"It wasn't me! I swear it!"

Nero glanced from the protesting Gianna to Sister Benedicta, who was looming over the girl with a deadly expression. "A child was nearly killed yesterday," the headmistress hissed. "If I find you have been lying—"

"Ask Nero!" Gianna pointed to him with a trembling hand. "Il patrono did not want to see me. He even shot at me with his gun! If I had been helping him, would he have treated me this way?"

Sister Benedicta's eyes swiveled to Nero, who nodded. "It's true. He did take a shot at her."

The headmistress allowed some of the animosity to drain from her posture. "Very well. Go to your room and stay there until we have discerned the truth of this matter."

Gianna all but fled, and Nero found himself pitying the girl. She'd had the year from hell, given up her siblings, and nearly lost her fingers; then she'd found out that the mentor she'd trusted had engineered the deaths of her parents, and now the only person who could grant her a safe haven suspected her of colluding to kill a child. "I really don't think it was her," Nero put in. "Lauda basically said she was worthless to him. If she'd been feeding him useful information, he wouldn't have dismissed her so quickly."

"It does seem unlikely," Sister Benedicta agreed with a sigh, "though if she isn't the informant, who is? If what you say is true—that no one else knew of your plans—then it must have been someone here. Perhaps one of the children heard you talking, and shared the information?"

"I suppose we could ask if any of the children have seen or spoken to a man in a cowl when they went outside." Kyrie stepped aside as someone wheeled a cart of dishes past them into the dining hall. "Julio said he'd seen Lauda wearing it more than once. It does make him memorable."

The dish cart slowed, and the woman pushing it turned back toward them. It was Sister Gratia. "I beg your pardon, but did you say a man wearing a cowl had been seen outside?"

"That is what we hope to learn." Sister Benedicta's sharp eyes fixed on Sister Gratia. "Why do you ask?"

"Oh—no reason, I just… thought…" She stammered to a halt, and a flush began to creep up her cheeks.

"Sister Gratia." The headmistress's tone demanded obedience. "Tell us what you know."

"I only thought it might be our benefactor," she blurted. "He wears a cowl sometimes."

"Your benefactor?" Nero frowned. "You mean the guy who's been making all those cash donations?"

Sister Gratia nodded meekly. "I thought if he had been seen, I might go out and meet him. He… prefers that I… accept the gifts."

"Why you, Sister Gratia?" Sister Benedicta's eyes narrowed. "I hope you have not been comporting yourself in an inappropriate manner."

"Oh, no, nothing like that! Nothing inappropriate."

"Then why does he only deliver his gifts through you? What do you give him, in exchange for the money?"

"Nothing!" Sister Gratia flushed pink. "That is, he just… likes me to tell him about the children."

The hair at the nape of Nero's neck rose. "What about the children?"

She shrugged. "Oh, just little things to know how they're doing, and what they've been up to. There are several he's taken a particular interest in. I imagine he wants to know his money is being put to good use."

"Which children?" Nero growled.

"Well…" Sister Gratia looked away.

Nero seized her arm, ignoring her yelp of pain. "Which ones?"

"Nero." Kyrie's hand closed on his wrist, and Nero forced his fingers to release their vise grip.

Sister Gratia's eyes were wide with fear. "T-the ones who live with you," she stammered. "Julio, and Carlo, and the others. He always asks about them."

Nero whirled away and released a stream of profanity the likes of which those venerable halls had never witnessed. Only Sister Benedicta reacted, uttering a low, "Nero."

Kyrie had completely ignored Nero's outburst. She took Sister Gratia gravely by the shoulders. "Did you tell that man about our pistol training session? Did he know that we were going to be away from home yesterday?"

"I… may have mentioned it." Her teeth worried her lower lip. "Why? What does that matter?"

"What does it matter?" Nero rounded on her. "Because that bastard's the one who's been turning demons loose in your backyard. Because yesterday, while I was here trying to save your asses, he broke into my house and kidnapped Julio with a gun to his head. Because my kid almost died because of you!"

Sister Gratia recoiled, tears spilling down her cheeks, while both Kyrie and Sister Benedicta hauled Nero back. It took several echoes of his name before Kyrie's voice penetrated the haze of red that had settled over his vision. "Nero, stop," she repeated, desperation edging into her words. "Stop. You need to calm down."

