THEY EMERGED IN CENTRAL PARK just north of the Pond. Mrs. O'Leary looked pretty tired as she limped over to a cluster of boulders. She started sniffing around, and at Percy's worried look, Nico said, "It's okay. She just smells the way home."

Percy frowned. "Through the rocks?"

"The Underworld has two major entrances," Naomi explained. "We went to the one in L.A., with Charon's ferry. That's the way most souls go, but there's a smaller path, harder to find. The Door of Orpheus."

"The dude with the harp," Percy said.

"The dude with the lyre," Nico corrected. "But, yeah, him. He used his music to charm the earth and open a new path into the Underworld. He sang his way right into Hades's palace and almost got away with his wife's soul."

The story of Orpheus and Eurydice had always been Naomi's favorite—not because it made her happy, of course. She cried every time she heard a new rendition of it, because it always ended the same: with Orpheus looking back.

Most people thought he was a fool for looking back and damning Eurydice to return back to the Underworld, but Naomi saw the story differently. Whichever version you read—whether Orpheus turned because he worried Eurydice wasn't following, or he turned because she tripped, or he turned because he'd been so excited to see her again he hadn't realized they both weren't out of the Underworld—the message was the same: his love for Eurydice was what made him turn.

Ovid had said, as Eurydice's soul was pulled back into the Underworld, What was there to complain of, but that she had been loved?

Naomi used to wonder what it felt like to love or be loved like that.

Now, she thought she understood.

"So this is the Door of Orpheus," Percy said. "How does it open?"

"We need music," Nico said. "Either of you good at singing?"

"Drew said her cat screaming while getting a bath sounds better than my singing," Naomi admitted sheepishly. "Percy?"

"Um, no," he said. "Can't you guys just, like, tell it to open? You're children of the Underworld and all."

"It's not so easy," Nico said. "We need music."

"I have a better idea," Percy decided. He turned and called, "GROVER!"

❊

They waited for a long time. Mrs. O'Leary curled up and took a nap. Naomi could hear the crickets in the woods and an owl hooting. Traffic hummed along Central Park West. Horse hooves clopped down a nearby path—maybe a mounted police patrol. Naomi was sure they'd love to find three kids hanging out in the park at one in the morning.

"It's no good," Nico said at last.

Percy shut his eyes, the space between his brows wrinkling in concentration. A few moments later, he almost fell over.

"What happened?" Naomi asked, holding his arm to steady him.

"I got through," Percy said. "He's... yeah. He's on his way."

A minute later, the tree next to them shivered. Grover fell out of the branches, right on his head.

"Grover!" Perch yelled.

"Woof!" Mrs. O'Leary looked up, probably wondering if they were going to play fetch with the satyr.

"Blah-haa-haa!" Grover bleated.

"You okay?" Naomi asked.

"Oh, I'm fine." He rubbed his head. His horns had grown so much they poked right out of his curly hair. "I was at the other end of the park. The dryads had this great idea of passing me through the trees to get me here. They don't understand height very well."

He grinned and got to his feet—well, his hooves, technically. Since last summer, Grover had stopped trying to disguise himself as human. He never wore a cap or fake feet anymore. He didn't even wear jeans, since he had furry goat legs from the waist down. His T-shirt had a picture from that book Where the Wild Things Are. It was covered with dirt and tree sap. His goatee looked fuller, almost manly (or goatly?), and he was as tall as Percy now.

"Good to see you, G-man," Percy said. "You remember Nico."

Grover nodded at Nico, then gave Percy and Naomi big hugs. He smelled like freshly mown lawns.

"I've missed you guys!" he said. "I miss camp. They don't serve very good enchiladas in the wilderness."

"We were worried," Percy said. "Where've you been the last two months?"

"The last two—" Grover's smile faded. "The last two months? What are you talking about?"

"We haven't heard from you," Percy said. "Juniper's worried. We sent Iris-messages, but—"

"Hold on." Grover looked up at the stars like he was trying to calculate his position. "What month is this?"

"August."

