“Stupid rock gods!” Leo yelled from the helm. “That’s the third time I’ve had to replace that mast! You think they grow on trees?”

Nico frowned. “Masts are from trees.”

“That’s not the point!” Leo snatched up one of his controls, a jury-rigged Nintendo Wii stick, and spun it in a circle. A few feet away, a trapdoor opened in the deck. A Celestial bronze cannon rose. Hazel just had time to cover her ears before it discharged into the sky, spraying a dozen metal spheres that trailed green fire. The spheres grew spikes in midair, like helicopter blades, and spun away into the fog.

A moment later, a series of explosions crackled across the mountains, followed by the outraged roar of mountain gods.

“Ha!” Leo yelled.

Unfortunately, Hazel guessed, judging from their last two encounters, Leo’s newest weapon had only annoyed the numina.

Another boulder whistled through the air off to their starboard side.

Nico yelled, “Get us out of here!”

Leo muttered some unflattering comments about numina, but he turned the wheel. The engines hummed. Magical rigging lashed itself tight, and the ship tacked to port. The Argo II picked up speed, retreating northwest, as they’d been doing for the past two days.

Hazel didn’t relax until they were out of the mountains. The fog cleared. Below them, morning sunlight illuminated the Italian countryside—rolling green hills and golden fields not too different from those in Northern California. Hazel could almost imagine she was sailing home to Camp Jupiter.

The thought weighed on her chest. Camp Jupiter had only been her home for nine months, since Nico had brought her back from the Underworld. But she missed it more than her birthplace of New Orleans, and definitely more than Alaska, where she’d died back in 1942.

She missed her bunk in the Fifth Cohort barracks. She missed dinners in the mess hall, with wind spirits whisking platters through the air and legionnaires joking about the war games. She wanted to wander the streets of New Rome, holding hands with Frank Zhang. She wanted to experience just being a regular girl for once, with an actual sweet, caring boyfriend.

Most of all, she wanted to feel safe. She was tired of being scared and worried all the time.

She stood on the quarterdeck as Nico picked mast splinters out of his arms and Leo punched buttons on the ship’s console.

“Well, that was sucktastic,” Leo said. “Should I wake the others?”

Hazel was tempted to say yes, but the other crewmembers had taken the night shift and had earned their rest. They were exhausted from defending the ship. Every few hours, it seemed, some Roman monster had decided the Argo II looked like a tasty treat.

A few weeks ago, Hazel wouldn’t have believed that anyone could sleep through a numina attack, but now she imagined her friends were still snoring away belowdecks. Whenever she got a chance to crash, she slept like a coma patient.

“They need rest,” she said. “We’ll have to figure out another way on our own.”

“Huh.” Leo scowled at his monitor. In his tattered work shirt and grease-splattered jeans, he looked like he’d just lost a wrestling match with a locomotive.

Ever since their friends Percy and Annabeth had fallen into Tartarus, Leo had been working almost nonstop. He’d been acting angrier and even more driven than usual.

Hazel worried about him. But part of her was relieved by the change. Whenever Leo smiled and joked, he looked too much like Sammy, his great-grandfather…Hazel’s first boyfriend back in 1942.

Ugh, why did her life have to be so complicated?

“Another way,” Leo muttered. “Do you see one?”

On his monitor glowed a map of Italy. The Apennine Mountains ran down the middle of the boot-shaped country. A green dot for the Argo II blinked on the western side of the range, a few hundred miles north of Rome. Their path should have been simple. They needed to get to a place called Epirus in Greece and find an old temple called the House of Hades (or Pluto, as the Romans called him; or as Hazel liked to think of him: the World’s Worst Absent Father).

To reach Epirus, all they had to do was go straight east—over the Apennines and across the Adriatic Sea. But it hadn’t worked out that way. Each time they tried to cross the spine of Italy, the mountain gods attacked.

For the past two days they’d skirted north, hoping to find a safe pass, with no luck. The numina montanum were sons of Gaea, Hazel’s least favorite goddess. That made them very determined enemies. The Argo II couldn’t fly high enough to avoid their attacks; and even with all its defenses, the ship couldn’t make it across the range without being smashed to pieces.

“It’s our fault,” Hazel said. “Nico’s and mine. The numina can sense us.”

She glanced at her half brother. Since they’d rescued him from the giants, he’d started to regain his strength, but he was still painfully thin. His black shirt and jeans hung off his skeletal frame. Long, dark hair framed his sunken eyes. His olive complexion had turned a sickly greenish-white, like the color of tree sap.

In human years, he was barely fourteen, just a year older than Hazel; but that didn’t tell the whole story. Like Hazel, Nico di Angelo was a demigod from another era. He radiated a kind of old energy—a melancholy that came from knowing he didn’t belong in the modern world.

