"Smart girl." Tony continued to pace aimlessly behind the table, his shadow eating the light as he moved from point to point.

"But why can't we catch one?" Nick asked. "If they can attack us, kill us, feed on us, why can't we do the same to them?"

Tony laughed. "Who says we can't catch one?"

"But I thought . . . ," Nick started.

"That's what the government wants you to believe. The last thing they need is heavily armed lynch mobs tracking incredibly dangerous prey. They have government hit squads that are barely able to accomplish that. It would be a bloodbath if your average neighborhood watch tried to take matters into their own hands."

"Why is it so difficult to catch them?" Josie asked.

"They exist in a complex quantum state, without a fixed superposition," Tony said. "And they can shift between universes at will." He turned to Josie. "I think that's when when you can see them, in the instant that they phase shift, like they're cycling through the dimension you belong to."

"Wow," Josie said. "That blows the rules of quantum properties out of the water."

Nick shook his head. "I don't understand."

"They're like me," Tony said simply. "I mean, I'm here and I'm not. You can feel me and hear me and smell me when I choose to shift my mass into this universe. But as you can tell, I'm not quite of this world anymore. And not of any other. I'm something in between, the glue that's holding the pages of the book together."

"So the Nox are the same?" Nick asked, rubbing the circulation back into his wrists.

"Yes," Tony said. "They can shift their mass at will between our world and their own. And they've adapted to it relatively quickly, just like they adapted to a penchant for humans as dinner."

"The space in the portal," Josie said. She thought of the darkness that seemed to engulf her, the weight of an entire universe trying to squeeze the life out of her. She tugged on Nick's hand. "Remember when you were checking out the portal that day you tried to kill me?"

Nick flinched. "I wasn't going to kill you."

"Whatever. But remember the inky blackness that oozed all around you when the portal started to close?"

"Exactly," Tony said. "That's exactly what I am."

"What you are?" Josie asked. The viability of Tony's experimental antidote being a way home was quickly diminishing.

"I am the stuff of the portal now."

"How?"

"My first attempt at an injectable was an inoculation, designed for humans. Like the eventual formula, it was deuterium-rich, and the idea was to phase-shift humans ever so slightly so we could coexist in the same universe with the Nox without them even knowing we were there.

"The problem was that it was too dangerous to attempt a phase shift. I even injected myself with the antidote last year, in the hopes I could get the green light to attempt the experiment on myself, but I was shut down."

"I had no idea," Nick said. He sounded hurt.

"Sorry, Nicky. Sharing my work around the dinner table would violate about a half dozen nondisclosure agreements. We had a few Nox in captivity to experiment on-again, not dinner-table conversation-and I'd spent a year adjusting the formula to use it on them instead of us."

"Amazing," Josie said.

"We had injected two Nox, and Dr. Byrne was attempting to create a micro black hole to suck them beyond the event horizon before it collapsed on itself."

"So what happened?" Nick asked.

"The explosion. I was in the other room, testing the controls that would raise and lower the blast glass to expose the Nox to the beam. Dr. Byrne was in the main chamber, finishing the last calibrations. We hadn't even started the process when a blinding flash tore through the room. I'd never experienced anything so intense. It actually threw me to the ground."

"I remember," Josie mumbled.

"When I came to, your mom was sprawled on the floor and the Nox were gone."

"So that's how they got into your world," Nick said. "Two Nox, already breeding. That's not good."

Tony whistled. "No, not good at all." He shook his head. "Anyway, I helped who I thought was Dr. Byrne get to her feet and realized something was wrong. Her lab coat. Her hair. Her shoes. Physically she looked exactly like Dr. Byrne, but it wasn't her."

"My mom."

Tony sighed. "She was disoriented, confused. The lab was different, and then she saw me." He paused. "I didn't know yet what had happened to me, how the explosion had reacted with the antidote in my system. She completely freaked out."

Nick placed his hand gently on Josie's shoulder. "Your poor mom."

"I could hear boots pounding down the hallway outside the lab. I only had a few seconds to make a decision. I'm sorry I had to abandon her. I didn't know what else to do. I had to find out who wanted us dead, and I figured the best way to do that was to actually be dead."

"Because someone sabotaged the experiment?" Josie asked.

"Exactly. The security and medical teams arrived within moments of the blast. Once I realized what had happened to me, I literally disappeared into the shadows of the room and waited. The blast had knocked out the security cameras, so once they removed your mom from the lab, I had a few seconds to examine the blast radius. The laser itself exploded, not the deuterium."

"So anyone could have tampered with the laser," Nick said.

"In theory, yes."

"Even Dr. Byrne." Josie recalled the conversation she'd overheard in one of Jo's dreams. Jo's mom seemed anxious to get her hands on the vial that contained the antidote. Desperate, even.

"It makes the most sense," Nick said with a glance at Josie. "She could have had access to the equipment, and we know for a fact there was an insider willing to sabotage the experiment and sell your formula at a massive price tag."

"I suppose," Tony said. He sounded unconvinced. "But Dr. Byrne was a scientist. She was just as invested in the outcome of the experiment as Dr. Cho and I."

Josie's eyebrows shot up. "Dr. Cho?"

"Yes, she worked on my team."

Josie was on her feet in an instant. "Nick, Dr. Cho is the one 'treating' my mom at Old St. Mary's. I assumed she was a psychiatrist or something."

"Geneticist," Tony corrected. "She specialized in mapping the genetic code from the unstable tissue samples we'd managed to retrieve from the Nox."

