Switcheroo.

Once upon a time, there were two identical twin sisters, Alison and Courtney. They were alike in every way: Both had long, blond hair; huge, clear, round blue eyes; heart-shaped faces; and winning smiles that melted hearts. When they were six, they rose matching purple bikes up and down their family's driveway in Stamford, Connecticut, singing "Frere Jacques" in a round. When they were seven, they climbed up the big-kid board together and held hands the whole way. Even though their parents gave each of them her own bedroom with her own canopied princess bed, they were often found sleeping on the same twin mattress, their bodies entwined. Everyone said they shared that indescribable twin connection. They made promises to be best friends forever.

But promises are broken every day.

In second grade, things started to change. They were little things at first—a dirty look, a slight shove an indignant sigh. Then Courtney showed up in Ali's Saturday art class insisting she was Ali. Courtney sat at Ali's desk in school on a day her sister was sick. Courtney introduced herself as Ali to the UPS man, the new neighbors with the puppy, and the old lady at the pharmacy counter. Maybe she pretended she was her sister because Ali had a little extra sparkle, a certain something that got her noticed. Maybe Courtney was jealous. Or maybe Courtney was forced. Ali made me do it, Courtney told her parents when she was caught. She said if I didn't pretend to be her for the day, something awful would happen to me and you and all of us. But when their mom and dad asked Ali if this was true, her eyes grew wide. I would never say something like that, she answered innocently. I love my sister, and I love you guys.

Suddenly, Courtney and Ali were getting into screaming matches on the playground. Then Courtney shut Ali into a bathroom stall at lunchtime and didn't let her out. Teachers called the girls' parents, their children close when they passed Courtney, worried she might hurt them, too. The final straw came that flawless spring day when the girls' parents found Courtney sitting on top of her sister, her hands around Ali's throat. Doctors were called. Psychiatric evaluations were performed on both girls. Ali handled it with poise, but Courtney panicked. She started it, she insisted. She threatens me. She wants me gone.

Paranoid schizophrenic, the doctors said in grave tones. That sort of thing could be treatable, but only with a lot of care. It was up to Ali to make the final decision, though—and, tearfully, she decided that her sister should go. And so a facility was found. Off Courtney went, away from her family, away from everything she knew. Her parents reassured her that they would bring her home as soon as she was better, but weeks passed, then months. Suddenly, Courtney was sort of...forgotten.

Sometimes, a family is like an ear of summer corn: It might look perfect on the outside, but when you peel the husk away, every kernel is rotten. With the DiLaurentises, the girl who seemed like the victim might just have been the tormentor. Sending Courtney away might just have been Ali's master plan. And maybe, just maybe, all Courtney wanted was what she deserved—a happy life.

This is Rosewood, and after all—and these are Rosewood's most mysterious twins. And as you know, in Rosewood, nothing is ever as it seems.

The first thing Courtney DiLaurentis heard when she woke up the morning her life changed was the ticking of the clock on the wall. It was telling her, in a not-so-subtle way, that time was running out.

She looked around the unfamiliar bedroom. Her parents had moved from Stamford, Connecticut, a few years ago to avoid the shame of putting a daughter in a mental institution. They'd relocated to Rosewood, Pennsylvania, a filthy-rich suburb about twenty miles from Philadelphia where even the dogs wore Chanel collars. Because they knew no one when they moved, they didn't have to tell anyone about their crazy daughter in the hospital. They'd even changed their last name from Day-DiLaurentis to simply DiLaurentis in hopes that it would keep nosy neighbors from Connecticut away.

The guest room Courtney was staying in smelled like mothballs and had a twin bed with an old plaid comforter, a wicker dresser too shabby for even a mental ward's day room, and a small, chipped bookshelf containing dated cooking magazines and a bunch of boxes marked Taxes and Statements. The closet was filled with Christmas decorations, pilled afghans her grandmother had crocheted, and ugly sweaters she couldn't imagine anyone wearing. In other words, the room was a repository for everything her family wanted to forget about—Courtney included.

