Thirty: The Doppelganger.

The following day after school, Ali stood in front of a long table in the lobby and watched as kids gave their names to Mrs. Ulster, the art teacher who was also in change of the seventh-grade graduation."Yes, of course, Andrew," Mrs. Ulster said, searching through a box on the floor and unveiling a long white graduation gown and matching cap for Andrew Campbell, one of the class nerds. His cap had a special medal on it because he'd gotten all A's that year. So did Spencer's, Ali guessed.

"Thanks," Andrew gathered the gown and beret in his arms. When he passed Ali, he smiled hopefully, like they were friends. She snorted and turned away.

Ali had picked up her gown the other day, so it was already at home, but she'd just retrieved her seat assignment and the two tickets each family was allowed for the event. All around her, kids were chattering excitedly about the ceremony that night. Rebecca Culpepper stated she was going to wear high-heeled sandals under her gown. Jordyn Wellesley announced he was going to break-down his way to the podium. Chassey Bledsoe asked who their speaker was going to be, but Ali just rolled her eyes as she passed. "We don't have a speaker, loser," she teased. "That's only for seniors."

Chassey looked cowed, like she was supposed to have known that. But as Ali walked toward the parking lot, she felt a swirl of anger. She'd been excited to walk in graduation all year, and now that it was home, it all felt so tarnished. Today had been the first full day that Courtney was home, and Ali hadn't been able to still through her classes, fearful that her sister might burst into her classroom any minute, blurting out the truth.

A Jeep honked in the parking lot, and Ali looked up and waved. Cassie turned the ignition when Ali climbed in and pulled toward the exit. As they wound through the parking lots, she raised her eyes and pointed with her chin toward a couple climbing the hill toward the senior lot, dark gowns swinging from their hands. "I can't believe he hasn't broken up with her yet."

Ali cranked her neck. It was Ian and Melissa. They held hands, and when they approached Ian's SUV, he grabbed Melissa around the waist and gave her a big kiss on the neck, to which she squealed and twisted away.

"I can't believe it, either," she mumbled, feeling a surprised stab of jealousy. It wasn't fair that Ian's relationship was all well and good after he'd screwed up hers. She wanted to pay for it—and she thought she knew how. She pulled out her cell phone and hunted for Ian's number. Want that kiss? she typed in a text. Meet me Thursday night. My yard. Nine PM sharp.

There was a ping within thirty seconds. You got it, Ian wrote back. Ali tried to muster up a flare of excitement—after all, kissing a hot boy was kissing a hot boy. But she felt nothing.

At Ali's curb, Cassie leaned on the steering wheel. "Do you mind if I come in for a sec? I really, really have to pee."

"No!" Ali practically shouted.

Cassie drew back, giving Ali a strange look. "Um, we're having problems with the septic system," Ali blurted, realizing how insane she'd just sounded. "It really smells." She looked hard at the house. Had a curtain fluttered? Could Cassie tell her twin was in there, just be looking at the place?

Cassie made a sympathetic face, then said good-bye. Ali shot out of the car and darted toward the door, relieved when Cassie pulled away from the curb. But just as she was twisting the knob, she heard voices inside.

"I didn't mean anything by it," her sister wailed.

"You should know better!" her mother answered sternly.

Ali's skin prickled. What had happened? And then, suddenly she heard different voices, this time from the backyard. "Why would she be in trouble? someone whispered. "She didn't do anything wrong."

Ali drew away from the door. Was that...Emily?

"Not that we know of," another familiar voice said. Ali almost choked on her gum. Spencer.

Her mind swirled. She hadn't invited them over. What were they doing here? Had her sister invited them? Or—worse—her mother, wanting Ali to break the news.

They could not know. If they did, what if they slowly figured out the rest of it—that Ali wasn't who she said she was? Maybe they'd always secretly wondered about Ali abruptly taking them on as friends. Dropping Naomi and Riley without explanation. That time Ali had gotten lost in Rosewood Day at the beginning of sixth grade. Maybe it was all cataloged in their brains, little niggling puzzle pieces that didn't quite make up a whole picture. With the introduction of a twin, it would. And if her parents figured out, they'd send her to the Preserve to punish her.

She stood on the front porch, terrified to go around the side and face the music. Suddenly, there was a loud slam. Her mother's voice keened out from the patio. "I just want to make sure you have the dimensions right," she yelled toward the workers in the back.

Ali stepped off the porch and tiptoes into the side yard just as her mother barreled across the back toward the gazebo workers, who were sitting around, seemingly doing nothing. "I'm not paying you to loaf," Mrs. DiLaurentis snapped, hands on hips. "Can't this get done any faster?"

One of the workers raised one shoulder. "We're waiting for the concrete to dry."

"When is this hole going to be filled?" Ali's mother demanded. "Tomorrow?"

The same worker shook his head, his floppy hair bouncing. "Friend. That's the earliest we could get the truck."

Mrs. DiLaurentis rolled her eyes and continued to chastise them. Ali took another step closer, her friends coming into view. They were all there, sitting on the back patio. Looking nonplussed. Blessedly, Courtney wasn't with them. So maybe they didn't know.

She took a deep breath and climbed up the patio stairs.

"Uh...hi?" she said.

Spencer stood up. A big, nervous smile spread across Emily's face. Aria stared at Ali impassively, and Hanna squirmed in her seat. They looked guilty, and Ali's ears rushed to the surface once more.

"What did she bust you for?" Spencer demanded.

