The cabbie chewed his cigar and sized us up. "That's three hundred miles. For that, you gotta pay up front."

"You accept casino debit cards?" Annabeth asked.

He shrugged. "Some of 'em. Same as credit cards. I gotta swipe 'em through first."

Annabeth handed him her green LotusCash card.

He looked at it skeptically.

"Swipe it," Annabeth invited.

He did.

His meter machine started rattling. The lights flashed. Finally an infinity symbol came up next to the dollar sign.

The cigar fell out of the driver's mouth. He looked back at us, his eyes wide. "Where to in Los Angeles... uh, Your Highness?"

"The Santa Monica Pier." Annabeth sat up a little straighter. I could tell she liked the "Your Highness" thing. "Get us there fast, and you can keep the change."

Maybe she shouldn't have told him that. The cab's speedometer never dipped below ninety-five the whole way through the Mojave Desert.

On the road, we had plenty of time to talk. I told Annabeth and Grover about my latest dream, but the details got sketchier the more I tried to remember them. The Lotus Casino seemed to have short-circuited my memory. I couldn't recall what the invisible servant's voice had sounded like, though I was sure it was somebody I knew. The servant had called the monster in the pit something other than "my lord" ... some special name or title....

"The Silent One?" Annabeth suggested. "The Rich One? Both of those are nicknames for Hades."

"Maybe ..." I said, though neither sounded quite right.

"That throne room sounds like Hades's," Grover said. "That's the way it's usually described."

I shook my head. "Something's wrong. The throne room wasn't the main part of the dream. And that voice from the pit ... I don't know. It just didn't feel like a god's voice."

Annabeth's eyes widened.

"What?" I asked.

"Oh ... nothing. I was just—No, it has to be Hades. Maybe he sent this thief, this invisible person, to get the master bolt, and something went wrong—"

"Like what?"

"I—I don't know," she said. "But if he stole Zeus's symbol of power from Olympus, and the gods were hunting him, I mean, a lot of things could go wrong. So this thief had to hide the bolt, or he lost it somehow. Anyway, he failed to bring it to Hades. That's what the voice said in your dream, right? The guy failed. That would explain what the Furies were searching for when they came after us on the bus. Maybe they thought we had retrieved the bolt."

I wasn't sure what was wrong with her. She looked pale.

"But if I'd already retrieved the bolt," I said, "why would I be traveling to the Underworld?"

"To threaten Hades," Grover suggested. "To bribe or blackmail him into getting your mom back."

I whistled. "You have evil thoughts for a goat."

"Why, thank you."

"But the thing in the pit said it was waiting for two items," I said. "If the master bolt is one, what's the other?"

Grover shook his head, clearly mystified.

Annabeth was looking at me as if she knew my next question, and was silently willing me not to ask it.

"You have an idea what might be in that pit, don't you?" I asked her. "I mean, if it isn't Hades?"

"Percy ... let's not talk about it. Because if it isn't Hades ... No. It has to be Hades."

Wasteland rolled by. We passed a sign that said CALIFORNIA STATE LINE, 12 MILES.

I got the feeling I was missing one simple, critical piece of information. It was like when I stared at a common word I should know, but I couldn't make sense of it because one or two letters were floating around. The more I thought about my quest, the more I was sure that confronting Hades wasn't the real answer. There was something else going on, something even more dangerous.

The problem was: we were hurtling toward the Underworld at ninety-five miles an hour, betting that Hades had the master bolt. If we got there and found out we were wrong, we wouldn't have time to correct ourselves. The solstice deadline would pass and war would begin.

"The answer is in the Underworld," Annabeth assured me. "You saw spirits of the dead, Percy. There's only one place that could be. We're doing the right thing."

She tried to boost our morale by suggesting clever strategies for getting into the Land of the Dead, but my heart wasn't in it. There were just too many unknown factors. It was like cramming for a test without knowing the subject. And believe me, I'd done that enough times.

The cab sped west. Every gust of wind through Death Valley sounded like a spirit of the dead. Every time the brakes hissed on an eighteen-wheeler, it reminded me of Echidna's reptilian voice.

At sunset, the taxi dropped us at the beach in Santa Monica. It looked exactly the way L.A. beaches do in the movies, only it smelled worse. There were carnival rides lining the Pier, palm trees lining the sidewalks, homeless guys sleeping in the sand dunes, and surfer dudes waiting for the perfect wave.

Grover, Annabeth, and I walked down to the edge of the surf.

"What now?" Annabeth asked.

The Pacific was turning gold in the setting sun. I thought about how long it had been since I'd stood on the beach at Montauk, on the opposite side of the country, looking out at a different sea.

How could there be a god who could control all that? What did my science teacher used to say—two-thirds of the earth's surface was covered in water? How could I be the son of someone that powerful?

I stepped into the surf.

"Percy?" Annabeth said. "What are you doing?"

I kept walking, up to my waist, then my chest.

