Ever wish you could go back in time and undo your mistakes? If only you hadn't drawn that clown face on the Bratz doll your best friend got her eighth birthday, she wouldn't have dropped you for the new girl from Boston. And back in ninth grade, you would never have skipped soccer practice to hit the beach if you'd known Coach would bench you for the rest of the season. If only you hadn't made those bad choices, maybe your ex-BFF would have given you that extra front-row ticket Marc Jacobs's fashion show. Or maybe you'd be playing goalie or the women's national soccer team by now, with a Nike modeling contract and a beach house in Nice. You could be jet-setting around the Mediterranean instead of sitting in geography class, trying to find it on a map.

In Rosewood, fantasies about reversing fate are as common as girls receiving Tiffany heart pendants for their thirteenth birthdays. And four former best friends would do anything to travel back in time and make things right. But what if they really could go back? Would they be able to keep their fifth best friend alive…or is her tragedy part of their destiny?

Sometimes the past holds more questions than answers. And in Rosewood, nothing is ever what it seems.

"She's going to be so psyched when I tell her," Spencer Hastings said to her best friends Hanna Marin, Emily Fields, and Aria Montgomery. She straightened her green eyelet T-shirt and pressed Alison DiLaurentis's doorbell.

"Why do you get to tell her?" Hanna asked as she hopped from the porch step to the sidewalk and back again. Ever since Alison, their fifth best friend, had told Hanna that only fidgety girls stayed then, Hanna had been making a lot of extra movements.

"Maybe we should all tell her at the same time," Aria suggested, scratching the temporary dragonfly tattoo she'd pasted on her collarbone.

"That would be fun." Emily pushed her blunt-cut reddish-blond hair behind her ears. "We could do a choreographed dance and say, 'Ta-da!' at the end."

"No way." Spencer squared her shoulders. "It's my barn—I get to tell her." She rang the DiLaurentis's doorbell again.

As they waited, the girls listened to the buzz of the landscapers pruning Spencer's hedges next door and the thwock-thwock of the Fairfield twins playing tennis on their backyard court two houses down. The air smelled like lilacs, mown grass, and Neutrogena sunscreen. It was typical idyllic Rosewood moment—everything about the town was pretty, and that included its sounds, smells, and inhabitants. The girls had lived in Rosewood nearly all their lives, and they felt lucky to be part of such a special place.

They loved Rosewood summers best of all. Tomorrow morning, after they completed their last seventh-grade final at Rosewood Day, the school they all attended, they would take part in the school's annual graduation-pin ceremony. One by one Principal Appleton would call each students name, from kindergarten through eleventh grade, and each student would receive a twenty-four-karat gold pin—the girls' was in the shape of a gardenia, the boys' a horseshoe. After that, they would be released for ten glorious weeks of tanning, cookouts, boating trips, and shopping excursions to Philly and New York. They couldn't wait.

But the graduation ceremony wasn't the true rite of passage for Ali, Aria, Spencer, Emily, and Hanna. Summer wouldn't really start for them until tomorrow night, at their end-of-seventh-grade slumber party. And the girls had a surprise for Ali that was going to make this summer's kickoff extra special.

When the DiLaurentis's front door was finally flung open, Mrs. DiLaurentis stood before them, wearing a short pale pink dress that showed off her long, muscular, tanned calves. "Hello, girls," she said coolly.

"Is Ali here?" Spencer asked.

"She's upstairs, I think." Mrs. DiLaurentis stepped out of the way. "Go on up."

Spencer led the group through the hall, her white pleated field hockey skirt swinging, her dirty-blond braid bouncing against the middle of her back. The girls loved Ali's house—it smelled like vanilla and fabric softener, just like Ali. Lush photographs of past DiLaurentis trips to Paris, Lisbon, and Lake Como lined the walls. There were plenty of photos of Ali and her brother, Jason, from grade school on. The girls especially loved Ali's second-grade school picture. Ali's vibrant pink cardigan made her whole face glow. Back then, Ali's family had lived in Connecticut, and Ali's old private school hadn't required her to wear stuffy blue blazers for yearbook pictures like Rosewood Day did. Even as an eight-year-old, Ali was irresistibly cute—she had clear blue eyes, a heart-shaped face, adorable dimples, and a naughty-yet-charming expression, which made it impossible to stay mad at her.

