IN THE PAST nine months, Mia has never felt more free.

Then again, the only time she thinks she's ever felt free was when she was adventuring around the continent with Percy, Annabeth, Grover, and Tyson.

No. She can't think about that. Not now. Not when she's been having the time of her life, traveling between the Underworld and Camp Jupiter and countries that she's never been to.

"Where are we going next?" Mia asked her stepbrother, her new partner in crime, her new ride or die, even, as they waited for her stepsister and his half-sister, Hazel.

"I think we can't go anywhere," Nico told her. "The Feast of Fortuna is soon, remember?"

"Really?" Mia took out her phone, which she really only had because she's technically the CEO of the Starfury company, and looked at the date. "Huh. It is soon. Does that mean—"

"Hey," Hazel's voice called out to them. "I've brought a friend."

Mia turned, and her breath stopped.

There was no way it was him. Yet, it had to have been him, with his unruly black hair, striking green eyes, and the stained and torn orange Camp Half-Blood shirt and the camp necklace around his neck.

Mia looked at Nico and widened her eyes once at him in panic. He sent her a glare, telling her to act normal. She'd gotten good at discerning his expressions over the months.

"This is Percy Jackson," Hazel said. "He's a good guy. Percy, this is my brother, the son of Pluto, and my sister, the daughter of Proserpina."

Nico held out his hand. "Pleased to meet you," he said. "I'm Nico di Angelo, and this is my associate, Amelia Starfury."

Percy scowled at both of them. "I — I know you. Both of you."

Mia raised her eyebrows subtly. "Do you?" She and Nico looked at Hazel for explanation. Gaslight, gatekeep, girlboss.

"Um . . . Percy's lost his memory." Hazel told them what had happened when Percy had arrived at the gates.

"So, Nico, Amelia," Hazel continued, her voice cautious, "I thought . . . you know, you both travel all over. Maybe you've met demigods like Percy before, or . . ."

Nico's expression turned as dark as the night sky. Mia knew that expression: drop it.

"This story about Gaea's army," Nico said. "You warned Reyna?"

Percy nodded. "Who is Gaea, anyway?"

"She's the earth goddess," Mia said, looking down at the ground so she could ignore Percy's gaze on her. "The oldest goddess of all. She's in a deep sleep most of the time, but she hates the gods and their children."

"Mother Earth . . . is evil?" Percy asked.

"Very," Mia said, trying to make herself sound bored. "She convinced her son, the Titan Kronos — sorry, Saturn — to kill his dad, Uranus, and take over the world. The Titans ruled for a long time. Then the Titans' children, the Olympian gods, overthrew them."

"That story seems familiar," Percy sounded surprised, like he was remembering the Titan War, and Mia tried not to look at him. "But I don't think I ever heard the part about Gaea."

Nico shrugged. "She got mad when the gods took over. She took a new husband — Tartarus, the spirit of the abyss — and gave birth to a race of giants. They tried to destroy Mount Olympus, but the gods finally beat them. At least . . . the first time."

"The first time?" Percy repeated.

Nico glanced at Hazel, and then at Mia, who nodded.

"Last summer," Nico continued, "Saturn tried to make a comeback. There was a second Titan war. The Romans at Camp Jupiter stormed his headquarters on Mount Othrys, across the bay, and destroyed his throne. Saturn disappeared—" He hesitated, watching Percy's face.

"Anyway," Mia continued, Nico sending her a grateful look, "Saturn probably faded back to the abyss. We all thought the war was over. Now it looks like the Titans' defeat stirred up Gaea. She's starting to wake. We've heard reports of giants being reborn. If they mean to challenge the gods again, they'll probably start by destroying the demigods . . ."

"You've told Reyna this?" Percy asked.

"Of course," Nico said. "The Romans don't trust me, and they barely trust Amelia. That's why I was hoping she'd listen to you. Children of the Underworld . . . well, no offense, but they think that we're worse than children of Neptune. We're bad luck."

"They let Hazel stay here," Percy noted.

"That's different," Mia said.

"Why?"

"Percy," Hazel cut in, "look, the giants aren't the worst problem. Even . . . even Gaea isn't the worst problem. The thing you noticed about the gorgons, how they wouldn't die, that's our biggest worry." She looked at Mia and Nico.

"Nico, Amelia, and I," Hazel said carefully, "we think that what's happening is . . . Death isn't—"

Before she could finish, a shout came from down the hill.

Frank Zhang, Hazel's friend, jogged toward them, wearing jeans, a purple camp shirt, and a denim jacket. His hands were covered with grease from cleaning weapons.

He reached the shrine. "Hey, Nico, Amelia . . ."

"Frank." Nico smiled. He found Frank amusing because he was the only one at camp who wasn't uneasy around the children of the Underworld. Mia just thought that he was plainly adorable.

"Reyna sent me to get Percy," he said. "Did Octavian accept you?"

"Yeah," Percy said. "He slaughtered my panda."

"He . . . oh. The augury? Yeah, teddy bears must have nightmares about that guy. But you're in! We need to get you cleaned up before evening muster."

"You're right," Hazel said. "We'd better—"

"Frank," Nico interrupted, "why don't you take Percy down? Hazel, Amelia and I will be along soon."

"That's — that's a good idea," Hazel said weakly. "Go ahead, guys. We'll catch up."