Courtney pushed the covers back and walked into the hall. The house, a huge Victorian, was designed in such a way that the upstairs overlooked a great room, giving Courtney a bird's-eye view into the kitchen. Her older brother, Jason, was hunched over the table with a bowl of Frosted Flakes. Her twin sister, Ali, flittered around the counter. Her hair was a perfect blond wave spilling down her back, and her pink T-shirt gave her clear skin a healthy glow. She lifted a pile of newspaper and looked under it. Then she opened a silverware drawer and slammed it shut.

"Alison, what's the matter?" asked Mrs. DiLaurentis, who wore a gray Diane von Furstenberg wrap dress and heels. It looked like she was going to a job interview instead of taking her daughter to a new mental hospital.

"I can't find my ring," Ali snapped, opening the trash bin and peering inside.

"What ring?"

"My initial ring, duh." Ali opened another cabinet and slammed it hard. "It's the one I wear, like, every day." She whipped around and faced her brother. "Did you take it?"

"Why would I take it?" Jason answered between bites.

"Well, I can't find it," Ali snapped. "Just like I can't find my piece of the flag," she said, giving Jason a pointed look.

Jason wiped his mouth with a napkin. "Even if I did know about your stupid piece of the flag, anyone is legally allowed to take it—even the people who helped hide it. The stealing clause, remember?"

"Maybe you took it to give it to someone else." Her gaze drifted to the second floor.

Courtney stepped away from the railing. Back in the bedroom, she opened the flowered suitcase she'd had since third grade and studied its contents. Inside was a T-shirt almost the same shade of pink as the one Ali was wearing. She found dark indigo jeans that matched Ali's, too. She slipped them on.

Time Capsule was a long-standing tradition at Rosewood Day, the private school Ali and Jason attended, and finding a piece of the torn-up flag was a rarity for a sixth grader. All weekend, Ali had been boasting about the Time Capsule scrap she'd found—although technically, Jason had told Ali where the piece was, which didn't seem fair. Ali had decorated her piece at the kitchen table after dinner two nights ago, giving Courtney, who was watching TV in the den, superior looks. Low how important I am, those looks said. You're not even allowed to leave the house.

But Ali hadn't had that look on her face when her flag went missing yesterday. In the privacy of her pathetic little guest room, Courtney had run her fingers over the silken fabric and Ali's puffy silver drawings—a Chanel logo, a Louis Vuitton design, a cluster of stars and comets. Courtney had drawn a little wishing well in the corner, just wanting to make her mark on something her sister coveted so much. Then I'll give it back, she promised herself. But Jason had gotten to it first. He'd seen Courtney looking at it in her room and rushed in, saying, "Do you really want things worse between you guys?" Then he'd snatched it back before she could say a word.

Courtney was about to shut the suitcase when her gaze drifted to the pamphlet tucked into the suitcase's pocket. The Preserve at Addison-Stevens, the front said. There was a photo of a bouquet of irises beneath the title. They were the same sorts of flowers her parents had gotten for her grandmother's funeral.

She opened the booklet and stared at the first page. We assist children and adolescents in developing effective coping skills and building self-esteem to be able to return home and back to school, it read.

Tears sprang to Courtney's eyes. She'd been in hospital care since she was nine—three whole years. And even though she'd gotten used to the Radley the same way a mouse might get used to living in a cage, she'd been horrible things she never wanted to witness again. Ever since the hospital announced it was closing its door and converting into a luxury hotel, Courtney had assumed her family would bring her back to Rosewood to live with them. When her father had driven her here on Friday, he'd said as much—this would be a trial visit that would perhaps turn into something more permanent.

But for some reason, circumstances had changed in the last twenty-four hours. Mrs. DiLaurentis had knocked on Courtney's door last night and told her to pack her things at once, slipping the pamphlet for the Preserve into her hands. "We think this will be the best thing for you," she cooed, stroking her daughter's hair.

