Aria looked at the others. “What’s going on?”

“Do you think…?” Spencer whispered.

“What if Ali—” Hanna started.

“Guys.” A voice came from behind them. Ali stood in the great room doorway. Her arms were at her sides and her face was pale—paler than they’d ever seen it before.

“What happened?” everyone said at once.

Ali looked worried. “I don’t know. But it wasn’t my fault.”

The siren got closer and closer…until an ambulance wailed into the Cavanaugh driveway. Paramedics poured out and rushed to the tree house. The rope had been lowered down.

“What happened, Ali?” Spencer turned, heading out the door. “You’ve got to tell us what happened.”

Ali started after her. “Spence, no.”

Hanna and Aria looked at each other; they were too afraid to follow. Someone might see them.

Spencer crouched behind a bush and looked across the street. That was when she saw the ugly, jagged hole in Toby’s tree house window. She felt someone creeping up behind her. “It’s me,” Ali said.

“What—” Spencer started, but before she could finish, a paramedic began climbing back down the tree house, and he had someone in his arms. Was Toby hurt? Was he…dead?

All the girls, inside and out, craned to see. Their hearts began to beat faster. Then, for just a second, they stopped.

It wasn’t Toby. It was Jenna.

Several minutes later, Ali and Spencer came back inside. Ali told them all what happened with an almost-eerie calmness: the firework had gone through the window and hit Jenna. No one had seen her light it, so they were safe, as long as they all kept quiet. It was, after all, Toby’s firework. If the cops would blame anyone, it would be him.

All night, they cried and hugged and went in and out of sleep. Spencer was so shell-shocked, she spent hours curled in a ball, wordlessly flicking from E! to the Cartoon Network to Animal Planet. When they awoke the next day, the news was all over the neighborhood: someone had confessed.

Toby.

The girls thought it was a joke, but the local paper confirmed that Toby had admitted to playing with a lit firework in his tree house, accidentally sending one at his sister’s face…and the firework had blinded her. Ali read it out loud as they all gathered around her kitchen table, holding hands. They knew they should be relieved, except…they knew the truth.

The few days that Jenna was in the hospital, she was hysterical—and confused. Everyone asked her what had happened, but she didn’t seem to remember. She said she couldn’t recall anything that happened right before the accident, either. Doctors said it was probably post-traumatic stress.

Rosewood Day held a don’t-play-with-fireworks assembly in Jenna’s honor, followed by a benefit dance and a bake sale. The girls, especially Spencer, participated overzealously, although of course they pretended not to know anything about what had happened. If anyone asked, they said that Jenna was a sweet girl and one of their closest pals. A lot of girls who’d never spoken to Jenna were saying the exact same thing. As for Jenna, she never came back to Rosewood Day. She went to a special school for the blind in Philadelphia, and no one saw her after that night.

Bad things in Rosewood were all eventually gently nudged out of sight, and Toby was no exception. His parents homeschooled him for the remainder of the year. The summer passed, and the next school year Toby went to a reform school in Maine. He left unceremoniously one clear day in mid-August. His father drove him to the SEPTA station, where he took the train to the airport alone. The girls watched as his family tore down the tree house that afternoon. It was like they wanted to erase as much of Toby’s existence as possible.

Two days after Toby left, Ali’s parents took the girls on a camping trip to the Pocono Mountains. The five of them went white-water rafting and rock-climbing, and tanned on the banks of the lake. At night, when their conversation turned to Toby and Jenna—as it often did that summer—Ali reminded them that they could never, ever tell anyone. They’d all keep the secret forever…and it would bond their friendship into eternity. That night, when they zipped themselves into their five-girl tent, J. Crew cashmere hoodies up around their heads, Ali gave each of them a brightly colored string bracelet to symbolize the bond. She tied the bracelets on each of their wrists and told them to repeat after her: “I promise not to tell, until the day I die.”

They went around in a circle, Spencer to Hanna to Emily to Aria, saying exactly that. Ali tied on her bracelet last. “Until the day I die,” she whispered after making the knot, her hands clasped over her heart. Each of the girls squeezed hands. Despite the dreadfulness of the situation, they felt lucky to have each other.

The girls wore their bracelets through showers, spring break trips to D.C. and Colonial Williamsburg—or, in Spencer’s case, to Bermuda—through grubby hockey practices and messy bouts with the flu. Ali managed to keep her bracelet the cleanest of everyone’s, as if getting it dirty would cloud its purpose. Sometimes, they would touch their fingers to the bracelet and whisper, “Until the day I die,” to remind themselves of how close they all were. It became their code; they all knew what it meant. In fact, Ali said it less than a year later, the very last day of seventh grade, as the girls were starting their summer-kickoff sleepover. No one knew that in just a few short hours, Ali would disappear.

Or that it would be the day she died.

1

AND WE THOUGHT WE WERE FRIENDS

Spencer Hastings stood on the apple-green lawn of the Rosewood Abbey with her three ex–best friends, Hanna Marin, Aria Montgomery, and Emily Fields. The girls had stopped speaking more than three years ago, not long after Alison DiLaurentis mysteriously went missing, but they’d been brought back together today for Alison’s memorial service. Two days ago, construction workers had found Ali’s body under a concrete slab behind what used to be her house.

Spencer looked again at the text message she’d just received on her Sidekick.

I’m still here, bitches. And I know everything. —A

“Oh my God,” Hanna whispered. Her BlackBerry’s screen read the same thing. So did Aria’s Treo and Emily’s Nokia. Over the past week, each of them had gotten e-mails, texts, and IMs from someone who went by the initial A. The notes had mostly been about stuff from seventh grade, the year Ali went missing, but they’d also mentioned new secrets…stuff that was happening now.

Spencer thought A might have been Alison—that somehow she was back—except that was out of the question now, right? Ali’s body had decayed under the concrete. She’d been…dead…for a long, long time.

“Do you think this means…The Jenna Thing?” Aria whispered, running her hand over her angular jaw.

Spencer slid her phone back in her tweed Kate Spade bag. “We shouldn’t talk about this here. Someone might hear us.” She glanced nervously at the abbey’s steps, where Toby and Jenna Cavanaugh had stood just a moment before. Spencer hadn’t seen Toby since before Ali even went missing, and the last time she saw Jenna was the night of her accident, limp in the arms of the paramedic who’d carried her down.

“The swings?” Aria whispered, meaning the Rosewood Day Elementary playground. It was their old special meeting place.

“Perfect,” Spencer said, pushing through a crowd of mourners. “Meet you there.”

It was the late afternoon on a crystal-clear fall day. The air smelled like apples and wood smoke. A hot-air balloon floated overhead. It was a fitting day for a memorial service for one of the most beautiful girls in Rosewood.

I know everything.

Spencer shivered. It had to be a bluff. Whoever this A was, A couldn’t know everything. Not about The Jenna Thing…and certainly not about the secret only Spencer and Ali shared. The night of Jenna’s accident, Spencer had witnessed something that her friends hadn’t, but Ali had made her keep it a secret, even from Emily, Aria, and Hanna. Spencer had wanted to tell them, but when she couldn’t, she pushed it aside and pretended that it hadn’t happened.

But…it had.

That fresh, springy April night in sixth grade, just after Ali shot the firework into the tree house window, Spencer ran outside. The air smelled like burning hair. She saw the paramedics bringing Jenna down the tree house’s shaky rope ladder.

Ali was next to her. “Did you do that on purpose?” Spencer demanded, terrified.

“No!” Ali clutched Spencer’s arm. “It was—”

For years, Spencer had tried to block out what had come next: Toby Cavanaugh coming straight for them. His hair was matted to his head, and his goth-pale face was flushed. He walked right up to Ali.

“I saw you.” Toby was so angry he was shaking. He glanced toward his driveway, where a police car had pulled in. “I’m going to tell.”

Spencer gasped. The ambulance doors slammed shut and its sirens screamed away from the house. Ali was calm. “Yeah, but I saw you, Toby,” she said. “And if you tell, I’ll tell, too. Your parents.”

Toby took a step back. “No.”

“Yes,” Ali countered. Although she was only five-three, suddenly she seemed much taller. “You lit the firework. You hurt your sister.”

Spencer grabbed her arm. What was she doing? But Ali shook her off.

“Stepsister,” Toby mumbled, almost inaudibly. He glanced at his tree house and then toward the end of the street. Another police car slowly rolled up to the Cavanaugh house. “I’ll get you,” he growled to Ali. “You just wait.”

Then he disappeared.

Spencer grabbed Ali’s arm. “What are we going to do?”

“Nothing,” Ali said, almost lightly. “We’re fine.”

“Alison…” Spencer blinked in disbelief. “Didn’t you hear him? He said he saw what you did. He’s going to tell the police right now.”

“I don’t think so.” Ali smiled. “Not with what I’ve got on him.” And then she leaned over and whispered what she’d seen Toby do. It was something so disgusting Ali had forgotten she was holding the lit firework until it shot out of her hands and through the tree house window.

Ali made Spencer promise not to tell the others about any of it, and warned that if Spencer did tell them, she’d figure out a way for Spencer—and only Spencer—to take the heat. Terrified at what Ali might do, Spencer kept her mouth shut. She worried that Jenna might say something—surely Jenna remembered that Toby hadn’t done it—but Jenna had been confused and delirious…she’d said that night was a blank.

Then, a year later, Ali went missing.

The police questioned everyone, including Spencer, asking if there was anyone who wanted to hurt Ali. Toby, Spencer thought immediately. She couldn’t forget the moment when he’d said: I’ll get you. Except naming Toby meant telling the cops the truth about Jenna’s accident—that she was partially responsible. That she’d known the truth all this time and hadn’t told anyone. It also meant telling her friends the secret she’d been keeping for more than a year. So Spencer said nothing.