Nero twisted away and stalked across the deserted dining hall. Kyrie was right; he needed to pull himself together before he did something unforgivable. The blind rage had consumed his self-control and whipped the energy at his core into a firestorm, and now that conflagration sought a target. Sister Gratia had done wrong, but she didn't deserve to be torn limb from limb, which is what his hands itched to do. Where's a demon when you need one?

Across the room, Sister Gratia was bawling an apology. "I know we aren't meant to tell outsiders about the children, but we needed the money so badly," she sobbed. "He was so generous when I told him what he wanted to know. But I would never have said a word if I'd known he would hurt anyone!"

Nero wasn't in a forgiving mood. He headed for the exit and slammed out into the courtyard, filled with slanting morning sunlight and pleasant birdsong. "Really?" He glared up at the cloudless sky. "Could you not read the room?"

In one corner of the garden was a neat stack of bricks, left over from the repairs the orphanage had needed to make in the aftermath of the Savior's fall. Nero picked one up and clenched it in his right fist, savoring its rough texture, the way the sharp corners bit into his flesh, the resistance it gave against his grip. He poured all his anger and aggression into that hand.

The brick exploded in a shower of red dust.

"Okay," Nero breathed, brushing brick powder off his hands and clothing. "I feel a little bit better now."

An impressed whistle sounded from behind him, and he spun toward the building to see Gianna leaning out a nearby window. He'd completely forgotten that the deserted wing along that side of the courtyard was also the location of her private room.

"Uh, hey." Nero tucked his hands into his pockets. "Didn't know I had an audience."

"I have never seen anyone crush a brick with bare hands before." She propped her elbows on the windowsill and dropped her chin into her palms. "I think you were right. I need to get a lot stronger before I can hunt devils as well as you."

"Or you could, you know, get a real job."

She shook her head. "I don't have any skills. I quit school to take care of Scipio and Flavia, and hunting is the only job I've ever had."

"Why not go back to school? The sisters can get you enrolled."

Her face fell. "I don't think they will help me now. They think I was part of kidnapping that boy."

Nero's instinctual anger flared again, but he suppressed it. "No, you're off the hook for that. We know how Lauda was getting his information now."

"You do?" She sagged in relief. "Then I am not in trouble?"

"Not for that, no. Now, there's still the matter of my van tires, and Nico's gun…"

This time she wilted completely, until her cheek rested on the windowsill and her arms dangled over the edge. "I will be in debt as long as I live," she moaned. "The hospital wants a lot of money. And I owe you for fixing my Vespa, too."

"Nah, the scooter repair's on me. But if you're ever gonna get out from under those hospital bills, then you really ought to think about finding a job that pays better than devil hunting."

"Do you know of any work I could do?"

Nero shrugged. "Wait tables? Dig ditches? Tutor students who are about to fail Italian?"

She blinked. "Is that a paying job?"

"Depends on how badly they're failing."

Gianna screwed up her face in a scowl, and abruptly she ceased to be a starveling would-be devil hunter subsisting on hate and desperation. In that moment, draped over the windowsill with her nose crinkled at Nero's attempt at humor, she was just an ordinary teenage girl.

Sister Benedicta was right; this place had been good for her.

"Nero?" Kyrie's voice echoed across the courtyard, and Nero waved a casual farewell to Gianna as he went to meet her. "There you are! Are you all right, now?"

"Yeah. Sorry about before, I just…"

"I know. We can talk about it later." She glanced back toward the dining hall. "Sister Gratia is confined to her quarters for now. Even if Sister Benedicta decides not to discipline her for breaking the rules, she's so upset that she's in no condition to work. But she was on kitchen staff today, and that leaves them shorthanded…"

Nero sighed. "And you want to stay and help, right?"

"I knew you'd understand." She gave him a grateful smile. "Can you manage all right without me?"

"Sure. I'm just going to finish all the house stuff I didn't get done yesterday."

"Don't overwork yourself! You had a serious injury last night."

"Which has already completely healed." Nero patted his ribs to reassure her. "I'm fine, really. And I feel a whole lot better knowing that Lauda no longer has a direct line on our movements."

"So do I." She shook her head. "It's just so surreal. I can hardly believe he's responsible for all of this. I still get chills when I think about what happened to Julio."