Courtney leafed through the pamphlet's pages, staring at the photos of the patients. They had to be models—they looked too happy. She'd heard terrible things about the Preserve from other kids who had gone there. People called it "death row" because so many kids committed suicide while inside. Others called it "Rapunzel's tower" because parents left their kids in there for years. No Internet, television, or phone calls were allowed. The nurses were like extras from One Flew Over the Cuckoo's Nest, and the doctors on staff had no qualms about tying kids to their beds to keep them calm. Parents loved t, though, because the place looked beautiful from the outside. And it was super expensive—it had to be good, right?

But she wasn't going. She'd been formulating a plan all night to figure out how. Now all the pieces were fitting into place...except for the opportunity she needed. She hoped one would arise—and soon. Her parents were taking her away in forty-five minutes.

She buried the pamphlet under her packed clothes and wheeled the suitcase to the top of the stairs. Then she walked down the stairs. Something caught her eye out the back window. Four girls were standing behind the bushes, whispering. They looked about Courtney's age, and she could hear their voices through the screen.

One girl, a blonde in a field hockey skirt and a white T-shirt, placed her hands on her hips. "I was here first. That flag's mine."

"I was here before you," a second girl spouted. She was a little on the chubby side and had frizzy brown hair. "I saw you come out of your house only a few minutes ago."

A third girl stomped a purple suede boot. "You just got here, too. I was here before both of you."

Courtney ran her tongue over her teeth. Were they here for Ali's flag? And they'd made a reference to one girl coming from next door—that had to be Spencer Hastings. Mrs. DiLaurentis had mentioned her name at dinner on Friday, and Mr. DiLaurentis had made a sour face. He'd said Spencer's were such show-offs, building a third addition to their house, converting that perfectly good barn into a luxury apartment for their oldest daughter. As if a bedroom isn't good enough? he'd railed.

"Do you see them out there?" Courtney asked Ali, who was now standing at a counter, angrily whipping through a magazine, headphones in her ears. Jason was gone, and by the sounds of it, their parents were still upstairs, getting dressed.

Ali's head snapped up. She tore the headphones out. "Huh?"

"There are some girls outside. One of them is the girl who lives next door."

"She's in the yard?" Ali looked annoyed and walked to the window. But when she peered out, she frowned. "I don't see Spencer. Thank God."

"You're not friends with her?"

Ali snorted. "No. She's a bitch."

And you're not? Courtney thought.

Ali turned to face her as if Courtney had said it out loud. A nasty smile settled across her lips. "Cute shirt. But it's giving me deja vu."

Courtney grabbed a banana from the basket. "I liked the color."

"Yeah, right." Ali sauntered to the counter and grabbed a donut from the open box.

"Careful," Courtney said, strolling toward her. "Donuts will make you fat."

Jelly dripped down Ali's chin. "So will mental hospital good, schizo."

Courtney winced. She wasn't a schizo, and Ali knew t. "Don't."

"Don't," Ali imitated, her features turning ugly.

Courtney sucked in her stomach. Ali always used a nasal, dumbed-down voice to mimic her. "Stop it," she snapped.

"Stop it," Ali imitated.

Courtney felt the old fire rise up inside, the one that had gotten her in trouble before. Although she tried her hardest to suppress it, something broke loose. "Guess what," she spat. "I do have your Time Capsule flag."

Ali's eyes widened. "I knew it. Give it back."

"It's gone," Courtney said. "I gave it to Jason. And he doesn't want to give it back to you." It wasn't exactly the truth, but this version sounded better.

Ali glowered at Jason, who had just appeared in the doorway. "Is this true? You knew she had my flag?"

Jason looked back and forth between the girls, his gaze lingering on their matching outfits. "Well, yeah, Ali, but—"

Ali's gaze darted to something in Jason's pocket. The shiny blue fabric peeked out. She snatched it out halfway, her eyes widening at the wishing well that was now wedged between the manga frog and the bubble-letter awesome. Her eyes narrowed on Courtney. "Did you draw this?"

Jason grabbed it back from her and stuffed it back in his pocket. "Ali, just let it go."

Ali squared her shoulders. "You're always on her side!"

"I'm not on anyone's side," Jason said.

"Yes, you are!" Ali glowered at Courtney. "It's a good thing I told mom that you threatened me last night. That's why you're going to the Preserve, you know."

Courtney's eyes widened. "I didn't do anything to you!"

Ali tipped her chin down. "Maybe you did. Maybe you didn't. Either way, you're not welcome here, bitch."

"Ali, enough!" Jason shouted.

"Enough!" Ali imitated with a sneer. When she brushed past him for the stairs, she shoved him. Jason staggered backward and crashed into a wrought-iron bookshelf. The whole thing wobbled, and a platter with the New York City skyline on the top shelf shook precariously. Jason lunged forward, but it was too late. The plate shattered on the floor.

The silence after the crash was deafening. Jason glared at Courtney, who had frozen in the corner. "Why did you have to start things with her?" he hissed.

"I couldn't help it," Courtney said weakly.

"Yes, you could," Jason said. And then, letting out a frustrated groan, he pushed out the back door.

Courtney's insides turned out. "Jason, wait!" she yelled, running to the window. Jason was her only ally—she couldn't have him angry at her. But when she gazed out the glass, Jason was gone. The four girls were still cowering in the bushes, though.

She glanced over her shoulder into the kitchen. Pieces of the New York City plate lay all over the floor. Soon enough, her mother would appear from whatever she was and discover the mess. She would call to her two daughters to ask what had happened. One would appear from upstairs. What if the other daughter was outside, talking to a few girls from school? It wouldn't be Courtney out there, after all—she didn't know anyone. She wasn't even allowed outside.

This was it. Her opportunity. If she went out there, their parents would think she was Ali, not Courtney. It would be the first time she'd ever impersonated her sister without Ali making her. The first thing you need to do, she told herself, is channel her. No one will believe you're here if you don't. So she shut her eyes and channeled her sister. A beautiful bitch. A manipulative queen bee. The girl who'd ruined her life.

Her skin prickled. It wasn't even that difficult: Courtney had been the queen bee of a group of popular girls at the Radley, scoring the best table in the day room, controlling what shows they watched on TV, putting on the best performance for the ward's talent show. And even before she'd gone to the Radley, kids had loved her—more than her sister, in fact. People felt at ease with Courtney; they picked her for kickball, they teamed up with her for art projects, she got more valentines than anyone else in the class. Ali, however, sometimes puts people off. She was too pushy, too intense. She yelled at people when no adults were watching, pouted when she didn't get the best gift in the Secret Santa exchange, and once even kicked a girl's brand-new kitten that she'd brought to show-and-tell. Yes, Ali was beautiful—a teensy bit more beautiful than Courtney, in fact—but she wasn't the most-loved. It was why she'd worked so hard to get Courtney out of the picture. She wanted to be the one and only star.

Courtney noticed Ali's blue wedged sitting by the door and slipped them on. To ensure her mother would see exactly where she was—and where her sister wasn't—she casually knocked another plate off the shelf. As it fell with a loud, hard-to-ignore crash, Courtney pushed the screen door open and watched as the girls, who were now arguing loudly, fell silent and looked up. By the intimidated, reverent expressions on their faces, she knew she already had them fooled. Of course they thought she was Ali.

"You can come out," she yelled in the most confident voice she could muster.

The girls didn't move.

"Seriously, I know someone's there," she said. "But if you've come for my flag, it's gone. Someone already stole it."