Ali cocked her head, not sure if she should answer.

"Are you getting in trouble without us?" Aria went on, her light, easy tone of voice forced. "And why did you change? That halter you had on was so cute."

Ali blinked hard. Halter. Her sister had worn a halter the day before. Perhaps she'd put it on this morning, too, as it was probably the cutest thing she owned.

Her knees went weak. They had seen her twin...maybe even talked to them, but it wasn't because of their mother. Where had she been? In this house? Outside?

But then it hit Ali. She bet she knew exactly where they'd seen her sister. Ali's room.

That bitch, she thought, fury rising in her body like mercury inside a thermometer. How dare she! Was this phase one of her master plan? Was she trying to pass herself as Ali and try to switch back? What was even worse was that her friends had believed that "Courtney" was Ali. If her sister could convince them, she could convince anyone.

Emily cleared her throat, bringing Ali back to herself. "Do you want us to...go?"

Ali shook her head quickly, realizing she had no idea what sorts of expressions had just crossed her face. "Of course I don't want you to go," she mustered, trying to regain control. "My mom was mad at me because I...I threw my clothes in with her delicate again." She rolled her eyes. "But don't worry girls—I'm not grounded or anything. Our sleepover extravaganza can proceed as planned!"

The girls looked relieved, though something still seemed to hang over them. For a moment, Ali worried if they were looking at her and realizing there was something Thursday night after graduation, so they would have the place to themselves.

"Sweet," Ali said loudly, hoping that Courtney, where she was, heard. She wasn't going to let her sister get in the way of her fun. Let her try to switch. it was never going to happen.

Suddenly, she noticed a flash of blue across the Hastingses' yard. Melissa was on her way to the barn, her gown swinging from a hanger in her hand. She'd already slung the school's valedictorian mantle over her shoulder. Show-off.

Suddenly, Ali had to make everyone see how powerful she was, how crushing she could be. She wasn't sure if it was for her friends' benefit, exactly...or for the girl watching from within the house.

Ali stood up. "Hey, Melissa!"

Melissa stopped and turned around. "Oh. Hey, guys."

"Excited to go to Prague?" Ali smiled sweetly. "Is Ian going?"

Spencer reached across the table and dug her nails into Ali's arm. "Ali."

"No, Melissa answered after a pause. "Ian's not."

"Oh!" Ali heard her own voice say. "Are you sure that's a good idea—leaving him alone? He might get another girlfriend!"

She gave Spencer a meaningful glance. "Alison. Stop it. Now."

But Ali couldn't stop.

"Spencer?" Aria asked. "What's going on?"

"Nothing," Spencer said quickly.

Ali watched as the other girls exchanged an uncertain look. But none of them said anything. Then, Melissa adjusted the mantle around her neck and strode toward the barn. She glanced long and hard at the hole in Ali's yard but said nothing.

Spencer glared at Ali after Melissa was gone, but Ali didn't reply. She barely got through the rest of the visit, when the girls left, she sprinted back into the house and made a beeline for the bedroom. Everything was in its place. Next she found her mother, who was standing at the sink, washing a few glasses.

"Did you let my friends in when I wasn't here?" she demanded.

Mrs. DiLaurentis wheeled around, looking guilty. "Honey, I thought you were home. But then I saw you pull up with your field hockey friend and realized my mistake."

Ali's body started to shake. "So they talked to her?"

"Well, yes. But then I grabbed her."

"Were they in my room?"

Mrs. DiLaurentis's gaze fell to her feet. "She's just curious. The therapist explained everything to us: She hasn't lived a normal life. We've deprived her of that. Think of yourself as a role model."

The words hurt: It was her they were really talking about, her they thought was still in the hospital, rotting away, becoming weirder and more feral by the day. "Where is she?" Ali said, her voice low and tense.

Mrs. DiLaurentis placed a warning hand on Ali's arm. "Honey, don't start a scene. I'm sure she didn't mean anything by it."

"Where. Is. She?" Ali's emotions felt like a kite whose string had gotten away from her. It was the same way she used to feel when her sister would push and push and push until she snapped. It was amazing how, after all this time, the feeling could just come back as urgent and fresh as the day she'd first felt it.

The dish towel went limp in Mrs. DiLaurentis's hands. "Look, we'll be more careful, okay? We'll keep her inside from now on, just until we're sure she's not backsliding. She'll be inside or graduation, your sleepover. Okay?"

"Do you promise?" Ali demanded. Mrs. DiLaurentis nodded almost fearfully.

But it wasn't enough. Ali turned and stormed up the steps, passing her bedroom once more. The guest room door was closed. She banged on it so hard that her knuckles ached. "Courtney?" she bellowed.

But the door didn't open. "Courtney!" Ali screeched.

"Alison, please," Mr. DiLaurentis said, standing at the foot of the stairs.

"Open the door!" Ali screamed. The bedsprings inside the room squeaked. A drawer slid open, then closed. And then, distinctly, she heard a high-pitched giggle. It kind of sounded like a witch's cackle and sent a shiver down her spine.

"I know what you're doing!" Ali said, pressing her cheek against the door. "You can't get away with this!"

She heard footsteps, and the door flung open. Her sister wearing the striped halter again, just as Ali feared. Her hair was in a high ponytail, her new Polaroid was on a strap around her neck, and she had a big smile on her face. She held Ali's gaze for so long that Ali began to feel nervous.

"Why not?" Courtney finally asked, her voice full of mirth. "You did."