? I'm on the clock."

"Mom's way too busy. The election is in two weeks. Besides, what are we going to say? Simon went out for a hike? She would think that was lovely or some stupid thing."

Abbey turned and marched to the edge of the cul-de-sac that led to the hill. Mark banged the window with his fist as they left, yelling something at them. This was not an infrequent occurrence. Mark yelled a lot. It was frightening to see a large man with dark stubble and hunched shoulders throw his body around like that. There was a lot of ma.s.s there. Momentum equals ma.s.s times velocity, Abbey whispered in her mind-her stupid brainiac mind-feed, as her brothers called it-always running. She tried not to imagine Mark hurtling through the window. Acceleration due to gravity equals nine point eight meters per second squared. Abbey shivered slightly in the fall air.

"What's up with Mark today?" she asked, thumbing her hand at the window. "He's even more agitated than usual."

Caleb just shrugged.

Abbey started up the path, her legs already feeling fatigued. Perhaps she ought to stop skipping P.E. to go to the chemistry lab. Caleb fell into an easy step beside her. She peered through the dense foliage. The intertwining greens of tree and bush made her eyes cross.

"I heard Russell telling Simon outside homeroom this morning that he better not let him down. Russell looked really mad. Something's up."

Caleb's fingers closed around Abbey's arm while she spoke, and he pulled her into the bushes, the freckled finger of his other hand extended.

A few hundred meters away, Simon was crawling around on the forest floor in front of a rosebush dotted with pink flowers, groping at something on the ground like a blind person. And as if this weren't enough, there was a frantic urgency to his movements that alarmed Abbey.

"What is he doing? Is he hurt? We should go help him," Abbey hissed.

Caleb didn't move, and maintained his grip on her arm.

Abbey turned and glared at him, trying to wrench away. What if Simon had taken drugs or something and was sick? She couldn't imagine him doing that, but she knew other kids at school did. What if Simon had finally capitulated? She tried to push Caleb's hand away, but he outweighed her by about forty pounds. Unlike Simon, who remained reed-thin, Caleb had already started working out at the gym. She swatted at him. Then he went strangely bug-eyed, let go of her arm, and lurched to his feet.

Abbey spun around.

Simon was gone.

Caleb launched up the hill. Abbey chased after her twin, searching the trees for her older brother.

"Where did he go?" Abbey asked, her voice tight and wan with the exertion.

"He just vanished."

"That's impossible. He must have wandered off somewhere." She faced into the trees and called out a defiant, "Simon! Si! It's us. It's Abbey and Caleb." Her words came out as a tinny wail.

Caleb tugged at her arm again, his normally dancing green eyes deadly earnest. "Ab, I'm not kidding you. He was there one second, and then he was gone."

Bile rose into her throat. People did not just disappear. It was theoretically impossible.

"Look!" Caleb said, as they skidded to a stop where they'd last seen Simon. He pointed at the base of the flowered bush. Square stones embedded in the ground poked out from under the th.o.r.n.y bramble, their browns and grays blending into the dirt. Caleb raked his hands through his hair and lifted his shoulders in his customary shrug. "I dunno. This rosebush isn't wild. I heard this area was an old town site at the turn of the century when they were mining up here. Maybe there's an old foundation or well hidden underneath here... Maybe he fell."

"How could he have fallen through that bush? It's ma.s.sive," Abbey said. The bush towered overhead and spanned at least twelve feet in diameter-four meters, she corrected in her mind, in keeping with her resolution to use only metric like true scientists-its spiny branches reaching toward them in a wild spray of thorns. An unusual tree with a shiny green trunk and red, papery bark grew up out of the center of the bush.

"I'm going to crawl under that lower vine and take a look."

"What if you fall too?"

"I'll keep my hands on solid ground at all times and inch forward. No chance of me falling." Caleb sank to his knees and began to crawl forward. "Si? Simon? Are you there?" Caleb ducked his head under the rose vine and tried to look further into the green ma.s.s.

Abbey strained her eyes at the th.o.r.n.y bramble, listening for any response from Simon.

Then Caleb disappeared.

Abbey lunged forward, screaming, as she clutched for Caleb, but he vanished-not as if falling into a hole, but as if every last atom in his body had been annihilated by anti-matter, with no resultant burst of energy. There was simply nothing left.

"Caleb!" Abbey shouted, as she stood alone, while the trees whispered above her. But n.o.body answered. She began to shiver violently. This defied all definitions of reality that she'd constructed around her in her fourteen years of life. Her fingers brushed the cool gloss of her cell phone. If she called her mother and then waited, it might be too late.