Spencer touched the bottom-right corner of their favorite photo, the one of the five of them camping in the Poconos the previous July. They were all standing next to giant canoe, drenched in murky lake water, grinning from ear to ear, as happy as five twelve-year-old best friends could be. Aria put her hand on top of Spencer's, Emily put her hand on top of Aria's, and Hanna piled her hand on last. They closed their eyes for a split second, hummed, and broke away. The girls had started that photo-touching habit when the picture first went up, a memento of their summer of best-friendship. They couldn't believe that Ali, the girl of Rosewood Day, had chosen the four of them as her inner circle. It was a little like being joined at the hip with an A-list celebrity.

But admitting that would be…well, lame. Especially now.

As they passed the living room, they noticed two graduation robes hanging on the knob of a French door. The white one was Ali's, and the more official-looking navy one was Jason's, who would be going on to Yale in the fall. The girls clasped their hands, excited to put on their own graduation gowns and berets, which Rosewood Day graduates had worn ever since the school had opened in 1897. Just then, they noticed a movement in the living room. Jason was sitting in the leather love seat, staring blankly at CNN.

"Heeyyy, Jason," Spencer called, waving. "Are you so psyched for tomorrow?"

Jason glanced at them. He was the hot boy version of Ali, with buttery blond hair and stunning blue eyes. He smirked and went back to the TV without saying a word.

"Oh-kaay," the girls all murmured in unison. Jason had his hilarious side—he was the one who had invented the "not it" game with his friends. The girls had borrowed and reinvented the game for their own uses, which mostly meant making fun of nerdier girls in their presence. But Jason definitely got into funks, too. Ali called them his Elliot Smith moods, after the morose singer-songwriter he liked. Only, Jason certainly didn't have any reason to be upset now—by this time tomorrow, he'd be on a plane to Costa Rica to teach adventure kayaking all summer. Boo-hoo.

"Whatever." Aria shrugged. The four girls turned and bounced up the stairs to Ali's room. As they reached the landing, they noticed that Ali's door was closed. Spencer frowned. Emily cocked her head. Inside the room, Ali let out a giggle.

Hanna gently pushed the door open. Ali had her back to them. Her hair was up in a high ponytail, and she'd tied her striped silk halter top in a perfect bow at her neck. She stared down at the open notebook in her lap, completely entranced.

Spencer cleared her throat, and Ali whirled around, startled. "Guys, hi!" she cried. "What's up?"

"Not much." Hanna pointed at the notebook in Ali's lap. "What's that?"

Ali closed the notebook fast. "Oh. Nothing."

The girls felt a presence behind them. Mrs. DiLaurentis pushed past, waltzing into Ali's bedroom. "We need to talk," she said to Ali, her voice clipped and taut.

"But, Mom…" Ali protested.

"Now."

The girls glanced at one another. That was Mrs. DiLaurentis's you're-in-trouble voice. They didn't hear it often.

Ali's mother faced the girls. "Why don't you girls wait on the deck?"

"It'll just take a second," Ali said quickly, shooting them an apologetic smile. "I'll be right down."

Hanna paused, confused. Spencer squinted, trying to see which notebook Ali was holding. Mrs. DiLaurentis raised an eyebrow. "C'mon, girls. Go."

The four of them swallowed hard and filed back down the stairs. Once on Ali's wraparound porch, they arranged themselves in their usual places around the family's enormous square patio table—Spencer at one end, and Aria, Emily, and Hanna at the sides. Ali would sit at the table's head, next to her father's deck-mounted stone birdbath. For a moment, the four girls watched as a couple of cardinals frolicked in the bath's cold, clear water. When a blue jay tried to join them, the cardinals squawked and quickly sent him away. Birds, it seemed, were just as cliquey as girls.