The color drained from his face. "That's impossible. It's June. I just lay down to take a nap and..." He grabbed Percy's arms. "I remember now! He knocked me out. Percy, we have to stop him!"

"Whoa," Percy said. "Slow down. Tell us what happened."

He took a deep breath. "I was... I was walking in the woods up by Harlem Meer. And I felt this tremble in the ground, like something powerful was near."

"You can sense stuff like that?" Nico asked.

Grover nodded. "Since Pan's death, I can feel when something is wrong in nature. It's like my ears and eyes are sharper when I'm in the wild. Anyway, I started following the scent. This man in a long black coat was walking through the park, and I noticed he didn't cast a shadow. Middle of a sunny day, and he cast no shadow. He kind of shimmered as he moved."

"Like a mirage?" Nico asked.

"Yes," Grover said. "And whenever he passed humans—"

"The humans would pass out," Nico said. "Curl up and go to sleep."

"That's right! Then after he was gone, they'd get up and go about their business like nothing happened."

Naomi stared at Nico. "You know this guy in black?"

"Afraid so," Nico said. "Grover, what happened?"

"I followed the guy. He kept looking up at the buildings around the park like he was making estimates or something. This lady jogger ran by, and she curled up on the sidewalk and started snoring. The guy in black put his hand on her forehead like he was checking her temperature. Then he kept walking. By this time, I knew he was a monster or something even worse. I followed him into this grove, to the base of a big elm tree. I was about to summon some dryads to help me capture him when he turned and..."

Grover swallowed. "His face. I couldn't make out his face because it kept shifting. Just looking at him made me sleepy. I said, 'What are you doing?' He said, 'Just having a look around. You should always scout a battlefield before the battle.' I said something really smart like, 'This forest is under my protection. You won't start any battles here!' And he laughed. He said, 'You're lucky I'm saving my energy for the main event, little satyr. I'll just grant you a short nap. Pleasant dreams.' And that's the last thing I remember."

Nico exhaled. "Grover, you met Morpheus, the God of Dreams. You're lucky you ever woke up."

"Two months," Grover moaned. "He put me to sleep for two months!"

"Why didn't the nymphs try to wake you?" Percy asked.

Grover shrugged. "Most nymphs aren't good with time. Two months for a tree—that's nothing. They probably didn't think anything was wrong."

"We've got to figure out what Morpheus was doing in the park," Percy said. "I don't like this 'main event' thing he mentioned."

"He's working for Kronos," Nico said. "We know that already. A lot of the minor gods are. This just proves there's going to be an invasion. Percy, we have to get on with our plan."

"Wait," Grover said. "What plan?"

They told him, and Grover started tugging at his leg fur.

"You're not serious," he said. "Not the Underworld again."

"I'm not asking you to come, man," Percy promised. "I know you just woke up. But we need some music to open the door. Can you do it?"

Grover took out his reed pipes. "I guess I could try. I know a few Nirvana tunes that can split rocks. But, Percy, are you sure you want to do this?"

"Please, man," Percy said. "It would mean a lot. For old times' sake?"

He whimpered. "As I recall, in the old times we almost died a lot. But okay, here goes nothing."

He put his pipes to his lips and played a shrill, lively tune. The boulders trembled. A few more stanzas, and they cracked open, revealing a triangular crevice.

Naomi looked inside. Steps led down into the darkness, the air rich with the smell of mildew and death.

Percy turned to Grover. "Thanks... I think."

"Perrrrcy, is Kronos really going to invade?"

"I wish I could tell you better, but yeah. He will."

Naomi thought Grover might chew up his reed pipes in anxiety, but he straightened up and brushed off his T-shirt. "I've got to rally the nature spirits, then. Maybe we can help. I'll see if we can find this Morpheus.'"

"Better tell Juniper you're okay, too."

His eyes widened. "Juniper! Oh, she's going to kill me!"

He started to run off, then scrambled back and gave Percy one last hug. "Be careful down there! Come back alive!"

Once he was gone, they roused Mrs. O'Leary from her nap.

When she smelled the tunnel, she got excited and led the way down the steps.

"Ready?" Nico asked. "It'll be fine. Don't worry."

