If you want to be popular at Camp Half-Blood, don't come back from a mission with bad news.

Word of my arrival spread as soon as I walked out of the ocean. Our beach is on the North Shore of Long Island, and it's enchanted so most people can't even see it. People don't just appear on the beach unless they're demigods or gods or really, really lost pizza delivery guys. (It's happened—but that's another story.)

Anyway, that afternoon the lookout on duty was Connor Stoll from the Hermes cabin. When he spotted me, he got so excited he fell out of his tree. Then he blew the conch horn to signal the camp and ran to greet me.

Connor had a crooked smile that matched his crooked sense of humor. He's a pretty nice guy, but you should always keep one hand on your wallet when he's around, and do not, under any circumstances, give him access to shaving cream unless you want to find your sleeping bag full of it. He's got curly brown hair and is a little shorter than his brother, Travis, which is the only way I can tell them apart. They are both so unlike my old enemy Luke it's hard to believe they're all sons of Hermes.

"Percy!" he yelled. "What happened? Where's Beckendorf?"

Then he saw my expression, and his smile melted. "Oh, no. Poor Silena. Holy Zeus, when she finds out . . ."

Together we climbed the sand dunes. A few hundred yards away, people were already streaming toward us, smiling and excited. Percy's back, they were probably thinking. He's saved the day! Maybe he brought souvenirs!

I stopped at the dining pavilion and waited for them. No sense rushing down there to tell them what a loser I was.

I gazed across the valley and tried to remember how Camp Half-Blood looked the first time I ever saw it. That seemed like a bajillion years ago.

From the dining pavilion, you could see pretty much everything. Hills ringed the valley. On the tallest, Half-Blood Hill, Thalia's pine tree stood with the Golden Fleece hanging from its branches, magically protecting the camp from its enemies. The guard dragon Peleus was so big now I could see him from here—curled around the tree trunk, lending up smoke signals as he snored.

To my right spread the woods. To my left, the canoe lake glittered and the climbing wall glowed from the lava pouring down its side. Twelve cabins—one for each Olympian god—made a horseshoe pattern around the commons area. Farther south were the strawberry fields, the armory, and the four-story Big House with its sky blue paint job and its bronze eagle weathervane.

In some ways, the camp hadn't changed. But you couldn't see the war by looking at the buildings or the fields. You could see it in the faces of the demigods and satyrs and naiads coming up the hill.

There weren't as many at camp as four summers ago. Some had left and never come back. Some had died fighting. Others—we tried not to talk about them—had gone over to the enemy.

The ones who were still here were battle-hardened and weary. There was little laughter at camp these days. Even the Hermes cabin didn't play so many pranks. It's hard to enjoy practical jokes when your whole life feels like one.

Chiron galloped into the pavilion first, which was easy for him since he's a white stallion from the waist down. His beard had grown wilder over the summer. He wore a green T-shirt that said MY OTHER CAR IS A CENTAUR and a bow slung over his back.

"Percy!" he said. "Thank the gods. But where . . ."

Annabeth ran in right behind him, and I'll admit my heart did a little relay race in my chest when I saw her. It's not that she tried to look good. We'd been doing so many combat missions lately, she hardly brushed her curly blond hair anymore, and she didn't care what clothes she was wearing—usually the same old orange camp T-shirt and jeans, and once in a while her bronze armor. Her eyes were stormy gray. Most of the time we couldn't get through a conversation without trying to strangle each other. Still, just seeing her made me feel fuzzy in the head. Last summer, before Luke had turned into Kronos and everything went sour, there had been a few times when I thought maybe . . . well, that we might get past the strangle-each-other phase.

"What happened?" She grabbed my arm. "Is Luke—"

"The ship blew up," I said. "He wasn't destroyed. I don't know where—"

Silena Beauregard pushed through the crowd. Her hair wasn't combed and she wasn't even wearing makeup, which wasn't like her.

"Where's Charlie?" she demanded, looking around like he might be hiding.

I glanced at Chiron helplessly.

The old centaur cleared his throat. "Silena, my dear, let's talk about this at the Big House—"

"No," she muttered. "No. No."

She started to cry, and the rest of us stood around, too stunned to speak. We'd already lost so many people over the summer, but this was the worst. With Beckendorf gone, it felt like someone had stolen the anchor for the entire camp.

Finally Clarisse from the Ares cabin came forward. She put her arm around Silena. They had one of the strangest friendships ever—a daughter of the war god and a daughter of the love goddess—but ever since Silena had given Clarisse advice last summer about her first boyfriend, Clarisse had decided she was Silena's personal bodyguard.

Clarisse was dressed in her bloodred combat armor, her brown hair tucked into a bandana. She was as big and beefy as a rugby player, with a permanent scowl on her face, but she spoke gently to Silena.

"Come on, girl," she said. "Let's get to the Big House. I'll make you some hot chocolate."

Everyone turned and wandered off in twos and threes, heading back to the cabins. Nobody was excited to see me now. Nobody wanted to hear about the blown-up ship.

Only Annabeth and Chiron stayed behind.

Annabeth wiped a tear from her cheek. "I'm glad you're not dead, Seaweed Brain."

"Thanks," I said. "Me too."

Chiron put a hand on my shoulder. "I'm sure you did everything you could, Percy. Will you tell us what happened?"

I didn't want to go through it again, but I told them the story, including my dream about the Titans. I left out the detail about Nico. Nico had made me promise not to tell anybody about his plan until I made up my mind, and the plan was so scary I didn't mind keeping it a secret.

Chiron gazed down at the valley. "We must call a war council immediately, to discuss this spy, and other matters."

"Poseidon mentioned another threat," I said. "Something even bigger than the Princess Andromeda. I thought it might be that challenge the Titan had mentioned in my dream."

Chiron and Annabeth exchanged looks, like they knew something I didn't. I hated when they did that.

"We will discuss that also," Chiron promised.

"One more thing." I took a deep breath. "When I talked to my father, he said to tell you it's time. I need to know the full prophecy."

Chiron's shoulders sagged, but he didn't look surprised. "I've dreaded this day. Very well. Annabeth, we will show Percy the truth—all of it. Let's go to the attic."

I’d been to the Big House attic three times before, which was three times more than I wanted to.

A ladder led up from the top of the staircase. I wondered how Chiron was going to get up there, being half horse and all, but he didn't try.

"You know where it is," he told Annabeth. "Bring it down, please."

Annabeth nodded. "Come on, Percy."

The sun was setting outside, so the attic was even darker and creepier than usual. Old hero trophies were slacked everywhere—dented shields, pickled heads in jars from various monsters, a pair of fuzzy dice on a bronze plaque that read: STOLEN FROM CHRYSAOR'S HONDA CIVIC, BY GUS, SON OF HERMES, 1988.