"Yeah, me too. At least we know Julio's safe now. In fact, I should probably go make sure he's studying for his make-up exam."

"All right. I'll be home in time for dinner." She stretched up for a kiss. "And don't work too hard. I mean it!"

Nero rolled his eyes. "Yes, ma'am."

When he arrived home, Lady and Trish were standing in the open garage, dressed to go out—Trish in her usual black getup, and Lady in full motorcycle leathers and holsters. "Did something happen?" he asked.

"No, we just wanted to be ready to go as soon as you two got back." Lady looked over his shoulder. "Where's Kyrie?"

"Still at the orphanage." Briefly Nero filled them in on what they'd learned. "So at least we've blocked the information leak."

Lady shook her head. "It almost always comes down to human error. I doubt any of the sisters will be tempted to bend those privacy rules in the future."

"Yeah. So where are you two headed?"

"Three," Trish said. "We thought we'd take Tony with us."

"Assuming you don't object," Lady added.

Nero shrugged. "I guess that depends on where you're planning on taking him."

"We thought we'd do a little old-fashioned wardriving." Nero returned a blank look, and Lady sighed. "Oh, right. You don't have Internet access here, do you."

"Not to speak of. What's wardriving?"

"It's when you pick up a wireless—wait, that doesn't matter. We're going to drive past Lauda's known haunts and see if Tony can sense him. If we can figure out where he is—or better yet, if Trish can get his scent so she can find him in the future—we'll be in a better position to take him out."

"Okay." Nero frowned. "But how many haunts do we know of? We didn't even know Lauda was alive until yesterday."

"Well, you said Julio saw him at the park, and we know he's been to the orphanage. And then there's Order headquarters, which seems the most likely place."

"True." Nero glanced toward the house. "I guess it's fine to take Tony, as long as you don't engage while he's with you. Remember, Lauda's original plan was to kill him."

"We won't. This is strictly a reconnaissance mission."

"I'll go let him know he can come with us." Trish headed into the house, stepping around Lady's motorcycle.

Nero's gaze fell on the bike. "Wait—how are you going to fit Tony on the bike?"

"Well…" Lady leaned back against the van, patting the fender. "I was going to ask to borrow your keys."

"I thought you were going for stealth? That thing's about as low-profile as a bomb going off."

Lady shrugged. "If he thinks you're out looking for him, he might show up here. Then you'd get a free shot at him."

"Fine." Nero reluctantly dug his keys out of his pocket. "But you so much as scratch that thing, and I will tell Nico that you took it for a joyride without asking."

"Relax. I've driven it before."

"Yeah, I remember. My life still flashes before my eyes whenever you go near the driver's door." Nero tossed her the keyring. "Make sure Tony wears a seat belt."

The door to the house opened, and a white-capped streak barreled out, followed a second later by Trish. "I think someone's a little bit excited to get out of the house," Trish said dryly.

Rosso was already bouncing in place beside the passenger door. "Can I sit up front?"

It took a few minutes for them to load Lady's weapons and arrange themselves in the vehicle. Nero waited until the van had pulled out and rattled down the block, then locked the overhead door and tried to enter the house. The doorknob refused to turn. Nero swore under his breath. It must have been set to lock when Trish had come out.

Nero knocked loudly on the door, hoping that Julio was close enough to this end of the house to hear it. He was just about to knock a second time when the door opened. Vergil stood there, wearing the faintest of frowns. Nero stared back. "Uh, hi. I mean—thanks. I gave Lady my keys and didn't realize the door was locked." Vergil stepped back without a word, and Nero moved into the house, feeling foolish. "Sorry if I interrupted your reading or whatever."

"You didn't." Vergil turned back toward the living room.

Nero paused to hang up his coat, then glanced toward Vergil again. "Wait a second—they took Tony with them because they needed him to sense Lauda's presence or whatever. But you were around Lauda even longer than he was. Why didn't you go with them?"

Vergil sat in his usual chair and cracked open a book. "They didn't ask."

Nero detected the crisp undercurrent beneath the words, but wasn't sure if Vergil was annoyed that he hadn't been invited, or because Nero was continuing to pester him. He decided to cut his losses and headed deeper into the house.

The first sound that greeted him was the rhythmic tumbling of the dryer. The laundry room was deserted, but the dial on the appliance indicated that the cycle had just been started. Nero backtracked to the kitchen, where he found Julio seated at the kitchen table, school books fanned out around him. "Are you doing laundry?"

The boy looked up from his books. "No, but Mister Vergil was in there a few minutes ago."

"Huh." Nero supposed he shouldn't be surprised; after all, the last time he'd been at the shop, Vergil's clothes had been clean and neatly folded, while Dante's had clearly been neglected for some time. He just found it difficult to imagine Vergil doing anything so mundane as measuring out laundry detergent.

Julio was staring at him expectantly. "So? Did you learn anything at the orphanage?"

"Yeah, we did. It's been taken care of." Nero thought it best not to mention any names; he'd traumatized Sister Gratia plenty without heaping coals of child resentment on her head. "Kyrie stayed there to help out, so you're stuck with me for lunch. Any requests?"

"Hmm. How about something raw?"

"Raw?"

Julio failed to keep the laugher out of his voice. "I mean, you can't burn what you don't cook, right?"

Nero turned to scowl at him, then took a closer look. "Man, your face looks even worse than it did at breakfast."

Julio gingerly touched his puffy cheek. "Yeah. It hurts a little less now, but it's turning more colors."

"Well, at least the school will know I wasn't just making excuses when I called in this morning."

"What did you tell them?"

"Just that you'd gotten hurt in an accident, and we were keeping you home for a day in case you started feeling worse and needed to go to the doctor." Nero pushed up his sleeves and began washing his hands. "I figured you could make up your own cover story. Just make sure it's believable."

Julio frowned. "Why can't I just tell them the truth? I think getting kidnapped is an excused absence."

"Yeah, but it leads to a lot of awkward questions like why someone kidnapped you, and why we didn't report it, and how we got you back from someone violent enough to leave you looking like that." Nero opened the refrigerator and took stock of his options. "And considering Lauda was using the orphanage to spy on you, it would look bad for them, too. They don't need any bad press. How do you feel about peanut butter?"

"I like peanut butter. I guess it needs to be something they can't check up on." Julio tapped his pencil on the table. "What if a car lost control and jumped the curb, and I had to dive out of the way?"

"Hey, that's pretty good. A near-miss-and-run with no witnesses. You want jam or sliced banana?"

"Can I have both?"

"I don't see why not." He dropped bread in the toaster and began gathering the other ingredients, grateful that Julio seemed to have bounced back quickly from his traumatic experience. Nero had spent a good part of the morning worrying about how the previous day's events would affect him. "How's studying going?"

"Slowly. I'm trying to review everything Mr. Spinalzo said would be on the test, but there's a lot."

"Anything I can help with?"

Julio shook his head. "It's a history test."

"And you're worried? I thought you liked history."

"I do. At least, I like the stories about people who lived a long time ago, but I'm not very good at remembering what year things happened. There are a lot of names and dates to memorize."

"Well, you have the whole afternoon to learn them."

"Not the whole afternoon. I also have algebra homework." Julio made a face.

"In that case, you should take a break and let your brain rest for a couple minutes while you eat this." Nero deposited a plate with the peanut butter sandwich beside Julio's elbow, then returned to the counter to make one for himself. He briefly wondered if he should prepare something for Vergil, but decided against it. Vergil had seemed fairly engrossed in his reading, and if the man was comfortable enough in the house to make use of the laundry facilities, he was more than capable of making himself a sandwich when he was ready for one.

After they ate, Julio returned to his books, and Nero collected their plates and added them to the collection already soaking in the sink. He and Kyrie had left for the orphanage immediately after breakfast, leaving cleanup for later—which was now. Nero rolled up his sleeves and dove in.

He was down to the last few utensils when Julio spoke again. "Nero… can I ask you something?"

Nero glanced back over his shoulder. "Sure. History or algebra?"

"It's not about homework." Julio fidgeted with his pencil. "It's about… what happened yesterday."

Nero's stomach plummeted a few inches. He set the spatula he was scrubbing aside and dried his hands. He didn't want to talk about this with his back to Julio. "Okay."

"I was hoping you could explain what happened." Julio gnawed at his lower lip. "When I fell."

Nero sucked in a breath. He'd been dreading this, and a part of him had hoped that Julio wouldn't remember what he'd done. "I had to let go, Julio. I'm really sorry. You have every reason to be furious with me for scaring you like that."

"What?" Julio blinked up at him. "No, I don't mean that."

Nero stared back. "You don't?"

"No. I'm not mad or anything." The boy cocked his head. "Did you think I was mad?"

"I… guess I was afraid you might be. Because I couldn't pull you up, and then I dropped you."

"It wasn't your fault, though. You were hurt, right?"

"Yeah. Lauda stabbed me when I was trying to catch you."

Julio scowled. "That guy's an asshole. And he's crazy."

"Language," Nero chided. "Kyrie will kick both our butts if she hears you talking like that." He stretched his arms over his head. The wound had healed, but an echo of the pain in his side remained. "But just between us, you're not wrong. Guy's a total nutjob." He pulled out a chair and sat across from Julio. "So if it wasn't about me letting go of you, what were you really asking?"

"I know all sorts of weird stuff happens to your brain when you think you're about to die, but I saw some really strange things, and I don't know if any of it was real or if I hallucinated all of it."

"What do you remember seeing?"

Julio's brow crinkled. "Well, I was falling, and then for a second it was like someone was falling with me. And then suddenly we weren't falling at all; we were in this weird, creepy place. It was like… like being inside a body, or something. Everything was red and slimy and pulsing, like a giant heart, and it smelled really bad. And I looked around, and Mister Vergil was there with me, and there were all these weird monsters. Really ugly ones, like giant bugs."

Nero nodded. "Demons, probably."

"They didn't sound like the kind you told me about. None of them looked like scarecrows or plants or anything."

"There are lots of different kinds. What else happened?"

"Well, the bug things came at us, and then Mister Vergil stood up, and they all just stopped and backed away, like they were scared of him or something."

Well, that was interesting. "I guess Urizen is still king of the underworld," Nero muttered.

Julio looked puzzled. "Who?"

"Never mind. Sorry, didn't mean to interrupt. What next?"

"Then Mister Vergil picked me up, and we started falling again, and then all of a sudden we were back behind that collapsed building with you. It was like the freakiest dream ever, and I don't know what really happened." He lifted anxious eyes to Nero. "I couldn't sleep much last night. I just kept seeing that place and getting freaked out. What happened? How did we end up back there with you after I fell off the edge?"

Nero blew out a long breath. "Um. Okay. This is really complicated…"

Julio frowned. "So far you've told me about demons, and that your real job is hunting them, and how the earthquake is just a big conspiracy, and about you finding your family, and growing a new arm, and the fact that everyone on the island used to worship your grandpa and you have superpowers and can make your arm disappear because you're only part human. How much more complicated can it be?"

Nero laughed. "Okay, maybe it's not that complicated. Vergil has superpowers, too. He can do this thing where he sort of warps through space. Like teleporting, basically."

"Teleporting?" Julio blinked a few times. "Okay, maybe this is more complicated than I thought."

"Superpowers, remember?" Nero held up his right hand and phased it out for a few seconds as an illustration. "He teleported down, caught you mid-air, took you on a detour through a portal to another world, and then brought you back to this world in a different spot."

"Hold on!" Julio slapped his palms down on the table. His pencil jumped and rolled away. "When you say another world…"

"Well, another… plane of existence, I guess? Or dimension, maybe? I'm not sure what it is, technically. Science was never my thing."

Julio's eyes were stretched almost comically wide. "Another plane, meaning… where, exactly?"

"The underworld. Where demons come from."

"The underworld," Julio echoed. "Where demons come from. It's a real place?"

"Of course." Nero cocked his head to one side. "You know demons are real. They have to come from somewhere, right?"

"I… guess I never really thought about where they came from." Julio looked down at the table for a moment, then back up. "And… I was there?"

"Sure sounds like it." Nero propped his elbows on the table. "It's pretty rare for humans to see it, though. You could be the only human alive who's been there. I'll have to ask Lady if she's ever been."

Julio moistened his lips. "Have you been there?"

"Hmm. Maybe? I'm not sure. I was inside a demon tree that kind of grew its own version of it, I think, but I don't know if I ever made it to the underworld itself." Nero shook his head. "Now that's complicated. Don't ask me about the tree thing; I don't even know where to start on that one."

"Okay." Julio was looking a little overwhelmed. "But Vergil's been to the underworld?"

"Obviously. That's how he knew where to take you."

"Why would anyone want to go there, if it's full of demons?"

"Good question." Nero raised his eyes over Julio's head to the figure lurking in the doorway. "Why would anyone want to go to the underworld, if it's full of demons?"

Julio twisted in his seat to stare up at Vergil with wide eyes. Vergil seemed not to notice the boy's reaction. "Why would anyone want to come to the human world, if it's full of humans?" he countered as he crossed to the sink. He filled the kettle and put it on the stove—a task that suddenly seemed to Nero even more bizarrely mundane than doing laundry, considering Vergil was evidently still respected as the emperor of the underworld. He probably had some demonic minion there whose job it was to put the kettle on. Did they even have tea kettles in hell? Now there was an existential question the Order had never tackled.

Julio clearly didn't interpret Vergil's question as rhetorical. "I guess… if demons wanted to eat the humans, they'd come here. But humans don't eat demons. So why would a human go there?"

"I can't imagine," Vergil said mildly.

Julio's brows scrunched together. "But you went there. You had to have some reason."

"I did." Vergil spent a few seconds arranging his mug and tea bag to his satisfaction. "But I am not a human."

Julio stared up at Vergil as though seeing him for the first time, and Nero could see the truth really sinking in. "You're half human, right?"

"Only half."

"So… I guess that means you could live in either place? Because half of you is from each world." Julio absorbed this for a moment, and his eyes flicked back to Vergil. "But you look human."

One corner of Vergil's mouth twitched upward. "Not always."

The kettle whistled, and Vergil filled his mug and left the room. Julio slumped back in his seat. "You're right," he said, raising wide eyes to Nero. "It's really complicated."

Vergil was halfway through the cup of tea when Nero joined him in the living room. It had taken the better part of ten minutes to get Julio focused on his homework again, and Nero thought it best to leave the last few dishes for later rather than stay where the boy could continue peppering him with questions.

Vergil was, predictably, deeply engrossed in a book. Nero watched him read for a few minutes, marveling at the speed with which he absorbed the text. Eventually the silence became too smothering, and Nero felt compelled to break it. "Where have you spent more time?" he asked suddenly.

Vergil glanced up. "Pardon?"

"Which world have you spent the most time in?"

Vergil closed the book, though he left a finger tucked between the pages to mark his place. "It's difficult to say. Time passes differently in the underworld."

"You were nineteen when you went there, right?"

Vergil's expression remained perfectly neutral. "You're well-informed."

Nero shrugged. "Lady told me. She was there when you jumped."

"She wasn't," Vergil said crisply. "Though I have no doubt Dante told her about it afterward."

Nero decided he had better things to unpack than the bizarre antagonism between Vergil and Lady. "So nineteen years here, and then you spent the rest of the time in the underworld, until you showed up last year? So that's what, another twenty-five years that you weren't on this plane?"

Vergil shook his head. "I wasn't in the underworld all that time."

"You came back before?"

"I…" Vergil faltered, which was out of character. "My memories of that time are incomplete."

"You mean you didn't get them all back?"

"More that I never had them in the first place." He looked down at the book, though his gaze was distant. "I know I spent some time in this world, but I can't account for all of those years based on my own memory. So I'm afraid I can't answer your question with any degree of accuracy."

Nero settled back on the couch. That question had only been an oblique approach to what he really wanted to know. "You really don't consider yourself human, do you."

Vergil observed him. "Does that bother you?"

"I don't know." Nero stared out the window. "It sure does explain a lot, though."

"Such as?"

His cool, impassive tone fueled Nero's frustration. "How you can wipe out an entire city full of people and not give a damn. I guess to you, our lives don't matter any more than a demon's would to a random person on the street."

"Our lives?" Vergil echoed. "You aren't fully human, either."

"No, but I sure as hell identify as one." Nero pushed to his feet. "I don't hate having this power, but it doesn't define me. Everything I care about, everything I want to protect, is right here in this world. And that's all I need to tell me who I am."

He turned to leave, but Vergil's voice stopped him. "Nero."

Nero half-turned to bring him into his peripheral vision. He couldn't quite bring himself to face him directly. "What?"

"I don't consider myself a human. Nor do I consider myself a devil."

Nero frowned. "What do you consider yourself, then?"

Vergil's chin was high as he answered, with absolute conviction, "Unique."

Nero did look at him then, but Vergil had already returned to his book.