It sounded like he was trying to convince himself more than Percy.

Naomi took a deep breath, and the trio plunged into darkness.

❊

The stairs went on forever—narrow, steep, and slippery. It was completely dark save for the light of Percy's sword.

They tried to move slowly, but Mrs. O'Leary had other ideas. She bounded ahead, barking happily. The sound echoed through the tunnel like cannon shots. They certainly didn't have the element of surprise—Naomi just hoped they wouldn't need it.

Nico lagged behind, which was strange.

"You okay?" Naomi asked him.

"Fine," he said. "Just keep moving."

Naomi and Percy didn't have much of choice. They followed Mrs. O'Leary into the depths. As they walked, Naomi half-expected Skia to appear, sensing her presence in the Underworld, but there was no sign of the beast. Naomi hoped she was just busy playing with Cerberus.

After an hour of walking, Naomi started to hear the roar of a river.

They emerged at the base of a cliff, on a plain of black volcanic sand. To their right, the River Styx gushed from the rocks and roared off in a cascade of rapids. To their left, far away in the gloom, fires burned on the ramparts of Erebus, the great black walls of Hades' kingdom.

Like the first time they'd visited the Underworld, Percy reached for Naomi's hand. Naomi was too nervous about their plan to even notice the butterflies going crazy in her stomach.

Mrs. O'Leary ran along the beach, picked up a random human leg  bone, and romped back toward them. She dropped the bone at Percy's feet and waited for him to throw it.

"Um, maybe later, girl." He stared at the dark waters. "So, Nico... how do we do this?"

"We have to go inside the gates first," Nico said.

"But the river's right here."

"I have to get something," he said. "It's the only way."

He marched off without waiting.

Naomi and Percy shared a look, but there wasn't much they could do except follow.

Lines of the dead stood outside waiting to get in. It must've been a heavy day for funerals, because even the EZ-DEATH line was backed up.

"WOOF!" Mrs. O'Leary said. Before anyone could stop her, she bounded toward the security checkpoint. Cerberus appeared out of the gloom, greeting Mrs. O'Leary. Naomi frowned—still no sign of Skia.

She wondered when it was appropriate to start worrying.

"Mrs. O'Leary, no!" Percy shouted at her. "Don't sniff—oh, man."

Nico smiled. Then he looked at them and his expression turned serious again, like he'd remembered something unpleasant. "Come on. They won't give us any trouble in the line."

They slipped through the security ghouls and into the Fields of Asphodel. Percy had to whistle for Mrs. O'Leary three times before she left Cerberus alone and ran after them.

They hiked over black fields of grass dotted with black poplar trees. Nico trudged ahead, bringing them closer and closer to the palace of Hades.

"Hey," Naomi called to him, "we're inside the gates already. Where are we—"

Mrs. O'Leary growled. A shadow appeared overhead—something dark, cold, and rotten. It swooped down and landed in the top of a poplar tree.

Unfortunately, Naomi recognized her. She had a shriveled face, a horrible blue knitted hat, and a crumpled velvet dress. Leathery bat wings sprang from her back. Her feet had sharp talons, and in her brass-clawed hands she held a flaming whip and a paisley handbag.

"Mrs. Dodds," Percy said.

She bared her fangs. "Welcome back, honey."

Her two sisters—the other Furies—swooped down and settled next to her in the branches of the poplar.

"You know Alecto?" Nico asked Percy.

"If you mean the hag in the middle, yeah," Percy said. "She was our math teacher."

Nico nodded, like he wasn't all that surprised. He looked up at the Furies and took a deep breath. "I've done what my father asked. Take us to the palace."

Percy tensed. "Wait a second, Nico. What do you—"

"I'm afraid this is my new lead, Percy. My father promised me information about my family, but he wants to see you before we try the river. I'm sorry."

"What?" Naomi demanded. "You lied?"

Percy lunged at Nico, but Mrs. Dodds/Alecto swooped down with superhuman speed and grabbed him by the arms. His sword fell out of his hand and hit the dark sand with a dull thud.