Abbey crouched in front of the stones and reached her hand out, placing her forefinger on the center stone. The effect was instantaneous. She heard a slight whooshing noise and felt like she was on an elevator moving forward, instead of up or down. The forest became hazy. Wherever Simon and Caleb were, they were not in a well. Everything around her extended and blurred, as if she were being propelled at the speed of light. Light, which moves at three hundred thousand kilometers per second. She closed her eyes and tried not to scream.

Within a few seconds, the ground beneath her reconst.i.tuted and she decelerated. She had the feeling of being pushed off an escalator, and then she found herself blinking in suddenly dazzling sunlight. She scanned frantically for Caleb and Simon and nearly leapt on top of Caleb when she spotted him a few meters away. But then she just stared. She stood on some sort of causeway or marina dock suspended in the air over a scoured red clay hillside, a waist-high guardrail with metal siding the only thing between her and a significant drop. Smaller causeways branched off the main one on which she stood, and broad, small-winged planes or s.p.a.ce vessels hung in the air at various points along the branches, with gangplanks attached at the entrances to each. The berths all had different four-digit numbers, like addresses. The largest branching path, to the right off the main causeway, had a sign that read Commercial Only, while the two smaller branches extending off the left side of the causeway were labeled Recreational and Corporate.

Right behind her, two carved wooden platforms with benches sat on either side of a short, curving trail of stones. Abbey stared at the stones. What had just happened? Some sort of trick of quantum entanglement transport straight out of Star Trek? A catapult that could propel them through the air at the speed of light? Or had they not really left at all? She searched the hill for signs of the seams, the junction points, where this world faded into hers, an illusion that would fall away if she could just find the edges. But she could see no rift, just vast blue sky and barren hills dotted with spa.r.s.e scrub. To her right sat a small cubical building covered in mirrored gla.s.s set into the hill of red dirt. Below the causeway, the hill gave way to flatter, more vegetated land dotted with small, round dwelling-like structures. Many were half underground, with strange cone-like metal roofs, making them look like cl.u.s.ters of mushrooms. A small river snaked through the structures.

All the explanations Abbey could think of were highly improbable, and of far more immediate concern was the sinking realization that she couldn't see Simon anywhere. Her stomach had lodged somewhere near her lungs and tw.a.n.ged uncomfortably. Just the twitching of the sympathetic nerve in her stomach wall, she knew. But that didn't make it any better.

Two vessels cruised past overhead and sank gracefully into spots along the causeway, their physics of movement breathtakingly inexplicable. People could be seen loading and unloading vessels or walking up or down the causeway wheeling luggage. Railway tracks extended out from the building and ran directly down the side of the hill on a steep angle. A train raced up the hill on the tracks, another startling impossibility of physics-unless it was on a cable, like an elevator. Rail tracks emerged from the center of each cl.u.s.ter of structures below, like spokes on a bike.

It was hotter and windier than the warm October afternoon they had just left. Abbey squinted as the light refracted off buildings and surfaces with more force than it ever had in the world they'd left behind. But the sky was still blue, the signs were written in English, and the people moving around on various parts of the causeway appeared to be human.

She grasped Caleb's arm fiercely. He'd been gazing about just as wildly as she had. "We have to find Simon."

"He's over there," Caleb said, gesturing to the right. "Just sitting on that bench. I saw him when I came through."

Abbey saw what she'd missed before-the lone hunched figure of her brother on a distant bench on the main artery of the commercial causeway. "What are we going to do?"

"I guess we should go get Simon and then go home," Caleb said a bit reluctantly. She could already see an unnerving twitch of excitement brewing in his eyes.

"If we can even get home," Abbey said. "I don't think we should leave the stones." Her voice sounded slightly hysterical. Sympathetic nerves and limbic systems weren't useful in crisis situations, and Caleb, clearly, was in possession of neither.

"The stones are there," Caleb said. "I'll step back through and make sure we can go back and forth. Then we can go get Simon." Caleb's pupils had shrunk to specks of black in a sea of green ochre. "You have to admit, Ab, this is pretty cool-like going to Narnia or something!"

"Are you a mental case?" Abbey snapped. "This is so not cool. We might not ever get back or see our parents or Farley, or anything, ever again. What if you step on the stones and go somewhere else altogether?" She felt tears pooling in the corners of her eyes, and cursed the testosterone and general boy-ness of her twin that had led Caleb to jump off cliffs, climb trees, take jumps on his bike, explore alleyways, and propel them both into unwanted adventures all her life. This was an adventure of wholly new proportions.