Spencer emerged from the bushes first. The others followed. And then it just...happened. They assumed she was Ali, and they asked her questions. Answers spilled from Courtney's mouth so naturally, like this was a role that was perfect for her. And when Mrs. DiLaurentis appeared on the porch, her gaze flickered cautiously at the girls in the yard—these definitely weren't Ali's friends. But when she looked at her daughter, she didn't suspect a thing. She just assumed Courtney was Ali. And when she closed the door again, the family was in the car within minutes. They drove away. Just like that.

Courtney was so excited and nervous and scared that she could barely keep up her apathetic act with the girls in the yard. She felt like she was about to burst. She felt like giving every tree n the yard a huge hug.

By the time Courtney returned to the house, she felt like she'd just run the distance to the Radley and back. Her head felt light. Her limbs felt heavy. She looked around the kitchen. Pieces of the plates were still on the floor. A flower vase has been knocked over, too. The quiet house seemed to reverberate with the phantom sounds and voices of what had just transpired. Violent, desperate screams echoing in the air. A scuffle to get into the car. A protest that they had the wrong twin.

She walked through the silent rooms, her sister's wedges clomping on the floor. Her plan had worked. But suddenly, panic struck her. Now she had to keep it up. This wasn't something that might only last a few days or weeks before people caught on that the wrong girl was at the Preserve. She had to figure out a way to stay home forever.

She ran upstairs to her sister's bedroom, taking the stairs two at a time. Her gaze scanned Ali's black-and-white bedspread, the cutout magazine ads and pictures of her friends on the walls, the bulging closet full of clothes. She darted to Ali's bed and slid her hand under the mattress. Ali's diary was buried precisely in the middle, just as it had been yesterday. She sat down, opened to where she'd left off, and read.

But when she got to the end, the fizzy feeling in her stomach had intensified. The diary was all about Naomi Zeigler and Riley Wolfe, and it made a lot of shadowy references to secrets and inside jokes that Courtney would have no way of knowing. There was no way she could remain friends with Naomi and Riley—she'd have to ditch them and form a new clique. Only, who?

The four girls in the yard popped into her head. Spencer, Aria, Emily, and that last girl, the chubby one. She ran to Ali's fifth-grade yearbook and scoured the pages. Hanna—that was her name. They hadn't sighed her yearbook—none of them knew Ali well. Perfect.

Slam.

Her head whipped up, and she shoved the diary back under the mattress. Only an hour had passed. Had they returned? Had they figured it out?

She peeked out the front window. There was a black car chugging at the curb; she couldn't see the driver. Footsteps sounded across the kitchen floor, then creaked on the stairs. She remained stock-still as whoever it was padded down the hall. A figure appeared in her doorway, and she almost screamed.

Jason looked at her with narrowed eyes. "Did they already take her?"

Courtney nodded, still not daring to breathe.

Jason's mouth became small and tight. "Well, I guess you're happy now, huh, Ali?"

He shook his head and continued toward his room. The door slammed loudly, rattling the walls. A few seconds later, the opening bars of an Elliott Smith song blared.

Courtney ran her hands down the length of her face. He'd called her Ali.

She walked to the mirror. The girl in the glass wore a deep-pink and wedge heels. She had glossy hair, a heart-shaped face, and an impish smile. After a moment, she threw back her head and tossed her hair over her shoulder, just the way Ali did, and the gasped. She'd nailed it.

Euphoria washed over her like a tidal wave. She was going to rule the school. Become fabulous. Turn into the best Alison DiLaurentis possible. She deserved it, damn it. And her sister? She thought of Ali's face as her parents shoved her into the car, the life she would lead in the Preserve. But what was done. And it was only fair.

She stood up straighter, admiring the girl in the mirror. Suddenly, she remembered something, ran back into the guest room, opened the top drawer of the ugly bureau, and pulled out the silver ring she'd stolen last night when Ali had taken it off to wash the dishes. She pulled it out and held it to the lamp. A small A was engraved into the face. Smiling to herself, she slid the ring onto her right pointer finger, the same finger Ali wore it on.

Then she stared at the girl in the mirror again. "I'm Ali," she said to her reflection. "And I'm fabulous."