Of course, "room" doesn't really cover it. The place was the size of Madison Square Garden. High above, the blue ceiling glittered with constellations. Twelve giant empty thrones stood in a U around a hearth. In one corner, a house-size globe of water hovered in the air, and inside swam my old friend the Ophiotaurus, half-cow, half-serpent.

"Moooo!" he said happily, turning in a circle.

Despite all the serious stuff going on, I had to smile. Two years ago we'd spent a lot of time trying to save the Ophiotaurus from the Titans, and I'd gotten kind of fond of him. He seemed to like me too, even though I'd originally thought he was a girl and named him Bessie.

"Hey, man," I said. "They treating you okay?"

"Mooo," Bessie answered.

We walked toward the thrones, and a woman's voice said, "Hello again, Percy Jackson. You and your friends are welcome."

Hestia stood by the hearth, poking the flames with a stick. She wore the same kind of simple brown dress as she had before, but she was a grown woman now.

I bowed. "Lady Hestia."

My friends followed my example.

Hestia regarded me with her red glowing eyes. "I see you went through with your plan. You bear the curse of Achilles."

The other campers started muttering among themselves: What did she say? What about Achilles?

"You must be careful," Hestia warned me. "You gained much on your journey. But you are still blind to the most important truth. Perhaps a glimpse is in order."

Annabeth nudged me. "Um . . . what is she talking about?"

I stared into Hestia's eyes, and an image rushed into my mind: I saw a dark alley between red brick warehouses. A sign above one of the doors read RICHMOND IRONWORKS.

Two half-bloods crouched in the shadows—a boy about fourteen and a girl about twelve. I realized with a start that the boy was Luke. The girl was Thalia, daughter of Zeus. I was seeing a scene from back in the days when they were on the run, before Grover found them.

Luke carried a bronze knife. Thalia had her spear and shield of terror, Aegis. Luke and Thalia both looked hungry and lean, with wild animal eyes, like they were used to being attacked.

"Are you sure?" Thalia asked.

Luke nodded. "Something down here. I sense it."

A rumble echoed from the alley, like someone had banged on a sheet of metal. The half-bloods crept forward.

Old crates were stacked on a loading dock. Thalia and Luke approached with their weapons ready. A curtain of corrugated tin quivered as if something were behind it.

Thalia glanced at Luke. He counted silently: One, two, three! He ripped away the tin, and a little girl flew at him with a hammer.

"Whoa!" Luke said.

The girl had tangled blond hair and was wearing flannel pajamas. She couldn't have been more than seven, but she would've brained Luke if he hadn't been so fast.

He grabbed her wrist, and the hammer skittered across the cement.

The little girl fought and kicked. "No more monsters! Go away!"

"It's okay!" Luke struggled to hold her. "Thalia, put your shield up. You're scaring her."

Thalia tapped Aegis, and it shrank into a silver bracelet. "Hey, it's all right," she said. "We're not going to hurt you. I'm Thalia. This is Luke."

"Monsters!"

"No," Luke promised. "But we know all about monsters. We fight them too."

Slowly, the girl stopped kicking. She studied Luke and Thalia with large intelligent gray eyes.

"You're like me?" she said suspiciously.

"Yeah," Luke said. "We're . . . well, it's hard to explain, but we're monster fighters. Where's your family?"

"My family hates me," the girl said. "They don't want me. I ran away."

Thalia and Luke locked eyes. I knew they both related to what she was saying.

"What's your name, kiddo?" Thalia asked.

"Annabeth."

Luke smiled. "Nice name. I tell you what, Annabeth—you're pretty fierce. We could use a fighter like you."

Annabeth's eyes widened. "You could?"

"Oh, yeah." Luke turned his knife and offered her the handle. "How'd you like a real monster-slaying weapon? This is Celestial bronze. Works a lot better than a hammer."

Maybe under most circumstances, offering a seven-year-old kid a knife would not be a good idea, but when you're a half-blood, regular rules kind of go out the window.

Annabeth gripped the hilt.

"Knives are only for the bravest and quickest fighters," Luke explained. "They don't have the reach or power of a sword, but they're easy to conceal and they can find weak spots in your enemy's armor. It takes a clever warrior to use a knife. I have a feeling you're pretty clever."

Annabeth stared at him with adoration. "I am!"

Thalia grinned. "We'd better get going, Annabeth. We have a safe house on the James River. We'll get you some clothes and food."

"You're . . . you're not going to take me back to my family?" she said. "Promise?"

Luke put his hand on her shoulder. "You're part of our family now. And I promise I won't let anything hurt you. I'm not going to fail you like our families did us. Deal?"

"Deal!" Annabeth said happily.

"Now, come on," Thalia said. "We can't stay put for long!"

The scene shifted. The three demigods were running through the woods. It must've been several days later, maybe even weeks. All of them looked beat up, like they'd seen some battles. Annabeth was wearing new clothes—jeans and an oversize army jacket.

"Just a little farther!" Luke promised. Annabeth stumbled, and he took her hand. Thalia brought up the rear, brandishing her shield like she was driving back whatever pursued them. She was limping on her left leg.

They scrambled to a ridge and looked down the other side at a white Colonial house—May Castellan's place.

"All right," Luke said, breathing hard. "I'll just sneak in and grab some food and medicine. Wait here."

"Luke, are you sure?" Thalia asked. "You swore you'd never come back here. If she catches you—"

"We don't have a choice!" he growled. "They burned our nearest safe house. And you've got to treat that leg wound."

"This is your house?" Annabeth said with amazement.

"It was my house," Luke muttered. "Believe me, if it wasn't an emergency—"

"Is your mom really horrible?" Annabeth asked. "Can we see her?"

"No!" Luke snapped.

Annabeth shrank away from him as though his anger surprised her.

"I . . . I'm sorry," he said. "Just wait here. I promise everything will be okay. Nothing's going to hurt you. I'll be back—"

A brilliant golden flash illuminated the woods. The demigods winced, and a man's voice boomed: "You should not have come home."

The vision shut off.

My knees buckled, but Annabeth grabbed me. "Percy! What happened?"

"Did . . . did you see that?" I asked.

"See what?"

I glanced at Hestia, but the goddess's face was expressionless. I remembered something she'd told me in the woods: If you are to understand your enemy Luke, you must understand his family. But why had she shown me those scenes?

"How long was I out?" I muttered.

Annabeth knit her eyebrows. "Percy, you weren't out at all. You just looked at Hestia for like one second and collapsed."

I could feel everyone's eyes on me. I couldn't afford to look weak. Whatever those visions meant, I had to stay focused on our mission.

"Um, Lady Hestia," I said, "we've come on urgent business. We need to see—"

"We know what you need," a man's voice said. I shuddered, because it was the same voice I'd heard in the vision.

A god shimmered into existence next to Hestia. He looked about twenty-five, with curly salt-and-pepper hair and elfish features. He wore a military pilot's flight suit, with tiny bird's wings fluttering on his helmet and his black leather boots. In the crook of his arm was a long staff entwined with two living serpents.