"That was weird upstairs," Aria whispered.

"Do you think Ali's in trouble?" Hanna whispered. "What if she's grounded and can't come to the sleepover?"

"Why would she by in trouble? She hadn't done anything wrong," whispered Emily, who always stuck up for Ali—the girls called her Killer, as in Ali's personal pit bull.

"Not that we know of," Spencer muttered under her breath.

Just then, Mrs. DiLaurentis burst out of the French patio doors and across the lawn. "I want to make sure you have the dimension right," she screamed to the workers who were perched lazily on an enormous bulldozer at the back of the property. The DiLaurentises were building a twenty-person gazebo for summer parties, and Ali had mentioned that her mom was being very type A about the whole process, even though they were only at the hole-digging stage. Mrs. DiLaurentis marched up to the workers and started chastising them. Her diamond wedding ring glinted in the sun as she waved her arms around frenetically. The girls exchanged glances—it looked like Ali's lecture hadn't taken very long.

"Guys?"

Ali stood at the edge of the porch. She had changed out of her halter into a faded navy blue Abercrombie tee. There was a baffled look on her face. "Uh…hi?"

Spencer stood up. "What did she bust you for?"

Ali blinked. Her eyes darted back and forth.

"Were you getting in trouble without us?" Aria cried, trying to make it sound like she was teasing. "And why'd you change? That halter you had on was so cute."

Ali still looked flustered…and kind of upset. Emily stood up halfway. "Do you want us to…go?" Her voice dripped with uncertainty. All the others looked at Ali nervously—was that what she wanted?

Ali twisted her blue string bracelet around her wrist three full rotations. She stepped onto the patio and sat down in her rightful seat. "Of course I don't want you to go. My mom was mad at me because I…I threw my hockey clothes in with her delicates again." She gave them a sheepish shrug and rolled her eyes.

Emily stuck out her bottom lip. A small beat went by. "She got mad at you for that?"

Ali raised her eyebrows. "You know my mom, Em. She's more anal that Spencer." She snickered.

Spencer faux-glared at Ali while Emily ran her thumb along one of the grooves in the teak patio table.

"But don't worry, girls, I'm not grounded or anything." Ali pressed her palms together. "Our sleepovers extravaganza can proceed as planned!"

The four of them sighed with relief, and the odd, uneasy mood began to evaporate. Only, each of them had a weird feeling Ali wasn't telling them everything—it certainly wouldn't be the first time. One minute, Ali would be their best friend, and the next, she'd drift away from them, making covert phone calls and sending secret texts. Weren't they supposed to share everything? The other girls had certainly shared enough of themselves—they'd slipped secret to Ali that no one, absolutely no one else, knew. And, of course, there was the big secret that they all shared about Jenna Cavanaugh—the one they'd sworn to take to the grave.

"Speaking of our sleepover extravaganza, I have huge news," Spencer said, breaking them out of their thoughts. "Guess where we're having it?"

"Where?" Ali leaned forward on her elbows, slowly morphing back into her old self.

"Melissa's barn!" Spencer cried. Melissa was Spencer's older sister, and Mr. and Mrs. Hastings had renovated the family's backyard barn and allowed Melissa to use it as her own personal pied-a-terre during her junior and senior years of high school. Spencer would get the same privilege, once she as old enough.

"Sweet!" Ali whooped. "How?"

"She's flying out to Prague tomorrow night after graduation," Spencer answered. "My parents said we could use it, so long as we clean it up before she gets back."

"Nice." Ali leaned back and laced her hands together. Suddenly, her eyes focused on something a bit to the left of the workers. Melissa herself was traipsing through the Hastingses' bordering yard, her posture rigid and proper. Her white graduation gown swung from a hanger in her hand, and she'd slung the school's royal blue valedictorian mantle over shoulders.

Spencer let out a groan. "She's being so obnoxious about the whole valedictorian thing," she whispered. "She even told me I should feel grateful that Andrew Campbell will probably be valedictorian instead of me when we're all seniors—the honor is 'such a huge responsibility.'" Spencer and her sister hated each other, and Spencer had a new story about Melissa's bitchiness nearly every day.