Before Naomi could properly react, the second Fury grabbed her, and in seconds she was dangling sixty feet in the air.

Mrs. O'Leary barked angrily and jumped, trying to reach Percy, but they were too high.

"Tell Mrs. O'Leary to behave," Nico warned. He was hovering as well in the clutches of the third Fury. "I don't want her to get hurt, Percy. My father is waiting. He just wants to talk."

Percy's jaw ticked. "Mrs. O'Leary, down! It's okay, girl."

She whimpered and turned in circles, looking up at him.

"All right, traitor," Percy growled at Nico. "You've got your prize. Take me to the stupid palace."

❊

The Fury placed Naomi on her feet in the middle of the palace garden.

Mrs. Dodds, on the other hand, dropped Percy like a sack of turnips onto the ground.

Naomi had been in this garden plenty of times before, and it was just as beautifully strange as she remembered. Skeletal white trees grew from marble basins. Flowerbeds overflowed with golden plants and gemstones. A pair of thrones, one bone and one silver, sat on the balcony with a view of the Fields of Asphodel.

Skeletal warriors guarded the only exit. They wore tattered U.S. Army desert combat fatigues and carried M16s.

The third Fury deposited Nico next to Naomi. Then all three of them settled on the top of the skeletal throne.

At the empty thrones, the air shimmered. Three figures appeared—Hades and Persephone on their thrones and Demeter standing between them. They seemed to be in the middle of an argument.

"—told you he was a bum!" Demeter said.

"Mother!" Persephone replied.

"We have visitors!" Hades barked. "Please!"

Naomi's stepfather smoothed his black robes, which were covered with the terrified faces of the damned.

The annoyance in Persephone's expression melted into something softer as she laid eyes on her daughter. "Kore, it's so lovely to see you again."

Naomi narrowed her eyes. She was not in the mood for a mother-daughter reunion right now.

"Percy Jackson," Hades said with satisfaction. "At last."

"Humph," Demeter said. "More demigods. Just what we need."

Naomi frowned. "Nice to see you too, Grandmother."

Demeter's expression softened. "Oh, I don't mean you, dear," she said. "It's always lovely to see you. Your friends, on the other hand..."

Nico stepped forward, kneeling. "Father," he said. "I have done as you asked."

"Took you long enough," Hades grumbled. "Your sister would've done a better job."

Nico lowered his head. Despite the fact that he'd just betrayed them, Naomi couldn't help but feel bad for him.

Percy glared at the god of the dead. "What do you want, Hades?"

"To talk to you, of course." The god twisted his mouth in a cruel smile. "Didn't Nico tell you?"

"So this whole quest was a lie," Percy said. "Nico brought me down here to get me killed."

"Oh, no," Hades said. "I'm sure I'd never hear the end of it from my stepdaughter if I did such a thing. And I'm afraid Nico was quite sincere about wanting to help you. The boy is as honest as he is dense. I simply convinced him to take a small detour and bring you here first."

"Father," Nico said, "you promised that Percy would not be harmed. You said if I brought him and Naomi, you would tell me about my past—about my mother."

Persephone let out a dramatic sigh. "Can we please not talk about that woman in my presence?"

Naomi resisted the urge to call her own mother a hypocrite.

"I'm sorry, my dove," Hades said. "I had to promise the boy something."

Naomi's grandmother harrumphed. "I warned you, daughter. This scoundrel Hades is no good. You could've married the god of doctors or the god of lawyers, but noooo. You had to eat the pomegranate."

"Mother—"

"And here it is, August, and do you come home like you're supposed to? Do you ever think about your poor lonely mother?"

"DEMETER!" Hades shouted, clearly miffed. "That is enough. You are a guest in my house."

"Oh, a house is it?" she said. "You call this dump a house? Make my daughter live in this dark, damp—"

"I told you," Hades said, grinding his teeth, "there's a war in the world above. You, Persephone, and Naomi are better off here."

"Whoa, when did I get roped into this?" Naomi asked. "I'm not staying down here!"

"Well..." Persephone started to say, then thought better of it.

"Excuse me," Percy broke in, "but if you're going to kill me, could you just get on with it?"

