Phoebe grumbled, but soon Leo and Jason were also dressed in silvery winter clothes that were incredibly lightweight and warm. The hot chocolate was first-rate.

"Cheers!" said Coach Hedge. He crunched down his plastic thermos cup.

"That cannot be good for your intestines," Leo said.

Thalia patted Piper on the back. "You up for moving?"

Piper nodded. "Thanks to Phoebe, yeah. You guys are really good at this wilderness survival thing. I feel like I could run ten miles."

Thalia winked at Jason. "She's tough for a child of Aphrodite. I like this one."

"Hey, I could run ten miles too," Leo volunteered. "Tough Hephaestus kid here. Let's. .h.i.t it."

Naturally, Thalia ignored him.

It took Phoebe exactly six seconds to break camp, which Leo could not believe. The tent self-collapsed into a square the size of a pack of chewing gum. Leo wanted to ask her for the blueprints, but they didn't have time.

Thalia ran uphill through the snow, hugging a tiny little path on the side of the mountain, and soon Leo was regretting trying to look macho, because the Hunters left him in the dust.

Coach Hedge leaped around like a happy mountain goat, coaxing them on like he used to do on track days at school. "Come on, Valdez! Pick up the pace! Let's chant. I've got a girl in Kalamazoo-"

"Let's not," Thalia snapped.

So they ran in silence.

Leo fell in next to Jason at the back of the group. "How you doing, man?"

Jason's expression was enough of an answer: Not good.

"Thalia takes it so calmly," Jason said. "Like it's no big deal that I appeared. I didn't know what I was expecting, but ... she's not like me. She seems so much more together."

"Hey, she's not fighting amnesia," Leo said. "Plus, she's had more time to get used to this whole demiG.o.d thing. You fight monsters and talk to G.o.ds for a while, you probably get used to surprises."

"Maybe," Jason said. "I just wish I understood what happened when I was two, why my mom got rid of me. Thalia ran away because of me."

"Hey, whatever's happened, it wasn't your fault. And your sister is pretty cool. She's a lot like you."

Jason took that in silence. Leo wondered if he'd said the right things. He wanted to make Jason feel better, but this was way outside his comfort zone.

Leo wished he could reach inside his tool belt and pick just the right wrench to fix Jason's memory-maybe a little hammer-bonk the sticking spot and make everything run right. That would be a lot easier than trying to talk it through. Not good with organic life forms. Thanks for those inherited traits, Dad.

He was so lost in thought, he didn't realize the Hunters had stopped. He slammed into Thalia and nearly sent them both down the side of the mountain the hard way. Fortunately, the Hunter was light on her feet. She steadied them both, then pointed up.

"That," Leo choked, "is a really large rock."

They stood near the summit of Pikes Peak. Below them the world was blanketed in clouds. The air was so thin, Leo could hardly breathe. Night had set in, but a full moon shone and the stars were incredible. Stretching out to the north and south, peaks of other mountains rose from the clouds like islands-or teeth.

But the real show was above them. Hovering in the sky, about a quarter mile away, was a ma.s.sive free-floating island of glowing purple stone. It was hard to judge its size, but Leo figured it was at least as wide as a football stadium and just as tall. The sides were rugged cliffs, riddled with caves, and every once in a while a gust of wind burst out with a sound like a pipe organ blast. At the top of the rock, bra.s.s walls ringed some kind of a fortress.

The only thing connecting Pikes Peak to the floating island was a narrow bridge of ice that glistened in the moonlight.

Then Leo realized the bridge wasn't exactly ice, because it wasn't solid. As the winds changed direction, the bridge snaked around-blurring and thinning, in some places even breaking into a dotted line like the vapor trail of a plane.

"We're not seriously crossing that," Leo said.

Thalia shrugged. "I'm not a big fan of heights, I'll admit. But if you want to get to Aeolus's fortress, this is the only way."

"Is the fortress always hanging there?" Piper asked. "How can people not notice it sitting on top of Pikes Peak?"

"The Mist," Thalia said. "Still, mortals do notice it indirectly. Some days, Pikes Peak looks purple. People say it's a trick of the light, but actually it's the color of Aeolus's palace, reflecting off the mountain face."

"It's enormous," Jason said.

Thalia laughed. "You should see Olympus, little brother."

"You're serious? You've been there?"

Thalia grimaced as if it wasn't a good memory. "We should go across in two different groups. The bridge is fragile."

"That's rea.s.suring," Leo said. "Jason, can't you just fly us up there?"

Thalia laughed. Then she seemed to realize Leo's question wasn't a joke. "Wait ... Jason, you can fly?"