"Okay, okay," Caleb said, holding up his hand. "I'll stick my head through to make sure we can go back. You hold my hand tightly. If I get pulled somewhere, you'll come with me."

"That could be even worse," Abbey said. "Then we won't even be with Simon."

"Do you have a better suggestion?"

"No. I don't know." She felt like she was on the verge of a full-blown panic attack as her mind efficiently, mechanically, and relentlessly calculated odds, risks, and probabilities.

The doors to the building opened. A man and woman stepped out and headed briskly in Abbey and Caleb's direction. The couple wore navy pantsuits, dark gla.s.ses, and sunhats with broad brims. ID cards hung around their necks.

Caleb pulled Abbey over to look over the guardrail with him. The comfort of his hand in hers steadied her a bit.

The woman spoke into a headset. "We'll handle the coordinate problem after we upgrade the OS for Warkentin." Abbey felt the slight swish of air at their pa.s.sing. The pair turned and headed down the corporate branch of the causeway. They were definitely human, they looked completely normal, and they spoke English. Abbey's mind flicked through the possibilities-a parallel universe, another planet, another world, or another time. All potentially fraught with dangers.

Caleb pulled her in the direction of the stones. "Let's just give it a try."

Abbey nodded. Her normally reliable brain, fully entrenched in fight-or-flight mode, was not generating any better suggestions.

Simon still sat on the bench four hundred meters away.

Abbey clenched Caleb's hand tightly in her own and braced herself on the causeway. Caleb leaned forward and edged one foot onto one of the stones, jutting his head out. Immediately, Abbey felt the pull from his body and then the acceleration. She tried to yank back on Caleb but her feet lost all traction, and then they were back in the forest, their forest, their eyes trying to adjust to the diminished light.

"See, it's fine," Caleb said. "We can just go back and forth."

"We don't know that," Abbey said, but she grasped this small shred of relief and held onto it tightly. "Let's just go get Simon."

Despite the unsettling but now familiar plummet through nothingness, the stones returned them to the causeway without incident. Simon had risen from the bench and his black toque bobbed slowly down the commercial causeway. They walked quickly after him, but he stopped every few meters to stare at something in his hands, making it easy to gain on him. What could he be doing? Despite her stress level, Abbey had to gape at the vessels that floated silently past, picking up speed as they moved farther away from the causeway, veering and rolling effortlessly. She looked for exhaust, for any sign of combustion, any hint of the type of fuel they used, but there was none.

Caleb's face shone with a barely suppressed look of rapture. He'd unb.u.t.toned his shirt, revealing his beaded peace necklace.

"Don't start enjoying this, Cale. We're getting Simon and then we're leaving," Abbey said, tying her sweater around her waist.

Simon whirled and jumped as they approached, and then stopped walking. His lips twisted into a smirky half-smile, but something almost like relief flitted across his pale face. He thrust his iPhone back into his jeans pocket. "Ah, the Squeaksters." He laughed almost manically at his personal joke regarding their supposed squeaky-clean status. He'd become more and more secretive and p.r.i.c.kly toward them in the last few months. Their mother had said to leave him alone when Abbey wept hot tears about it. That he was just going through teenage stuff. That he should be left to his programming, his increasingly all-encompa.s.sing obsession. But Abbey missed the patient and reserved older brother who used to play board games with her, who would hang back with her in social situations while Caleb always plunged ahead. She supposed that chumming with your geeky younger sister, who'd been afflicted with an exceedingly uncool IQ of over one sixty-five, wasn't high on the list of favorite activities for an almost sixteen-year-old boy. She was sure Simon was just as smart as she was. He was just better at hiding it.

"All done with your homework?" Simon had intended this to be sarcastic, Abbey was sure. But his voice broke a bit, and ended up sounding more scared than mean. He'd grown impossibly tall over the summer, and if he stopped wearing that toque and frowning all the time, might even be vaguely good-looking. Abbey couldn't believe none of the girls at Coventry High had noticed. But his averted eyes, eternal awkwardness, and preference for wearing all black likely screamed a warning to most females.

"Simon, where are we?" Caleb asked.

Simon pressed his lips together. "I'm not sure exactly."

"You better spill, or we'll tell Mom and Dad. How did you find this place?" Caleb said.

"Like they'd believe you."

"They might, and besides, look around-we're your best and only allies right now and you might need us. So spill. How did you know about this place?"

Simon scowled and removed a crinkled piece of paper from his pocket and thrust it at Abbey. She smoothed it out and read: Envelope-to: