Gretchen McNeil: 3:59

2:20 P.M.

JOSIE CROUCHED BEHIND THE PHOTON LASER module and aligned it with the beam splitter at the other end of the lab table. “Once we build the vacuum dome,” she said, making a minor adjustment to the laser’s trajectory, “this should work.”

“Should?” Penelope said.

Josie glanced at her lab partner. “There’s a reason no one’s been able to prove the Penrose Interpretation.”

Penelope snorted. “Because it’s unprovable?”

“Thank you, Captain Obvious,” Josie said, with an arch of her brow. “Would you also like to tell me why the sky is blue and the Earth is round?”

“Ha-ha.” Penelope bumped Josie out of the way with her hip and took her place behind the laser. “I don’t know how you talked me into doing this as our science-fair entry. What if it doesn’t work? I’ll never get into Stanford if I fail AP Physics.”

“We’re not going to fail.” Josie looked around the room at the array of textbook experiments their classmates were working on: balloons and static electricity, wave pools, concave mirrors. Total amateur hour, whereas she and Penelope were tackling Penrose’s wave-collapse theory of quantum gravity. It was like bringing a major leaguer to a T-ball game. “Mr. Baines grades on a curve. We’ll be fine.”

“We’d better be.” Penelope moved around the table. For the bazillionth time, she began carefully measuring out the positions of the one hundred or so mirrors they’d use in the experiment, noting their exact locations in her spiral notebook. Her straight black hair swished back and forth in front of her face as she scribbled furiously. “Are you sure you’re not just doing this as an FU to your mom?”

Josie stiffened. “Of course not.”

Penelope didn’t look up. “I don’t know. Seems like trying to prove an almost impossible theory that’s in direct conflict with the hypothesis your mom’s spent her entire career exploring is kind of a slap in the face.”

It was, of course. Josie knew it. Penelope knew it. If Josie’s mom had bothered to initiate an actual conversation with her daughter in the last six months, she’d probably know it too. But Josie wasn’t about to admit that in fourth-period physics.

“I’m worried about the laser,” she said, changing the subject. “I’m not sure it’s strong enough.”

Penelope calmly looked up at Josie with her almond-shaped eyes. A grin crept across her face. “We could always borrow the experimental laser your mom has up at her lab.”

“No way,” Josie said.

“Oh, come on! It’s perfect.”

Josie held firm. “We cannot use the hundred-kilovolt X-ray free-electron prototype from my mom’s lab, okay? Get over it.”

Penelope wasn’t about to give up. “Maybe you could have your dad borrow it? For legitimate work purposes? And then if it just happened to end up in our demonstration the night of the science fair no one—”

“My dad moved out last weekend,” Josie interrupted in a clipped tone.

She hadn’t told anyone yet, except Nick, and only because he’d picked her up for a date ten minutes after Josie’s dad had broken the news that he’d rented an apartment in Landover.

“Oh,” Penelope said, her eyes wide. “Shit, I’m sorry.”

“It’s okay.” It wasn’t.

Penelope opened her mouth to say something, when the loudspeaker in the classroom crackled to life.

“Attention, students,” said the voice of the school secretary. “We have a special announcement . ”

“What now?” Penelope groaned.

“Quiet down, everyone,” Mr. Baines said. The murmur in the classroom dulled.

Josie checked her watch. A special announcement five minutes before the end of the school day? That was weird.

“Good afternoon, this is Principal Meyers. As some of you may have heard, another body was found in the woods west of Crain Highway this afternoon . ”

The classroom erupted into agitated whispers. “What?” Penelope squeaked. “Another one?”

“Like the previous incidents, the victim was killed sometime between the hours of ten o’clock in the evening and four o’clock in the morning, from an apparent animal attack . ”

Josie arched an eyebrow. “Animal attack? In Bowie, Maryland?”

“Shh!” Penelope hissed.

“Therefore, students are asked to refrain from visiting the Patuxent River Watershed or other surrounding uninhabited areas after dark until the animal or . . .”

Principal Meyers paused and cleared his throat with that kind of dry, forced cough a kid makes when they’re trying to convince Mom and Dad they’re too sick to go to school.

“Until the animal,” he continued, “or other perpetrator responsible for the attacks is apprehended.”

“Other perpetrator?” Josie said. “What the hell does that mean?”

But Principal Meyers offered no response to Josie’s question. The loudspeaker popped once, twice, and fell silent.

2:35 P.M.

THE END-OF-DAY BELL PEALED THROUGH THE classroom, jarring everyone into action.

“Don’t forget,” Mr. Baines shouted above the commotion of screeching chairs, backpack zippers, and the almost choral musicality of thirty cell phones all being powered on at once. “Final review of your projects tomorrow. Be prepared to defend your hypotheses.”

“How can I think about my science project after that?” Penelope clutched Josie’s backpack as they slowly filed out of the room. “Other perpetrator. See? I knew the police were covering up for a serial killer.”

Josie half turned around. “Who said anything about a serial killer?”

“Sixteen dead bodies in six months, their gruesome, dismembered, and half-eaten remains left in the woods in the dead of night?” Penelope almost sounded excited as she described the murder scenes. “Please, this is classic serial-killer territory.”

Josie laughed. “Okay, CSI.”

“Fine, don’t believe me.” Penelope trotted alongside her in the crowded hallway. “But it fits. The pattern, the escalation. And now we’ve had two murders in the last week alone.” She paused and dropped her voice. “I’m sure this animal-attack crap is just a cover-up so the population won’t panic and descend into martial law.”

Ah, that was the Penelope Josie had known for years. The lovable conspiracy theorist who spent most of her free time combing antigovernment blogs and with each passing day became increasingly convinced that Big Brother was watching her. “Pen, you’re blowing this way out of proportion.”

“No, I’m not,” Penelope said, sounding hurt. “I never blow anything out of proportion.”

Josie planted her hands on her hips. “Remember that time you were convinced your eighty-year-old neighbor was a spy for the Venezuelan government? Or what about when you almost electrocuted yourself trying to find the hidden listening devices the NSA had installed in the walls of your house?”

Penelope pursed her lips. “Still no proof I was wrong about either, thank you very much.”

“Hey!” a familiar voice called out through the postclass crush of bodies. Josie spun around and caught her breath as she spied the tall, black-haired figure of her boyfriend, Nick Fiorino, threading his way through the crowd.