Jason gazed up at the floating fortress. "Well, sort of. More like I can control the winds. But the winds up here are so strong, I'm not sure I'd want to try. Thalia, you mean ... you can't fly?"

For a second, Thalia looked genuinely afraid. Then she got her expression under control. Leo realized she was a lot more scared of heights than she was letting on.

"Truthfully," she said, "I've never tried. Might be better if we stuck to the bridge."

Coach Hedge tapped the ice vapor trail with his hoof, then jumped onto the bridge. Amazingly, it held his weight. "Easy! I'll go first. Piper, come on, girl. I'll give you a hand."

"No, that's okay," Piper started to say, but the coach grabbed her hand and dragged her up the bridge.

When they were about halfway, the bridge still seemed to be holding them just fine.

Thalia turned to her Hunter friend. "Phoebe, I'll be back soon. Go find the others. Tell them I'm on my way."

"You sure?" Phoebe narrowed her eyes at Leo and Jason, like they might kidnap Thalia or something.

"It's fine," Thalia promised.

Phoebe nodded reluctantly, then raced down the mountain path, the white wolves at her heels.

"Jason, Leo, just be careful where you step," Thalia said. "It hardly ever breaks."

"It hasn't met me yet," Leo muttered, but he and Jason led the way up the bridge.

Halfway up, things went wrong, and of course it was Leo's fault. Piper and Hedge had already made it safely to the top and were waving at them, encouraging them to keep climbing, but Leo got distracted. He was thinking about bridges-how he would design something way more stable than this shifting ice vapor business if this were his palace. He was pondering braces and support columns. Then a sudden revelation stopped him in his tracks.

"Why do they have a bridge?" he asked.

Thalia frowned. "Leo, this isn't a good place to stop. What do you mean?"

"They're wind spirits," Leo said. "Can't they fly?"

"Yes, but sometimes they need a way to connect to the world below."

"So the bridge isn't always here?" Leo asked.

Thalia shook her head. "The wind spirits don't like to anchor to the earth, but sometimes it's necessary. Like now. They know you're coming."

Leo's mind was racing. He was so excited he could almost feel his body's temperature rising. He couldn't quite put his thoughts into words, but he knew he was on to something important.

"Leo?" Jason said. "What are you thinking?"

"Oh, G.o.ds," Thalia said. "Keep moving. Look at your feet."

Leo shuffled backward. With horror, he realized his body temperature really was rising, just as it had years ago at that picnic table under the pecan tree, when his anger had gotten away from him. Now, excitement was causing the reaction. His pants steamed in the cold air. His shoes were literally smoking, and the bridge didn't like it. The ice was thinning.

"Leo, stop it," Jason warned. "You're going to melt it."

"I'll try," Leo said. But his body was overheating on its own, running as fast as his thoughts. "Listen, Jason, what did Hera call you in that dream? She called you a bridge."

"Leo, seriously, cool down," Thalia said. "I don't what you're talking about, but the bridge is-"

"Just listen," Leo insisted. "If Jason is a bridge, what's he connecting? Maybe two different places that normally don't get along-like the air palace and the ground. You had to be somewhere before this, right? And Hera said you were an exchange."

"An exchange." Thalia's eyes widened. "Oh, G.o.ds."

Jason frowned. "What are you two talking about?"

Thalia murmured something like a prayer. "I understand now why Artemis sent me here. Jason-she told me to hunt for Lycaon and I would find a clue about Percy. You are the clue. Artemis wanted us to meet so I could hear your story."

"I don't understand," he protested. "I don't have a story. I don't remember anything."

"But Leo's right," Thalia said. "It's all connected. If we just knew where-"

Leo snapped his fingers. "Jason, what did you call that place in your dream? That ruined house. The Wolf House?"

Thalia nearly choked. "The Wolf House? Jason, why didn't you tell me that! That's where they're keeping Hera?"

"You know where it is?" Jason asked.

Then the bridge dissolved. Leo would've fallen to his death, but Jason grabbed his coat and pulled him to safety. The two of them scrambled up the bridge, and when they turned, Thalia was on the other side of a thirty-foot chasm. The bridge was continuing to melt.

"Go!" Thalia shouted, backing down the bridge as it crumbled. "Find out where the giant is keeping Piper's dad. Save him! I'll take the Hunters to the Wolf House and hold it until you can get there. We can do both!"

"But where is the Wolf House?" Jason shouted.

"You know where it is, little brother!" She was so far away now that they could barely hear her voice over the wind. Leo was pretty sure she said: "I'll see you there. I promise."

Then she turned and raced down the dissolving bridge.

