“What do you mean he just appeared?”

“He was wandering around the desert, in a hundred and twenty degrees, in full Greek armor, babbling about string.”

“String,” I said.

“He’d been driven completely insane. Clarisse brought him back to her mom’s house so the mortals wouldn’t institutionalize him. She tried to nurse him back to health. Chiron came out and interviewed him, but it wasn’t much good. The only thing they got out of him: Luke’s men have been exploring the Labyrinth.”

I shivered, though I wasn’t exactly sure why. Poor Chris…he hadn’t been a bad guy. What could’ve driven him mad? I looked at Grover, who was chewing up the rest of his fork.

“Okay,” I asked. “Why were they exploring the Labyrinth?”

“We weren’t sure,” Annabeth said. “That’s why Clarisse went on a scouting expedition. Chiron kept things hushed up because he didn’t want anyone panicking. He got me involved because…well, the Labyrinth has always been one of my favorite subjects. The architecture involved—” Her expression turned a little dreamy. “The builder, Daedalus, was a genius. But the point is, the Labyrinth has entrances everywhere. If Luke could figure out how to navigate it, he could move his army around with incredible speed.”

“Except it’s a maze, right?”

“Full of horrible traps,” Grover agreed. “Dead ends. Illusions. Psychotic goat-killing monsters.”

“But not if you had Ariadne’s string,” Annabeth said. “In the old days, Ariadne’s string guided Theseus out of the maze. It was a navigation instrument of some kind, invented by Daedalus. And Chris Rodriguez was mumbling about string.”

“So Luke is trying to find Ariadne’s string,” I said. “Why? What’s he planning?”

Annabeth shook her head. “I don’t know. I thought maybe he wanted to invade camp through the maze, but that doesn’t make any sense. The closest entrances Clarisse found were in Manhattan, which wouldn’t help Luke get past our borders. Clarisse explored a little way into the tunnels, but…it was very dangerous. She had some close calls. I researched everything I could find about Daedalus. I’m afraid it didn’t help much. I don’t understand exactly what Luke’s planning, but I do know this: the Labyrinth might be the key to Grover’s problem.”

I blinked. “You think Pan is underground?”

“It would explain why he’s been impossible to find.”

Grover shuddered. “Satyrs hate going underground. No searcher would ever try going in that place. No flowers. No sunshine. No coffee shops!”

“But,” Annabeth said, “the Labyrinth can lead you almost anywhere. It reads your thoughts. It was designed to fool you, trick you and kill you; but if you can make the Labyrinth work for you—”

“It could lead you to the wild god,” I said.

“I can’t do it.” Grover hugged his stomach. “Just thinking about it makes me want to throw up my silverware.”

“Grover, it may be your last chance,” Annabeth said. “The council is serious. One week or you learn to tap dance!”

Over at the head table, Quintus cleared his throat. I got the feeling he didn’t want to make a scene, but Annabeth was really pushing it, sitting at my table so long.

“We’ll talk later,” Annabeth squeezed my arm a little too hard. “Convince him, will you?”

She returned to the Athena table, ignoring all the people who were staring at her.

Grover buried his head in his hands. “I can’t do it, Percy. My searcher’s license. Pan. I’m going to lose it all. I’ll have to start a puppet theater.”

“Don’t say that! We’ll figure something out.”

He looked at me teary-eyed. “Percy, you’re my best friend. You’ve seen me underground. In that Cyclops’s cave. Do you really think I could…”

His voice faltered. I remembered the Sea of Monsters, when he’d been stuck in a Cyclops’s cave. He’d never liked underground places to begin with, but now Grover really hated them. Cyclopes gave him the creeps, too. Even Tyson…Grover tried to hide it, but Grover and I could sort of read each other’s emotions because of this empathy link between us. I knew how he felt. Grover was terrified of the big guy.

“I have to leave,” Grover said miserably. “Juniper’s waiting for me. It’s a good thing she finds cowards attractive.”

After he was gone, I looked over at Quintus. He nodded gravely, like we were sharing some dark secret. Then he went back to cutting his sausage with a dagger.

In the afternoon, I went down to the Pegasus stables to visit my friend Blackjack.

Yo, boss! He capered around in his stall, his black wings buffeting the air. Ya bring me some sugar cubes?

“You know those aren’t good for you, Blackjack.”

Yeah, so you brought me some, huh?

I smiled and fed him a handful. Blackjack and I went back a long way. I sort of helped rescue him from Luke’s demon cruise ship a few years ago, and ever since, he insisted on repaying me with favors.

So we got any quests coming up? Blackjack asked. I’m ready to fly, boss!

I patted his nose. “Not sure, man. Everybody keeps talking about underground mazes.”

Blackjack whinnied nervously. Nuh-uh. Not for this horse! You aint gonna be crazy enough to go in no maze, boss. Are ya? You’ll end up in the glue factory!