Percy looked at Mia and Nico one more time. "I'd like to talk with you two some more. I can't shake the feeling—"

"Sure," Nico agreed. "Later. We'll be staying overnight."

"We will?" Mia asked, looking at her brother with her eyebrows raised the tiniest bit.

"Go on, Percy," Nico said. "Settle in." He turned to Hazel. "My sisters and I need to talk."

"You both know him, don't you," Hazel said.

They sat on the roof of Pluto's shrine, which was covered with bones and diamonds. As far as Mia knew, the bones had always been there. The diamonds were because of Hazel's powers. If she sat anywhere too long, or just got anxious, they started popping up all around her like mushrooms after a rain. Several million dollars' worth of stones glittered on the roof, but fortunately the other campers wouldn't touch them. They knew better than to steal from temples — especially Pluto's — and the fauns never came up here.

Nico swung his feet as if he was ten years old, at that military school that had changed Mia's life forever. His Stygian iron sword lay by his side, next to Hazel's spatha. He gazed across the valley, where construction crews were working in the Field of Mars, building fortifications for tonight's games.

"Percy Jackson," He said his name like Mia did all those years: in awe, in love. "Hazel, we have to be careful what we say. Important things are at work here. Some secrets need to stay secret. You of all people — you should understand that."

Mia saw Hazel's cheeks turn red. "But he's not like . . . like me?"

"No," Nico said. "I'm sorry I can't tell you more. I can't interfere, and neither can Amelia. Percy has to find his own way at this camp."

"Is he dangerous?" Hazel asked.

Nico managed a dry smile. "Very. To his enemies. But he's not a threat to Camp Jupiter. You can trust him."

"Like I trust you," Hazel said bitterly.

Nico looked at Mia with a bail me out of this expression. Around him, bones began to quiver as if they were trying to form a new skeleton. Whenever he got moody, Nico had that effect on the dead, kind of like Hazel's curse.

"Hey, Hazel, I know this is hard," Mia said. "But you have a second chance. You can make things right."

"Nothing about this is right," Hazel said. "If they find out the truth about me—"

"They won't," Mia promised. "They'll call a quest soon. They have to. You'll make us proud. Trust us. Trust me, please."

Hazel stared at her. "Are you sure?"

"Hey, you can't be any more of a disappointment than I am," Mia shrugged. "But I'm confident in you. You have a lot of potential, Hazel. To be great. To be . . ."

To be everything that Mia couldn't be. She noticed that Nico tried to meet her gaze, but she refused to.

"Then it's true about Death?" Hazel diverted the conversation. "Is Alcyoneus to blame?"

"I think so," Nico said. "It's getting bad in the Underworld. Dad's going crazy trying to keep things under control. From what Percy said about the gorgons, things are getting worse up here, too. But look, that's why you're here. All that stuff in your past — you can make something good come out of it. You belong at Camp Jupiter."

"Wow, di Angelo," Mia mused, "who knew you could be so uplifting?"

"Shut up, Starfury," he warned her, but she's been with him long enough to know that he wouldn't do anything dire to her. "You know how bad things are."

"Yeah . . ." she sighed. "Mother's worried. She's on Olympus, of course, but . . . she knows how bad things are."

"Has she given you any word?"

"Just to keep up the pretenses, now more than ever," Mia let out a bitter laugh, looking out at the horizon, at the setting sun. "As if I need the reminder. The lies have been stacking up since I was born. I'm so good at it, I could speak for a whole week with nothing but lies."

Nico snorted. "I couldn't stand you if all you told me were lies."

"What a shame," she told him. "Because you're stuck with me as long as you live, and even after that. That's what you get after making that deal with me."

He hummed in agreement, and they sat in comfortable silence.

At least, until she heard his slightly panicked voice. "Hazel? Hazel . . ."

Mia looked to her side and saw her stepsister lying down, eyes glassy and staring up at the sky unblinkingly. She shook Hazel's shoulders until she came back to herself. "You did it again."

"S-sorry," Hazel murmured.

"Don't be," Mia said. "Where were you?"

"My mother's apartment. The day we moved."

Nico nodded. "You have to work on controlling those memories," he warned, his softness fading away just as quickly as it came. "If a flashback like that happens when you're in combat—"

"I know," Hazel said. "I'm trying."

Mia squeezed her hand. "It's okay. I think it's a side effect from . . . you know, your time in the Underworld. Hopefully it'll get easier."

"I can't go north again," Hazel said. "Nico, Amelia, if I have to go back to where it happened—"

"You'll be fine," Nico promised. "You'll have friends this time. Amelia will probably come with you. And Percy Jackson — he's got a role to play in this. You can sense that, can't you? He's a good person to have at your side."

Mia bit her lip, looking at Nico uncertainly. Her mother and his father had told them that she was directly a part of this prophecy — she knew that for certain, because she never could catch a break. But having Percy here, right now, when her betrayal still hurt as badly as the day she'd been found out — it was bad. She had a bad feeling about all of this.

He just looked at her knowingly, exasperatedly. He'd seen this particular look from her before. He knew her just as well as she knew him, if not even more.

Endure. You have a million promises to fulfill once you're done here.

"Where did he come from?" Hazel asked, bringing Mia away from her thoughts. "Why do the ghosts call him the Greek?"

Before she or Nico could respond, horns blew across the river. The legionnaires were gathering for evening muster.

"We'd better get down there," Nico said. "I have a feeling tonight's war games are going to be interesting."