Naomi smacked him in the arm as all three gods looked at him.

"Well, this one has an attitude," Demeter observed.

"Indeed," Hades agreed. "I'd love to kill him."

"Absolutely not!" Naomi shouted.

"Father," Nico said. "You promised!"

"Husband, we talked about this," Persephone chided. "You can't go around incinerating every hero. Besides, he's brave. I like that."

Hades rolled his eyes. "You liked that Orpheus fellow, too. Look how well that turned out. Let me kill him, just a little bit."

"Father, you promised!" Nico said. "You said you only wanted to talk to him! You said if I brought him, you'd explain."

Hades glowered, smoothing the folds of his robes. "And so I shall. Your mother—what can I tell you? She was a wonderful woman." He glanced uncomfortably at Persephone. "Forgive me, my dear. I mean for a mortal, of course. Her name was Maria di Angelo. She was from Venice, but her father was a diplomat in Washington, D.C. That's where I met her. When you and your sister were young, it was a bad time to be children of Hades. World War II was brewing. A few of my, ah, other children were leading the losing side. I thought it best to put you two out of harm's way."

"That's why you hid us in the Lotus Casino?"

Hades shrugged. "You didn't age. You didn't realize time was passing. I waited for the right time to bring you out."

"But what happened to our mother? Why don't I remember her?"

"Not important," Hades snapped.

"What? Of course it's important. And you had other children—why were we the only ones who were sent away? And who was the lawyer who got us out?"

Hades gritted his teeth. "You would do well to listen more and talk less, boy. As for the lawyer..."

Hades snapped his fingers. On top of his throne, the Fury Alecto began to change until she was a middle-aged man in a pinstriped suit with a briefcase.

"You!" Nico said.

The Fury cackled. "I do lawyers and teachers very well!"

Nico was trembling. "But why did you free us from the casino?"

"You know why," Hades said. "This idiot son of Poseidon cannot be allowed to be the child of the prophecy."

Percy plucked a ruby off the nearest plant and threw it at Hades. Not a very effective attack strategy, but okay. "You should be helping Olympus!" he said. "All the other gods are fighting Typhon, and you're just sitting here—"

"Waiting things out," Hades finished. "Yes, that's correct. When's the last time Olympus ever helped me, half-blood? When's the last time a child of mine was ever welcomed as a hero? Bah! Why should I rush out and help them? I'll stay here with my forces intact."

"And when Kronos comes after you?"

"Let him try. He'll be weakened. And my son here, Nico—" Hades looked at him with distaste. "Well, he's not much now, I'll grant you. It would've been better if Bianca had lived. But give him four more years of training. We can hold out that long, surely. Nico will turn sixteen, as the prophecy says, and then he will make the decision that will save the world. And I will be king of the gods."

"You're crazy," Percy said. "Kronos will crush you, right after he finishes pulverizing Olympus."

Hades spread his hands. "Well, you'll get a chance to find out, half-blood. Because you'll be waiting out this war in my dungeons."

"What?" Naomi demanded.

"No!" Nico said. "Father, that wasn't our agreement. And you haven't told me everything!"

"I've told you all you need to know," Hades said. "As for our agreement, I spoke with Jackson. I did not harm him. You got your information. If you wanted a better deal, you should've made me swear on the Styx. Now go to your room!" He waved his hand and Nico vanished.

"That boy needs to eat more," Demeter grumbled. "He's too skinny. He needs more cereal."

Persephone rolled her eyes. "Mother, enough with the cereal."

"Mom, you can't let him do this!" Naomi shouted.

Persephone considered her daughter for a moment, then looked at her husband. "My lord Hades, are you sure we can't let this little hero go? He's awfully brave."

"No, my dear. I've spared his life. That's enough."

Naomi looked pleadingly at her mother. "Mom, please."

Persephone's expression was gentle. "I'm sorry, Kore," she said. "Come—I'll show you to your room."

"My room?" Naomi demanded. "I'm not staying he—"

Before Naomi could finish her sentence, Persephone waved a hand, and she was transported out of the throne room.

❊