“You may be right, Blackjack. We’ll see.”

Blackjack crunched down his sugar cubes. He shook his mane like he was having a sugar seizure. Whoa! Good stuff! Well, boss, you come to your senses and want to fly somewhere, just give a whistle. Ole Blackjack and his buddies, we’ll stampede anybody for ya!

I told him I’d keep it in mind. Then a group of younger campers came into the stables to start their riding lessons, and I decided it was time to leave. I had a bad feeling I wasn’t going to see Blackjack for a long time.

That night after dinner, Quintus had us suit up in combat armor like we were getting ready for capture the flag, but the mood among the campers was a lot more serious. Sometime during the day the crates in the arena had disappeared, and I had a feeling whatever was in them had been emptied into the woods.

“Right,” Quintus said, standing on the head dining table. “Gather ’round.”

He was dressed in black leather and bronze. In the torchlight, his gray hair made him look like a ghost. Mrs. O’Leary bounded happily around him, foraging for dinner scraps.

“You will be in teams of two,” Quintus announced. When everybody started talking and trying to grab their friends, he yelled: “Which have already been chosen!”

“AWWWWW!” everybody complained.

“Your goal is simple: collect the gold laurels without dying. The wreath is wrapped in a silk package, tied to the back of one of the monsters. There are six monsters. Each has a silk package. Only one holds the laurels. You must find the wreath before the other teams. And, of course…you will have to slay the monster to get it, and stay alive.”

The crowd started murmuring excitedly. The task sounded pretty straightforward. Hey, we’d all slain monsters before. That’s what we trained for.

“I will now announce your partners,” Quintus said. “There will be no trading. No switching. No complaining.”

“Aroooof!” Mrs. O’Leary buried her face in a plate of pizza.

Quintus produced a big scroll and started reading off names. Beckendorf would be with Silena Beauregard, which Beckendorf looked pretty happy about. The Stoll brothers, Travis and Connor, would be together. No surprise. They did everything together. Clarisse was with Lee Fletcher from the Apollo cabin—melee and ranged combat combined, they would be a tough combo to beat. Quintus kept rattling off the names until he said, “Percy Jackson with Annabeth Chase.”

“Nice.” I grinned at Annabeth.

“Your armor is crooked” was her only comment, and she redid my straps for me.

“Grover Underwood,” Quintus said, “with Tyson.”

Grover just about jumped out of his goat fur. “What? B-but—”

“No, no,” Tyson whimpered. “Must be a mistake. Goat boy—”

“No complaining!” Quintus ordered. “Get with your partner. You have two minutes to prepare!”

Tyson and Grover both looked at me pleadingly. I tried to give them an encouraging nod, and gestured that they should move together. Tyson sneezed. Grover started chewing nervously on his wooden club.

“They’ll be fine,” Annabeth said. “Come on. Let’s worry about how we’re going to stay alive.”

It was still light when we got into the woods, but the shadows from the trees made it feel like midnight. It was cold, too, even in summer. Annabeth and I found tracks almost immediately—scuttling marks made by something with a lot of legs. We began to follow the trail.

We jumped a creek and heard some twigs snapping nearby. We crouched behind a boulder, but it was only the Stoll brothers tripping through the woods and cursing. Their dad was the god of thieves, but they were about as stealthy as buffaloes.

Once the Stolls had passed, we forged deeper into the west woods where the monsters were wilder. We were standing on a ledge overlooking a marshy pond when Annabeth tensed. “This is where we stopped looking.”

It took me a second to realize what she meant. Last winter, when we’d given up hope of finding him, Grover, Annabeth, and I had stood on this rock, and I’d convinced them not to tell Chiron the truth: that Nico was a son of Hades. At the time it seemed the right thing to do. I wanted to protect his identity. I wanted to be the one to find him and make things right for what had happened to his sister. Now, six months later, I hadn’t even come close to finding him. It left a bitter taste in my mouth.

“I saw him last night,” I said.

Annabeth knit her eyebrows. “What do you mean?”

I told her about the Iris-message. When I was done, she stared into the shadows of the woods. “He’s summoning the dead? That’s not good.”

“The ghost was giving him bad advice,” I said. “Telling him to take revenge.”

“Yeah…spirits are never good advisers they’ve got their own agendas. Old grudges. And they resent the living.”

“He’s going to come after me,” I said. “The spirit mentioned a maze.”

She nodded. “That settles it. We have to figure out the Labyrinth.”

“Maybe,” I said uncomfortably. “But who sent the Iris-message? If Nico didn’t know I was there—”

A branch snapped in the woods. Dry leaves rustled. Something large was moving in the trees, just beyond the ridge.

“That’s not the Stoll brothers,” Annabeth whispered.

Together we drew our swords.

We got to Zeus’s Fist, a huge pile of boulders in the middle of the west woods. It was a natural landmark where campers often rendezvoused on hunting expeditions, but now there was nobody around.