When it stood again, I could see it much more clearly—a teenage guy in Greek armor. He had curly hair and green eyes, a clasp shaped like a seashell on his cloak.

“Who are you?” Nico said. “Speak.”

The young man frowned as if trying to remember. Then he spoke in a voice like dry, crumpling paper: “I am Theseus.”

No way, I thought. This couldn’t be the Theseus. He was just a kid. I’d grown up hearing stories about him fighting the Minotaur and stuff, but I’d always pictured him as this huge, buff guy. The ghost I was looking at wasn’t strong or tall. And he wasn’t any older than I was.

“How can I retrieve my sister?” Nico asked.

Theseus’s eyes were lifeless as glass. “Do not try. It is madness.”

“Just tell me!”

“My stepfather died,” Theseus remembered. “He threw himself into the sea because he thought I was dead in the Labyrinth. I wanted to bring him back, but I could not.”

Nico’s ghost hissed. “My lord, the soul exchange! Ask him about that!”

Theseus scowled. “That voice. I know that voice.”

“No you don’t, fool!” the ghost said. “Answer the lord’s questions and nothing more!”

“I know you,” Theseus insisted, as if struggling to recall.

“I want to hear about my sister,” Nico said. “Will this quest into the Labyrinth help me win her back?”

Theseus was looking for the ghost, but apparently couldn’t see him. Slowly he turned his eyes back on Nico. “The Labyrinth is treacherous. There is only one thing that saw me through: the love of a mortal girl. The string was only part of the answer. It was the princess who guided me.”

“We don’t need any of that,” the ghost said. “I will guide you, my lord.

Ask him if it is true about an exchange of souls. He will tell you.”

“A soul for a soul,” Nico asked. “Is it true?”

“I—I must say yes. But the specter—”

“Just answer the questions, knave!” the ghost said.

Suddenly, around the edges of the pool, the other ghosts became restless.

They stirred, whispering in nervous tones.

“I want to see my sister!” Nico demanded. “Where is she?”

“He is coming,” Theseus said fearfully. “He has sensed your summons. He comes.”

“Who?” Nico demanded.

“He comes to find the source of this power,” Theseus said. “You must release us.”

The water in my fountain began to tremble, humming with power. I realized the whole cabin was shaking. The noise grew louder. The image of Nico in the graveyard started to glow until it was painful to watch.

“Stop,” I said out loud. “Stop it!”

The fountain began to crack. Tyson muttered in his sleep and turned over. Purple light threw horrible, ghostly shadows on the cabin walls, as if the specters were escaping right out of the fountain.

In desperation I uncapped riptide and slashed at the fountain, cleaving it in two. Salt water spilled everywhere, and the great stone font crashed to the floor in pieces. Tyson snorted and muttered, but he kept sleeping.

I sank to the ground, shivering from what I’d seen. Tyson found me there in the morning, still staring at the shattered remains of the saltwater fountain.

***

Just after dawn, the quest group met at Zeus’s Fist. I’d packed my knapsack—thermos with nectar, baggie of ambrosia, bedroll, rope, clothes, flashlights, and lots of extra batteries. I had Riptide in my pocket. The magic shield/wristwatch Tyson had made for me was on my wrist.

It was a clear morning. The fog had burned off and the sky was blue. Campers would be having their lessons today, flying pegasi and practicing archery and scaling the lava wall. Meanwhile, we could be heading underground.

Juniper and Grover stood apart from the group. Juniper had been crying again, but she was trying to keep it together for Grover’s sake. She kept fussing with his clothes, straightening his rasta cap and brushing goat fur off his shirt. Since we had no idea what we would encounter, he was dressed as a human, with the cap to hide his horns, and jeans, fake feet, and sneakers to hide his goat legs.

Chiron, Quintus, and Mrs. O’Leary stood with the other campers who’d come to wish us well, but there was too much activity for it to feel like a happy send-off. A couple of tents had been set up by the rocks for guard duty. Beckendorf and his siblings were working on a line of defensive spikes and trenches. Chiron had decided we needed to guard the Labyrinth exit at all times, just in case.

Annabeth was doing one last check on her supply pack. When Tyson and I came over, she frowned. “Percy, you look terrible.”

“He killed the water fountain last night,” Tyson confided.

“What?” she asked.

Before I could explain, Chiron trotted over. “Well, it appears you are ready!”

He tried to sound upbeat, but I could tell he was anxious. I didn’t want to freak him out any more, but I thought about last night’s dream, and before I could change my mind, I said, “Hey, uh, Chiron, can I ask you a favor while I’m gone?”

“Of course, my boy.”

“Be right back, guys.” I nodded toward the woods. Chiron asked an eyebrow, but he followed me out of earshot.

“Last night,” I said, “I dreamed about Luke and Kronos.” I told him the details. The news seemed to weigh on his shoulders.