Ali stood up. "Hey! Melissa!" She started waving.

Melissa stopped and turned around. "Oh. Hey, guys." She smiled cautiously.

"Excited to go to Prague?" Ali singsonged, giving Melissa her brightest smile.

Melissa tilted her head slightly. "Of course."

"Is Ian going?" Ian was Melissa's gorgeous boyfriend. Just thinking about him made the girls swoon.

Melissa shaded her eyes in the harsh sunlight. The royal blue mantle flapped in the wind. "No. He's not."

"Oh!" Ali simpered. "Are you sure that's a good idea—leaving him alone for two weeks? He might get another girlfriend!"

"Alison," Spencer said through her teeth. "Stop it. Now."

"Spencer?" Emily whispered. "What's going on?"

"Nothing," Spencer said quickly. Aria, Emily, and Hanna looked at one another again. This had been happening lately—Ali would say something, one of them would freak out, and the rest of them would have no clue what was going on.

But this clearly wasn't nothing. Melissa straightened the mantle around her neck, squared her shoulders, and turned. She looked long and hard at the giant hole at the edge of the DiLaurentises' yard, then walked into the barn, slamming the door behind her so hard that it made the twig-braided wreath on the back of the door thump up and down.

"Something's certainly up her butt," Ali said. "I was just kidding, after all." Spencer made a little whimpering noise at the back of her throat, and Ali started giggling. She had faint smile on her face. It was the same smile Ali gave them whenever she dangled a secret over one of their heads, taunting that she could tell the others if she wanted to.

"Anyway, who cares?" Ali gazed at each of them, her eyes bright. "You know what, girls?" She drummed her fingers excitedly on the table. "I think this is going to be the Summer of Ali. The Summer of All of Us. I can just feel it. Can't you?"

A stunned moment passed. It seemed like a humid cloud hung above them, fogging up their thoughts. But slowly, the clouds faded and an idea formed in each of their minds. Maybe Ali was right. This could be the best summer of their lives. They could turn their friendship around and make it as strong as it had been last summer. They could forget all the scary, scandalous things that had happened and just start over.

"I can feel it, too," Hanna said loudly.

"Definitely," Aria and Emily said at the same time.

"Sure," Spencer said softly.

They all grabbed hands and squeezed hard.

It rained that night, a hard, pounding rain that made puddles in driveway, watered gardens, and created little mini pools pm top of the Hastingses' swimming pool cover. When the rain stopped in the middle of the night, Aria, Emily, Spencer, and Hanna awakened and sat up in bed at almost the exact same moment. A foreboding feeling had settled over each of them. They didn't know if it was from something they'd just dreamed about, or excitement about the next day. Or maybe it was due to something else entirely…something far deeper.

They each looked out their windows onto Rosewood's tranquil, empty streets. The clouds had shifted and all the stars had come out. The pavement shone from the rain. Hanna stared at her driveway—only her mother's car was there now. Her father had moved out. Emily looked at backyard and the forest beyond it. She'd never braved those woods—she'd heard ghosts lived in them. Aria listened to the sounds emanating from her parents' bedroom, wondering if they'd woken up, too—or perhaps they were fighting again and hadn't fallen asleep yet. Spencer gazed at the DiLaurentises' back porch, then across their yard to the huge hole the workers had dug for the gazebo's foundation. The rain had turned some of the dug-up dirt to mud. Spencer thought about all the things in her life that made her angry. Then she thought about all the things in her life she wanted to have—and all the things she wanted to change.

Spencer reached under her bed, found her red flashlight, and shone it into Ali's window. One flash, two flash, three flashes. This was her secret code to Ali that she wanted to sneak out and talk in person. She thought she saw Ali's blond head sitting up in bed, too, but Ali didn't flash back.

All four of them fell back onto their pillows, telling themselves that the feeling was nothing and they needed their sleep. In twenty-four short hours, they'd be at the end of their seventh-grade sleepover, the first night of summer. The summer that would change everything.

How right they were.