She nudged open the front door with her toe and flounced out to greet them. The hem of her field hockey skirt, which she’d worn to the team’s end-of-the-year party this afternoon, fluttered in the breeze.

“You guys!” she crowed in the happiest voice she could muster.

Her friends looked up at her. For a moment, Ali was sure they knew everything. A split second later, though, they were all smiling as though nothing was amiss. Maybe they really didn’t know something was amiss. Emily perked up visibly, the other day’s transgressions seemingly forgotten—at least for now. Spencer and Hanna, who had just arrived in the yard, too, came toward them, and the girls convened in a group hug. But as Ali clung tightly to her friends, she glanced over her shoulder just in time to see a curtain on the second floor of her house flutter. It was the guest room. A figure stood at the window, staring at them.

“Your barn,” she said to Spencer, breaking away and steering them through the hedges. She needed to get off this property, fast.

Blessedly, the girls followed behind her like good little sheep. But her sister’s face haunted her as the five of them moaned about how long the school year had been. And when she heard someone calling “Hey, Alison! Hey, Spencer!” her stomach seized. It sounded, for a moment, like her sister’s voice.

She turned around and saw Mona Vanderwaal and her band of geeks coming toward them. Part of her wanted to throw her arms around Mona in relief. Instead, she blurted, “Not it!”

“Not it,” her friends said milliseconds after.

Mona rolled up on her scooter. Chassey Bledsoe and Phi Templeton followed behind, Chassey on a mountain bike, Phi on foot with her trusty, ridiculous yo-yo.

“You guys want to come over and watch Fear Factor?” Mona asked.

“Sorry,” Ali simpered, dredging up the appropriate level of nastiness. “We’re kind of busy.”

Then she whipped around and trotted off. Her friends followed. When she rolled her eyes, they rolled theirs, too. They don’t know, she thought, her heartbeat slowing down. They don’t suspect anything. But then she peeked toward her house again. The light was still on in the guest room, and that face was still at the window. To Ali’s horror, Hanna was squinting at the window, too.

Ali yanked her arm. “C’mon,” she said.

They walked the line between Ali’s backyard and Spencer’s. A huge, garishly yellow bulldozer was parked at the back next to a cone-shaped pile of dirt. “I’m so happy the workers aren’t here right now,” Ali said loudly, making sure everyone’s attention was on her—and not on the window.

Emily stiffened. “Are they saying stuff to you again?”

“Easy, there, Killer,” Ali joked, and the girls giggled. She glanced over her shoulder once more. The light in the window was off now. The face was gone. But was her sister going to sit idly by in her room all night like a good little girl? It seemed impossible.

The barn was just ahead. Ali led the others toward it, praying that her sister wasn’t watching from the kitchen to see where they were going. What if their mother took her eyes off her? What if she got out?

Giggles sounded from inside the barn. “I said, stop it!” a voice squealed. It was definitely Melissa.

Spencer stopped short. “Oh God. What is she doing here?”

Ali looked at Spencer sharply. “I thought you said your sister was in Prague.”

“I did.” Spencer flung the door open to reveal Melissa and Ian lounging on the couch, several bottles of beer between them. Melissa shot up and adjusted her headband. Ian’s eyes canvassed the girls, his smile lazy and beguiling.

“Were you spying on us?” Ian teased.

Spencer looked horrified. “It’s just . . . I didn’t mean to barge in. . . . We’re supposed to have this place tonight.”

Ian playfully hit Spencer’s arm. “I was just messing with you.”

A spark seemed to pass between them, which, in turn, sent a rush of possessiveness through Ali’s body. “Wow,” she said loudly. “You two make the kuh-yoo-test couple. Don’t you agree, Spence?”

Spencer blinked hard. Melissa gave Ali a strange look, then tugged on Ian’s shoulder. “Can I talk to you outside for a sec?”

Ian drained the last of his Corona and rose from the couch. “Adieu, ladies.”

He swept past Ali and shot her a covert smile. She nodded ever-so-slightly in return. They were on for meeting in her yard at 9PM. She knew he’d be there. All she had to do now was send a text to Melissa just before their kiss. And then Melissa would see everything.

After they were gone, Ali turned back to the girls. “Ian is so hot,” Hanna was saying. “Even hotter than Sean.” A tiny, conflicted look fluttered across her face. She was probably thinking about Josie and Sean at the party.

“You know what I think?” Ali said to Hanna, her nastiness oozing over. “Sean really likes girls who have good appetites.”

Hanna looked surprised. “Really?”

“No,” Ali blurted. The laugh that came out of her mouth was subconscious, but when she noticed the hurt look on Hanna’s face, she clamped her mouth shut. She felt crackly tonight, unbridled, totally out of control. She felt like she needed to be the most extreme Alison she could be, not only to show her sister, but to show her friends, too. No one can replace me. No one is better than I am. Don’t you dare suspect a thing.

