"Trust me," I said. "I'll see you there."

I hung up. My hands were trembling. I wasn't sure if it was a leftover reaction from my dip in the Styx, or anticipation of what I was about to do. If this didn't work, being invulnerable wasn't going to save me from getting blasted to bits.

It was late afternoon when the taxi dropped me at the Empire State Building. Mrs. O'Leary bounded up and down Fifth Avenue, licking cabs and sniffing hot dog carts. Nobody seemed to notice her, although people did swerve away and look confused when she came close.

I whistled for her to heel as three white vans pulled up to the curb. They said Delphi Strawberry Service, which was the cover name for Camp Half-Blood. I'd never seen all three vans in the same place at once, though I knew they shuttled our fresh produce into the city.

The first van was driven by Argus, our many-eyed security chief. The other two were driven by harpies, who are basically demonic human/chicken hybrids with bad attitudes. We used the harpies mostly for cleaning the camp, but they did pretty well in midtown traffic too.

The doors slid open. A bunch of campers climbed out, some of them looking a little green from the long drive. I was glad so many had come: Pollux, Silena Beauregard, the Stoll brothers, Michael Yew, Jake Mason, Katie Gardner, and Annabeth, along with most of their siblings. Chiron came out of the van last. His horse half was compacted into his magic wheelchair, so he used the handicap lift. The Ares cabin wasn't here, but I tried not to get too angry about that. Clarisse was a stubborn idiot. End of story.

I did a head count: forty campers in all.

Not many to fight a war, but it was still the largest group of half-bloods I'd ever seen gathered in one place outside camp. Everyone looked nervous, and I understood why. We were probably sending out so much demigod aura that every monster in the northeastern United States knew we were here.

As I looked at their faces—all these campers I'd known for so many summers—a nagging voice whispered in my mind: One of them is a spy.

But I couldn't dwell on that. They were my friends. I needed them.

Then I remembered Kronos's evil smile. You can't count on friends. They will always let you down.

Annabeth came up to me. She was dressed in black camouflage with her Celestial bronze knife strapped to her arm and her laptop bag slung over her shoulder—ready for stabbing or surfing the Internet, whichever came first.

She frowned. "What is it?"

"What's what?" I asked.

"You're looking at me funny."

I realized I was thinking about my strange vision of Annabeth pulling me out of the Styx River. "It's, uh, nothing." I turned to the rest of the group. "Thanks for coming, everybody. Chiron, after you."

My old mentor shook his head. "I came to wish you luck, my boy. But I make it a point never to visit Olympus unless I am summoned."

"But you're our leader."

He smiled. "I am your trainer, your teacher. That is not the same as being your leader. I will go gather what allies I can. It may not be too late to convince my brother centaurs to help. Meanwhile, you called the campers here, Percy. You are the leader."

I wanted to protest, but everybody was looking at me expectantly, even Annabeth.

I took a deep breath. "Okay, like I told Annabeth on the phone, something bad is going to happen by tonight. Some kind of trap. We've got to get an audience with Zeus and convince him to defend the city. Remember, we can't take no for an answer."

I asked Argus to watch Mrs. O'Leary, which neither of them looked happy about.

Chiron shook my hand. "You'll do well, Percy. Just remember your strengths and beware your weaknesses."

It sounded eerily close to what Achilles had told me. Then I remembered Chiron had taught Achilles. That didn't exactly reassure me, but I nodded and tried to give him a confident smile.

"Let's go," I told the campers.

A security guard was sitting behind the desk in the lobby, reading a big black book with a flower on the cover. He glanced up when we all filed in with our weapons and armor clanking. "School group? We're about to close up."

"No," I said. "Six-hundredth floor."

He checked us out. His eyes were pale blue and his head was completely bald. I couldn't tell if he was human or not, but he seemed to notice our weapons, so I guess he wasn't fooled by the Mist.

"There is no six-hundredth floor, kid." He said it like it was a required line he didn't believe. "Move along."

I leaned across the desk. "Forty demigods attract an awful lot of monsters. You really want us hanging out in your lobby?"

He thought about that. Then he hit a buzzer and the security gate swung open. "Make it quick."

"You don't want us going through the metal detectors," I added.

"Um, no," he agreed. "Elevator on the right. I guess you know the way."

I tossed him a golden drachma and we marched ill rough.

We decided it would take two trips to get everybody up in the elevator. I went with the first group. Different elevator music was playing since my last visit—that old disco song "Stayin' Alive." A terrifying image flashed through my mind of Apollo in bell-bottom pants and a slinky silk shirt.

I was glad when the elevator doors finally dinged open. In front of us, a path of floating stones led through the clouds up to Mount Olympus, hovering six thousand feet over Manhattan.

I'd seen Olympus several times, but it still took my breath away. The mansions glittered gold and white against the sides of the mountain. Gardens bloomed on a hundred terraces. Scented smoke rose from braziers that lined the winding streets. And right at the top of the snow-capped crest rose the main palace of the gods. It looked as majestic as ever, but something seemed wrong. Then I realized the mountain was silent—no music, no voices, no laughter.

Annabeth studied me. "You look . . . different," she decided. "Where exactly did you go?"

The elevator doors opened again, and the second group of half-bloods joined us.

"Tell you later," I said. "Come on."

We made our way across the sky bridge into the streets of Olympus. The shops were closed. The parks were empty. A couple of Muses sat on a bench strumming flaming lyres, but their hearts didn't seem to be in it. A lone Cyclops swept the street with an uprooted oak tree. A minor godling spotted us from a balcony and ducked inside, closing his shutters.

We passed under a big marble archway with statues of Zeus and Hera on either side. Annabeth made a face at the queen of the gods.

"Hate her," she muttered.

"Has she been cursing you or something?" I asked. Last year Annabeth had gotten on Hera's bad side, but Annabeth hadn't really talked about it since.

"Just little stuff so far," she said. "Her sacred animal is the cow, right?"

"Right."

"So she sends cows after me."

I tried not to smile. "Cows? In San Francisco?"

"Oh, yeah. Usually I don't see them, but the cows leave me little presents all over the place—in our backyard, on the sidewalk, in the school hallways. I have to be careful where I step."

"Look!" Pollux cried, pointing toward the horizon. "What is that?"

We all froze. Blue lights were streaking across the evening sky toward Olympus like tiny comets. They seemed to be coming from all over the city, heading straight toward the mountain. As they got close, they fizzled out. We watched them for several minutes and they didn't seem to do any damage, but still it was strange.

"Like infrared scopes," Michael Yew muttered. "We're being targeted."

"Let's get to the palace," I said.

No one was guarding the hall of the gods. The gold-and-silver doors stood wide open. Our footsteps echoed as we walked into the throne room.