“I feared this,” Chiron said. “Against my father, Kronos, we would stand no chance in a fight.”

Chiron rarely called Kronos his father. I mean, we all knew it was true. Everybody in the Greek world—god, monster, or Titan—was related to one another somehow. But it wasn’t exactly something Chiron liked to brag about. Oh, my dad is the all-powerful evil Titan lord who wants to destroy Western Civilization. I want to be just like him when I grow up!

“Do you know what he meant about a bargain?” I asked.

“I am not sure, but I fear they seek to make a deal with Daedalus. If the old inventor is truly alive, if he has not been driven insane by millennia in the Labyrinth…well, Kronos can find ways to twist anyone to his will.”

“Not anyone,” I promised.

Chiron managed a smile. “No. Perhaps not anyone. But, Percy, you must beware. I have worried for some time that Kronos may be looking for Daedalus for a different reason, not just passage through the maze.”

“What else would he want?”

“Something Annabeth and I were discussing. Do you remember what you told me about your first trip to the Princess Andromeda, the first time you saw the golden coffin?”

I nodded. “Luke was taking about raising Kronos, little pieces of him appearing in the coffin every time someone new joined his cause.”

“And what did Luke say they would do when Kronos had risen completely?”

A chill went down my spine. “He said they would make Kronos a new body, worthy of the forges of Hephaestus.”

“Indeed,” Chiron said. “Daedalus was the world’s greatest inventor. He created the Labyrinth, but much more. Automatons, thinking machines…What if Kronos wishes Daedalus to make him a new form?”

That was a real pleasant thought.

“We’ve got to get to Daedalus first,” I said, “and convince him not to.”

Chiron stared off into the trees. “One other thing I do not understand…this talk of a last soul joining their cause. That does not bode well.”

I kept my mouth shut, but I felt guilty. I’d made the decision not to tell Chiron about Nico being a son of Hades. The mention of souls, though— What if Kronos knew about Nico? What if he managed to turn him evil? It was almost enough to make me want to tell Chiron, but I didn’t. for one thing, I wasn’t sure Chiron could do anything about it. I had to find Nico myself. I had to explain things to him, make him listen.

“I don’t know,” I said at last. “But, uh, something Juniper said, maybe you should hear.” I told him how the tree nymph had seen Quintus poking around the rocks.

Chiron’s jaw tightened. “That does not surprise me.”

“It doesn’t sur—you mean you know?”

“Percy, when Quintus showed up at camp offering his services…well, I would have to be a fool not to be suspicious.”

“Then why did you let him in?”

“Because sometimes it is better to have someone you mistrust close to you, so that you can keep an eye on him. He may be just what he says: a half-blood in search of a home. Certainly he has done nothing openly that would make me question his loyalty. But believe me. I will keep an eye—”

Annabeth trudged over, probably curious why we were taking so long.

“Percy, you ready?”

I nodded. My hand slipped into my pocket, where I kept the ice whistle Quintus had given me. I looked over and saw Quintus watching me carefully. He raised his hand in farewell.

Our spies report success, Luke had said. The same day we decided to send a quest, Luke had known about it.

“Take care,” Chiron told us. “And good hunting.”

“You too,” I said.

We walked over to the rocks, where Tyson and Grover were waiting. I stared at the crack between the boulders—the entrance that was about to swallow us.

“Well,” Grover said nervously, “good-bye sunshine.”

“Hello rocks,” Tyson agreed. And together, the four of us descended into darkness.

SIX

WE MEET THE GOD WITH TWO FACES

We made it a hundred feet before we were hopelessly lost.

The tunnel looked nothing like the one Annabeth and I had stumbled into before. Now it was round like a sewer, constructed of red brick with iron-barred portholes ever ten feet. I shined a light through one of the portholes out of curiosity, but I couldn’t see anything. It opened into infinite darkness. I thought I heard voices on the other side, but it may have been just the cold wind.

Annabeth tried her best to guide us. She had this idea that we should stick to the left wall.

“If we keep one hand on the left wall and follow it,” she said, “we should be able to find our way out again by reversing course.”

Unfortunately, as soon as she said that, the left wall disappeared. We found ourselves in the middle of a circular chamber with eight tunnels leading out, and no idea how we’d gotten there.

“Um, which way did we come in?” Grover said nervously.

“Just turn around,” Annabeth said.

We each turned toward a different tunnel. It was ridiculous. None of us could decide which way led back to camp.

“Left walls are mean,” Tyson said. “Which way now?”

Annabeth swept her flashlight beam over the archways of the eight tunnels. As far as I could tell, they were identical. “That way,” she said.

“How do you know?” I asked.

“Deductive reasoning.”

“So…you’re guessing.”

“Just come on,” she said.

The tunnel she’d chosen narrowed quickly. The walls turned to gray cement, and the ceiling got so low that pretty soon we were hunching over. Tyson was forced to crawl.