"What are the odds it's the same Dr. Cho?" Nick asked.

"High." Tony began pacing again.

Nick turned to Josie. "What would she want with your mom?"

Tony walked faster this time, his dark silhouette a metronome's pulse between the two walls of the shed. "The antidote. They'd want the formula for the antidote."

"But Dr. Byrne didn't develop it," Nick said.

"Yes, but she was the last one with it. There were two vials of it on her desk when we began the experiment. After the explosion, only one."

"It passed through the portal," Josie said. "With Dr. Byrne."

Tony caught his breath. "How do you know?"

Nick pulled the vial out of his pocket and handed it to Tony. "Because it passed back through."

"Amazing," Tony said.

"Yeah," Josie added. "And Dr. Byrne is desperate to get it back."

"With two breeding Nox, a swarm large enough to threaten the human existence could exist in just a few years." Tony handed the vial back to Nick. "There, as here, whoever controls the antidote would be very powerful. That's why I've been trying to re-create it here, in secret. I figured that way, no single government entity would have control over it. I'm only missing a powerful enough laser to make a real test. If it works, it would be enough to kill for."

Something clicked in Josie's brain. "Enough to kill for? Enough to send a swarm of Nox to attack?"

Tony stared at her, the faceless black giving no hint of emotion. "Yes, absolutely."

"They were sent after us?" Nick asked.

"Like I said, it was a coordinated attack," Tony said. "The generator was disabled. Someone knew where you would be and when."

Nick touched the back of his head and winced. "But how could they . . ." His voice trailed off and he turned suddenly to Josie.

She came to the same realization at the same time. The three of them were supposed to meet at the warehouse that night: Nick, Josie, and Penelope. "If they came after us, then they'll go after Penelope too."

Nick sprang to his feet. "Then let's get there first."

FORTY-SIX.

10:15 P.M.

THE ONE GOOD THING ABOUT HAVING A POPULATION terrified to go out at night was that there was no traffic after the sun went down. Not that there would have been an abundance of joyriders out for a late-night drive in Josie's version of Bowie, Maryland, but in this world, there weren't even cops on the street. No all-night gas stations, no twenty-four-seven convenience stores with their bright red-and-green neon signs warming the night sky. Nothing. Even the streetlights were dimmed in areas with a low density of houses, or perhaps just areas that weren't as affluent. Money was power. Literally.

Nick raced through the suburban landscape, blasting through stop signs and blackened traffic lights. He hit a drainage ditch and the SUV jumped with such violence Josie's head smacked the roof. But she didn't say a word. She wished he could make the car go faster.

If anything happened to Penelope, it would be all Josie's fault.

Nick screeched to a halt in front of a large, well-lit tract home just a few miles south of town.

"Lights are on," Josie said. "Good sign." She started to open the door.

Nick laid a hand on her knee. "Maybe you should stay here."

"Why?"

Nick didn't even blink. "Just in case."

Josie jerked her leg away from his hand. "If something happened to her, it's my fault. I got her into this mess."

"This isn't all on you," Nick said firmly.

Josie looked away. She couldn't help thinking of her own friend Penelope back home. How, in the end, Penelope had been the only one there for her. This Penelope had done almost the same thing, and how did Josie repay her? By making her a target in a very dangerous game.

"Come on." Nick reached across Josie and unlatched the passenger door. He practically lay on her lap as he pushed the heavy door open just an inch, and held it there. The wound on the back of his neck-the price of his own role in helping Josie-was still red and swollen from the makeshift stitches. "Hurry up," he grunted. "Can't hold it all night."

Josie kicked the door open with her foot. "Thanks."

"Don't mention it." Nick sat up straight, wincing as he tossed his hair out of his face. "Let's go find her."

Everything seemed normal at Penelope's house. All the lights were on, including the one over the front porch. Nick rang the doorbell and waited. After a few seconds he tried again. They could hear the soft melody of the bell echoing through the house, but no one answered the door.

He tried the handle in case it was unlocked. No luck. "Come on," he said, grabbing Josie's hand. "Let's check the back."

Light streamed out of the kitchen and dining-room windows that faced the back of the house, and Nick and Josie had no difficulty staying in the bright swath of safety they provided. Josie could see dirty dishes in the sink-cleared from dinner, no doubt. But no one was home.

"Try her cell," Josie suggested.

Nick had called her a dozen times on the way over, but no one had picked up. "You think it'll be any different now?"

"If she's inside, we might hear it."

"Good point." Nick pulled his phone out of his jeans pocket and hit redial.

They stood still, ears straining against the deafening silence.

"Listen!" Nick heard it first. The harsh electronic ring of Penelope's phone. He turned to his right. "Over here."

He followed the ringtone around the corner of the house to the garage. The light from the windows ended there, and Nick and Josie had to backtrack around to the front of the house. He dialed again, and this time they could clearly hear the phone ringing from inside the garage.

"Maybe she left her phone in the car?" Josie said hopefully.

"Maybe."

Nick tried lifting the roll-up garage door, but it wouldn't budge. Without a word, he opened the rear door of his SUV and rummaged around in the back, emerging with a wire coat hanger. He unwound the hanger, and then stood on his tiptoes in front of the garage door. Gazing through one of the windows, he threaded the hanger up through the top of the door and used the hook to pull the emergency release lever.

"Voila!" he said, pulling the door free. It rolled up easily. "There's no door I can't-"

Nick froze midsentence, staring straight ahead into the garage.