Leo fiddled with his copper wires. He felt like an intruder. He shouldn’t be listening to this, but it also made him feel like he was getting to know Jason for the first time—like maybe being here now made up for those four months at Wilderness School, when Leo had just imagined they’d had a friendship.

“How did you guys get separated?” he asked.

Thalia squeezed her brother’s hand. “If I’d known you were alive … gods, things would’ve been so different. But when you were two, Mom packed us in the car for a family vacation. We drove up north, toward the wine country, to this park she wanted to show us. I remember thinking it was strange because Mom never took us anywhere, and she was acting super nervous. I was holding your hand, walking you toward this big building in the middle of the park, and …” She took a shaky breath. “Mom told me to go back to the car and get the picnic basket. I didn’t want to leave you alone with her, but it was only for a few minutes. When I came back … Mom was kneeling on the stone steps, hugging herself and crying. She said—she said you were gone. She said Hera claimed you and you were as good as dead. I didn’t know what she’d done. I was afraid she’d completely lost her mind. I ran all over the place looking for you, but you’d just vanished. She had to drag me away, kicking and screaming. For the next few days I was hysterical. I don’t remember everything, but I called the police on Mom and they questioned her for a long time. Afterward, we fought. She told me I’d betrayed her, that I should support her, like she was the only one who mattered. Finally I couldn’t stand it. Your disappearance was the last straw. I ran away from home, and I never went back, not even when Mom died a few years ago. I thought you were gone forever. I never told anyone about you—not even Annabeth or Luke, my two best friends. It was just too painful.”

“Chiron knew.” Jason’s voice sounded far away. “When I got to camp, he took one look at me and said, ‘You should be dead.’”

“That doesn’t make sense,” Thalia insisted. “I never told him.”

“Hey,” Leo said. “Important thing is you’ve got each other now, right? You two are lucky.”

Thalia nodded. “Leo’s right. Look at you. You’re my age. You’ve grown up.”

“But where have I been?” Jason said. “How could I be missing all that time? And the Roman stuff …”

Thalia frowned. “The Roman stuff?”

“Your brother speaks Latin,” Leo said. “He calls gods by their Roman names, and he’s got tattoos.” Leo pointed out the marks on Jason’s arm. Then he gave Thalia the rundown about the other weird stuff that had happened: Boreas turning into Aquilon, Lycaon calling Jason a “child of Rome,” and the wolves backing off when Jason spoke Latin to them.

Thalia plucked her bowstring. “Latin. Zeus sometimes spoke Latin, the second time he stayed with Mom. Like I said, he seemed different, more formal.”

“You think he was in his Roman aspect?” Jason asked. “And that’s why I think of myself as a child of Jupiter?”

“Possibly,” Thalia said. “I’ve never heard of something like that happening, but it might explain why you think in Roman terms, why you can speak Latin rather than Ancient Greek. That would make you unique. Still, it doesn’t explain how you’ve survived without Camp Half-Blood. A child of Zeus, or Jupiter, or whatever you want to call him—you would’ve been hounded by monsters. If you were on your own, you should’ve died years ago. I know I wouldn’t have been able to survive without friends. You would’ve needed training, a safe haven—”

“He wasn’t alone,” Leo blurted out. “We’ve heard about others like him.”

Thalia looked at him strangely. “What do you mean?”

Leo told her about the slashed-up purple shirt in Medea’s department store, and the story the Cyclopes told about the child of Mercury who spoke Latin.

“Isn’t there anywhere else for demigods?” Leo asked. “I mean besides Camp Half-Blood? Maybe some crazy Latin teacher has been abducting children of the gods or something, making them think like Romans.”

As soon as he said it, Leo realized how stupid the idea sounded. Thalia’s dazzling blue eyes studied him intently, making him feel like a suspect in a lineup.

“I’ve been all over the country,” Thalia mused. “I’ve never seen evidence of a crazy Latin teacher, or demigods in purple shirts. Still …” Her voice trailed off, like she’d just had a troubling thought.

“What?” Jason asked.

Thalia shook her head. “I’ll have to talk to the goddess. Maybe Artemis will guide us.”

“She’s still talking to you?” Jason asked. “Most of the gods have gone silent.”

“Artemis follows her own rules,” Thalia said. “She has to be careful not to let Zeus know, but she thinks Zeus is being ridiculous closing Olympus. She’s the one who set us on the trail of Lycaon. She said we’d find a lead to a missing friend of ours.”

“Percy Jackson,” Leo guessed. “The guy Annabeth is looking for.”

Thalia nodded, her face full of concern.

Leo wondered if anyone had ever looked that worried all the times he’d disappeared. He kind of doubted it.

“So what would Lycaon have to do with it?” Leo asked. “And how does it connect to us?”

“We need to find out soon,” Thalia admitted. “If your deadline is tomorrow, we’re wasting time. Aeolus could tell you—”

The white wolf appeared again at the doorway and yipped insistently.

“I have to get moving.” Thalia stood. “Otherwise I’ll lose the other Hunters’ trail. First, though, I’ll take you to Aeolus’s palace.”

“If you can’t, it’s okay,” Jason said, though he sounded kind of distressed.

“Oh, please.” Thalia smiled and helped him up. “I haven’t had a brother in years. I think I can stand a few minutes with you before you get annoying. Now, let’s go!”

WHEN LEO SAW HOW WELL PIPER AND HEDGE were being treated, he was thoroughly offended.

He’d imagined them freezing their hindquarters off in the snow, but the Hunter Phoebe had set up this silver tent pavilion thing right outside the cave. How she’d done it so fast, Leo had no idea, but inside was a kerosene heater keeping them toasty warm and a bunch of comfy throw pillows. Piper looked back to normal, decked out in a new parka, gloves, and camo pants like a Hunter. She and Hedge and Phoebe were kicking back, drinking hot chocolate.

“Oh, no way,” Leo said. “We’ve been sitting in a cave and you get the luxury tent? Somebody give me hypothermia. I want hot chocolate and a parka!”

Phoebe sniffed. “Boys,” she said, like it was the worst insult she could think of.

“It’s all right, Phoebe,” Thalia said. “They’ll need extra coats. And I think we can spare some chocolate.”

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 hit 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 demigod thing. You fight monsters and talk to gods 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 massive 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, brass 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.