Leo and Jason had no time to stand around. They climbed for their lives, the ice vapor thinning under their feet. Several times, Jason grabbed Leo and used the winds to keep them aloft, but it was more like bungee jumping than flying.

When they reached the floating island, Piper and Coach Hedge pulled them aboard just as the last of the vapor bridge vanished. They stood gasping for breath at the base of a stone stairway chiseled into the side of the cliff, leading up to the fortress.

Leo looked back down. The top of Pikes Peak floated below them in a sea of clouds, but there was no sign of Thalia. And Leo had just burned their only exit.

"What happened?" Piper demanded. "Leo, why are your clothes smoking?"

"I got a little heated," he gasped. "Sorry, Jason. Honest. I didn't-"

"It's all right," Jason said, but his expression was grim. "We've got less than twenty-four hours to rescue a G.o.ddess and Piper's dad. Let's go see the king of the winds."

JASON HAD FOUND HIS SISTER AND lost her in less than an hour. As they climbed the cliffs of the floating island, he kept looking back, but Thalia was gone.

Despite what she'd said about meeting him again, Jason wondered. She'd found a new family with the Hunters, and a new mother in Artemis. She seemed so confident and comfortable with her life, Jason wasn't sure if he'd ever be part of it. And she seemed so set on finding her friend Percy. Had she ever searched for Jason that way?

Not fair, he told himself. She thought you were dead.

He could barely tolerate what she'd said about their mom. It was almost like Thalia had handed him a baby-a really loud, ugly baby-and said, Here, this is yours. Carry it. He didn't want to carry it. He didn't want to look at it or claim it. He didn't want to know that he had an unstable mother who'd gotten rid of him to appease a G.o.ddess. No wonder Thalia had run away.

Then he remembered the Zeus cabin at Camp Half-Blood-that tiny little alcove Thalia had used as a bunk, out of sight from the glowering statue of the sky G.o.d. Their dad wasn't much of a bargain, either. Jason understood why Thalia had renounced that part of her life too, but he was still resentful. He couldn't be so lucky. He was left holding the bag -literally.

The golden backpack of winds was strapped over his shoulders. The closer they got to Aeolus's palace, the heavier the bag got. The winds struggled, rumbling and b.u.mping around.

The only one who seemed in a good mood was Coach Hedge. He kept bounding up the slippery staircase and trotting back down. "Come on, cupcakes! Only a few thousand more steps!"

As they climbed, Leo and Piper left Jason in his silence. Maybe they could sense his bad mood. Piper kept glancing back, worried, as if he were the one who'd almost died of hypothermia rather than she. Or maybe she was thinking about Thalia's idea. They'd told her what Thalia had said on the bridge-how they could save both her dad and Hera-but Jason didn't really understand how they were going to do that, and he wasn't sure if the possibility had made Piper more hopeful or just more anxious.

Leo kept swatting his own legs, checking for signs that his pants were on fire. He wasn't steaming anymore, but the incident on the ice bridge had really freaked Jason out. Leo hadn't seemed to realize that he had smoke coming out his ears and flames dancing through his hair. If Leo started spontaneously combusting every time he got excited, they were going to have a tough time taking him anywhere. Jason imagined trying to get food at a restaurant. I'll have a cheeseburger and-Ahhh! My friend's on fire! Get me a bucket!

Mostly, though, Jason worried about what Leo had said. Jason didn't want to be a bridge, or an exchange, or anything else. He just wanted to know where he'd come from. And Thalia had looked so unnerved when Leo mentioned the burned-out house in his dreams-the place the wolf Lupa had told him was his starting point. How did Thalia know that place, and why did she a.s.sume Jason could find it?

The answer seemed close. But the nearer Jason got to it, the less it cooperated, like the winds on his back.

Finally they arrived at the top of the island. Bronze walls marched all the way around the fortress grounds, though Jason couldn't imagine who would possibly attack this place. Twenty-foot-high gates opened for them, and a road of polished purple stone led up to the main citadel-a white-columned rotunda, Greek style, like one of the monuments in Washington, D.C.-except for the cl.u.s.ter of satellite dishes and radio towers on the roof.

"That's bizarre," Piper said.

"Guess you can't get cable on a floating island," Leo said. "Dang, check this guy's front yard."

The rotunda sat in the center of a quarter-mile circle. The grounds were amazing in a scary way. They were divided into four sections like big pizza slices, each one representing a season.

The section on their right was an icy waste, with bare trees and a frozen lake. Snowmen rolled across the landscape as the wind blew, so Jason wasn't sure if they were decorations or alive.

To their left was an autumn park with gold and red trees. Mounds of leaves blew into patterns-G.o.ds, people, animals that ran after each other before scattering back into leaves.