She called after me, "You know how polluted that water is? There're all kinds of toxic—"

That's when my head went under.

I held my breath at first. It's difficult to intentionally inhale water. Finally I couldn't stand it anymore. I gasped. Sure enough, I could breathe normally.

I walked down into the shoals. I shouldn't have been able to see through the murk, but somehow I could tell where everything was. I could sense the rolling texture of the bottom. I could make out sand-dollar colonies dotting the sandbars. I could even see the currents, warm and cold streams swirling together.

I felt something rub against my leg. I looked down and almost shot out of the water like a ballistic missile. Sliding along beside me was a five-foot-long mako shark.

But the thing wasn't attacking. It was nuzzling me. Heeling like a dog. Tentatively, I touched its dorsal fin. It bucked a little, as if inviting me to hold tighter. I grabbed the fin with both hands. It took off, pulling me along. The shark carried me down into the darkness. It deposited me at the edge of the ocean proper, where the sand bank dropped off into a huge chasm. It was like standing on the rim of the Grand Canyon at midnight, not being able to see much, but knowing the void was right there.

The surface shimmered maybe a hundred and fifty feet above. I knew I should've been crushed by the pressure. Then again, I shouldn't have been able to breathe. I wondered if there was a limit to how deep I could go, if I could sink straight to the bottom of the Pacific.

Then I saw something glimmering in the darkness below, growing bigger and brighter as it rose toward me. A woman's voice, like my mother's, called: "Percy Jackson."

As she got closer, her shape became clearer. She had flowing black hair, a dress made of green silk. Light flickered around her, and her eyes were so distractingly beautiful I hardly noticed the stallion-sized sea horse she was riding.

She dismounted. The sea horse and the mako shark whisked off and started playing something that looked like tag. The underwater lady smiled at me. "You've come far, Percy Jackson. Well done."

I wasn't quite sure what to do, so I bowed. "You're the woman who spoke to me in the Mississippi River."

"Yes, child. I am a Nereid, a spirit of the sea. It was not easy to appear so far upriver, but the naiads, my freshwater cousins, helped sustain my life force. They honor Lord Poseidon, though they do not serve in his court."

"And ... you serve in Poseidon's court?"

She nodded. "It has been many years since a child of the Sea God has been born. We have watched you with great interest."

Suddenly I remembered faces in the waves off MontaukBeach when I was a little boy, reflections of smiling women. Like so many of the weird things in my life, I'd never given it much thought before.

"If my father is so interested in me," I said, "why isn't he here? Why doesn't he speak to me?"

A cold current rose out of the depths.

"Do not judge the Lord of the Sea too harshly," the Nereid told me. "He stands at the brink of an unwanted war. He has much to occupy his time. Besides, he is forbidden to help you directly. The gods may not show such favoritism."

"Even to their own children?"

"Especially to them. The gods can work by indirect influence only. That is why I give you a warning, and a gift."

She held out her hand. Three white pearls flashed in her palm.

"I know you journey to Hades's realm," she said. "Few mortals have ever done this and survived: Orpheus, who had great music skill; Hercules, who had great strength; Houdini, who could escape even the depths of Tartarus. Do you have these talents?"

"Urn ... no, ma'am."

"Ah, but you have something else, Percy. You have gifts you have only begun to know. The oracles have foretold a great and terrible future for you, should you survive to manhood. Poseidon would not have you die before your time. Therefore take these, and when you are in need, smash a pearl at your feet."

"What will happen?"

"That," she said, "depends on the need. But remember: what belongs to the sea will always return to the sea."

"What about the warning?"

Her eyes flickered with green light. "Go with what your heart tells you, or you will lose all. Hades feeds on doubt and hopelessness. He will trick you if he can, make you mistrust your own judgment. Once you are in his realm, he will never willingly let you leave. Keep faith. Good luck, Percy Jackson."

She summoned her sea horse and rode toward the void.

"Wait!" I called. "At the river, you said not to trust the gifts. What gifts?"

"Good-bye, young hero," she called back, her voice fading into the depths. "You must listen to your heart." She became a speck of glowing green, and then she was gone.

I wanted to follow her down into the darkness. I wanted to see the court of Poseidon. But I looked up at the sunset darkening on the surface. My friends were waiting. We had so little time....

I kicked upward toward the shore.

When I reached the beach, my clothes dried instantly. I told Grover and Annabeth what had happened, and showed them the pearls.

Annabeth grimaced. "No gift comes without a price."

"They were free."

"No." She shook her head. "'There is no such thing as a free lunch.' That's an ancient Greek saying that translated pretty well into American. There will be a price. You wait."

On that happy thought, we turned our backs on the sea.

With some spare change from Ares's backpack, we took the bus into West Hollywood. I showed the driver the Underworld address slip I'd taken from Aunty Em's Garden Gnome Emporium, but he'd never heard of DOA Recording Studios.