Suddenly, she had an idea. Maybe there was a way to get her friends in her ultimate power for real. Even if they did see her sister again, they’d always side with Ali, doing whatever she wanted, which meant the two of them could never switch back. It might also be a way to erase what they’d seen for good.

“I know the perfect thing we can do,” she suggested. “I learned how to hypnotize people.”

Spencer looked worried. “Hypnotize?”

“Matt’s sister taught me,” Ali said, her excitement growing. This was perfect. She could hypnotize them and demand that they bow down to her and only her. She could also extract the memory of her sister in her bedroom from their minds. “Want to see if it works?” she asked, trying not to beg.

Everyone shifted uncomfortably. “I don’t know,” Aria murmured. “Doesn’t hypnosis make you say things you don’t want to say?”

Ali gritted her teeth. “Why?” she teased. “Is there something you don’t want to tell us?” She pointed at Pigtunia. “And why are you still carrying that everywhere? Didn’t your dad give it to you?”

Aria paled, and again, Ali felt a remorseful twinge. Perhaps it had been too mean. Hanna looked sharply at her, her brow furrowed, and Spencer paused, a bite of popcorn halfway to her mouth. Ali could tell they were all working through what Ali had said in their minds. Why was Aria upset? What had Ali said? What didn’t they know?

“Being hypnotized, um, does sound sort of sketch,” Spencer blurted.

“You don’t know anything about it,” Ali insisted urgently. “C’mon. I can do all of you at once.”

She watched as they shifted their weight. A long silence prevailed. Please, she repeated silently. Please, please, please.

“I’ll do it,” Hanna piped up.

“Me, too,” Emily said.

Spencer and Aria begrudgingly shrugged, too. Ali let out a huge mental sigh.

“Okay,” she said excitedly. “Everyone sit in a circle.” She rushed around the room, shut off the lights, and lit a few votive candles sitting on the coffee table. Then she took her place at the head of the room, shut her eyes, and let out an om-like hum that sounded vaguely spiritual.

Her friends closed their eyes, too, and Ali felt even better. Maybe hypnosis really was going to work. Maybe she would be able to say some words and they’d forget. “Okay, just relax,” she said. “I’m going to count backward from one hundred. As soon as I touch all of you, you’ll be in my power.”

Emily laughed shakily. “Spooky.”

Ali began to count, padding around the room and looking at the crowns of her friends’ heads. Her voice filled the space, the numbers dropping from ninety to sixty to forty-five. At thirty, she saw a flash at the window and turned. Something black disappeared from view. Her heart skipped a beat.

“Twenty-nine . . . ,” she said, moving toward the window. Then there was another flash. She shielded her face, spots forming in front of her eyes. When her vision cleared, a figure stood on the other side of the glass, a modern-day Polaroid camera at her side. Ali almost screamed.

It was her sister.

“Twenty-eight . . . ,” Ali said with only a slight hiccup, her mind scattering in a million directions. No. She would never, ever forgive her mother for letting her sister out. What should she do now? Run out of the barn, tell her parents Courtney was loose? But then her friends would open their eyes and see the two identical twins, one on the outside, one on the inside. They’d exchange knowing glances. See? Everything we suspected was right. And what if they liked her twin more?

Should she pretend nothing was wrong, then? That didn’t seem right, either. Her sister might barge inside the barn. She might tell the truth. And then what?

Ali glanced at her friends, but they were still sitting with their eyes closed. She twisted the window blinds shut, then pulled the curtains tight, then counted through the twenties, then through the teens. She pictured her sister crouched at the window, not seeing inside anymore, but still listening. She checked the door to make sure it was bolted tight. It was. But what if Courtney got in some other way?

“Ten, nine . . .” Swallowing a lump in her throat, Ali touched her friends’ foreheads. First Aria, then Hanna, then Emily. “Three . . . two . . . ,” she incanted.

Suddenly, Spencer’s eyes sprang open. To Ali’s horror, she leapt across the room and lunged for the window. Ali whipped around, her heart jumping into her throat. “What are you doing?”

“It’s too dark in here,” Spencer said, reaching for the dowel that would twist open the blinds. She opened them, and Ali winced. Her twin was gone, though.

“It’s got to be dark,” Ali demanded, rushing toward her. She had no idea if Courtney would reappear, but she wasn’t taking any chances. “That’s how it works.”

Spencer paused, her hand on the rod. “No, it doesn’t.”

“It does,” Ali growled, her heart beating fast. There was no way Spencer was opening that window. Her sister would be on the other side, like a perverse reflection in a mirror.

Spencer turned from the window and placed her hands on her hips. “It doesn’t always have to be the way you want it, you know.”

“Close them!” Ali roared, trying to control the desperation in her voice.

Spencer rolled her eyes. “God, take a pill.”

“You take a pill!”

Ali stared at her. Something suddenly hit her: What if Spencer knew? Maybe she’d figured it all out—she was the smartest of all of them. Maybe she’d even seen Courtney at the window just now and had put all the pieces together. She was messing with Ali because she could; she knew exactly what Ali was afraid of.