Hazel hadn’t known him very long, but she understood, even shared his sadness. The children of Hades (Pluto—whichever) rarely had happy lives. And judging from what Nico had told her the night before, their biggest challenge was yet to come when they reached the House of Hades—a challenge he’d implored her to keep secret from the others.

Nico gripped the hilt of his Stygian iron sword. “Earth spirits don’t like children of the Underworld. That’s true. We get under their skin—literally. But I think the numina could sense this ship anyway. We’re carrying the Athena Parthenos. That thing is like a magical beacon.”

Hazel shivered, thinking of the massive statue that took up most of the hold. They’d sacrificed so much, saving it from the cavern under Rome; but they had no idea what to do with it. So far the only thing it seemed to be good for was alerting more monsters to their presence.

Leo traced his finger down the map of Italy. “So crossing the mountains is out. Thing is, they go a long way in either direction.”

“We could go by sea,” Hazel suggested. “Sail around the southern tip of Italy.”

“That’s a long way,” Nico said. “Plus, we don’t have…” His voice cracked. “You know…our sea expert, Percy.”

The name hung in the air like an impending storm.

Percy Jackson, son of Poseidon…probably the demigod Hazel admired most. He’d saved her life so many times on their quest to Alaska; but when he had needed Hazel’s help in Rome, she’d failed him. She’d watched, powerless, as he and Annabeth had plunged into that pit.…

Hazel took a deep breath. Percy and Annabeth were still alive. She knew that in her heart. She could still help them if she could get to the House of Hades, if she could survive the challenge Nico had warned her about.…

“What about continuing north?” she asked. “There has to be a break in the mountains, or something.”

Leo fiddled with the bronze Archimedes sphere that he’d installed on the console—his newest and most dangerous toy. Every time Hazel looked at the thing, her mouth went dry. She worried that Leo would turn the wrong combination on the sphere and accidentally eject them all from the deck, or blow up the ship, or turn the Argo II into a giant toaster.

Fortunately, they got lucky. The sphere grew a camera lens and projected a 3D image of the Apennine Mountains above the console.

“I dunno.” Leo examined the holograph. “I don’t see any good passes to the north. But I like that idea better than backtracking south. I’m done with Rome.”

No one argued with that. Rome had not been a good experience.

“Whatever we do,” Nico said, “we have to hurry. Every day that Annabeth and Percy are in Tartarus…”

He didn’t need to finish. They had to hope Percy and Annabeth could survive long enough to find the Tartarus side of the Doors of Death. Then, assuming the Argo II could reach the House of Hades, they might be able to open the doors on the mortal side, save their friends, and seal the entrance, stopping Gaea’s forces from being reincarnated in the mortal world, over and over.

Yes…nothing could go wrong with that plan.

Nico scowled at the Italian countryside below them. “Maybe we should wake the others. This decision affects us all.”

“No,” Hazel said. “We can find a solution.”

She wasn’t sure why she felt so strongly about it, but since leaving Rome, the crew had started to lose its cohesion. They’d been learning to work as a team. Then bam…their two most important members fell into Tartarus. Percy had been their backbone. He’d given them confidence as they sailed across the Atlantic and into the Mediterranean. As for Annabeth—she’d been the de facto leader of the quest. She’d recovered the Athena Parthenos single-handedly. She was the smartest of the seven, the one with the answers.

If Hazel woke up the rest of the crew every time they had a problem, they’d just start arguing again, feeling more and more hopeless.

She had to make Percy and Annabeth proud of her. She had to take the initiative. She couldn’t believe her only role in this quest would be what Nico had warned her of—removing the obstacle waiting for them in the House of Hades. She pushed the thought aside.

“We need some creative thinking,” she said. “Another way to cross those mountains, or a way to hide ourselves from the numina.”

Nico sighed. “If I was on my own, I could shadow-travel. But that won’t work for an entire ship. And honestly, I’m not sure I have the strength to even transport myself anymore.”

“I could maybe rig some kind of camouflage,” Leo said, “like a smoke screen to hide us in the clouds.” He didn’t sound very enthusiastic.

Hazel stared down at the rolling farmland, thinking about what lay beneath it—the realm of her father, lord of the Underworld. She’d only met Pluto once, and she hadn’t even realized who he was. She certainly had never expected help from him—not when she was alive the first time, not during her time as a spirit in the Underworld, not since Nico had brought her back to the world of the living.

Her dad’s servant Thanatos, god of death, had suggested that Pluto might be doing Hazel a favor by ignoring her. After all, she wasn’t supposed to be alive. If Pluto took notice of her, he might have to return her to the land of the dead.

Which meant calling on Pluto would be a very bad idea. And yet…

Please, Dad, she found herself praying. I have to find a way to your temple in Greece—the House of Hades. If you’re down there, show me what to do.

At the edge of the horizon, a flicker of movement caught her eye—something small and beige racing across the fields at incredible speed, leaving a vapor trail like a plane’s.