“I know,” she murmured. “Gods of Olympus, Percy, I know.”

Annabeth was almost glad for the job of keeping the Doors closed. The terror racing through her heart at least kept her from dissolving into misery. Abandoning Damasen and Bob had been the hardest thing she’d ever done.

For years at Camp Half-Blood, she had chafed as other campers went on quests while she stayed behind. She’d watched as others gained glory…or failed and didn’t come back. Since she was seven years old, she had thought: Why don’t I get to prove my skills? Why can’t I lead a quest?

Now she realized that the hardest test for a child of Athena wasn’t leading a quest or facing death in combat. It was making the strategic decision to step back, to let someone else take the brunt of the danger—especially when that person was your friend. She had to face the fact that she couldn’t protect everyone she loved. She couldn’t solve every problem.

She hated it, but she didn’t have time for self-pity. She blinked away her tears.

“Percy, the Doors,” she warned.

The panels had started to slide apart, letting in a whiff of…ozone? Sulfur?

Percy pushed on his side furiously and the crack closed. His eyes blazed with anger. She hoped he wasn’t mad at her, but if he was, she couldn’t blame him.

If it keeps him going, she thought, then let him be angry.

“I will kill Gaea,” he muttered. “I will tear her apart with my bare hands.”

Annabeth nodded, but she was thinking about Tartarus’s boast. He could not be killed. Neither could Gaea. Against such power, even Titans and giants were hopelessly outmatched. Demigods stood no chance.

She also remembered Bob’s warning: This may not be the last sacrifice you must make to stop Gaea.

She felt that truth deep in her bones.

“Twelve minutes,” she murmured. “Just twelve minutes.”

She prayed to Athena that Bob could hold the UP button that long. She prayed for strength and wisdom. She wondered what they would find once they reached the top of this elevator ride.

If their friends weren’t there, controlling the other side…

“We can do this,” Percy said. “We have to.”

“Yeah,” Annabeth said. “Yeah, we do.”

They held the Doors shut as the elevator shuddered and the music played, while somewhere below them, a Titan and a giant sacrificed their lives for their escape.

HAZEL WASN’T PROUD OF CRYING.

After the tunnel collapsed, she wept and screamed like a two-year-old throwing a tantrum. She couldn’t move the debris that separated her and Leo from the others. If the earth shifted any more, the entire complex might collapse on their heads. Still, she pounded her fists against the stones and yelled curses that would’ve earned her a mouth-washing with lye soap back at St. Agnes Academy.

Leo stared at her, wide-eyed and speechless.

She wasn’t being fair to him.

The last time the two of them had been together, she’d zapped him into her past and shown him Sammy, his great-grandfather—Hazel’s first boyfriend. She’d burdened him with emotional baggage he didn’t need, and left him so dazed they had almost gotten killed by a giant shrimp monster.

Now here they were, alone again, while their friends might be dying at the hands of a monster army, and she was throwing a fit.

“Sorry.” She wiped her face.

“Hey, you know…” Leo shrugged. “I’ve attacked a few rocks in my day.”

She swallowed with difficulty. “Frank is…he’s—”

“Listen,” Leo said. “Frank Zhang has moves. He’s probably gonna turn into a kangaroo and do some marsupial jujitsu on their ugly faces.”

He helped her to her feet. Despite the panic simmering inside her, she knew Leo was right. Frank and the others weren’t helpless. They would find a way to survive. The best thing she and Leo could do was carry on.

She studied Leo. His hair had grown out longer and shaggier, and his face was leaner, so he looked less like an imp and more like one of those willowy elves in the fairy tales. The biggest difference was his eyes. They constantly drifted, as if Leo was trying to spot something over the horizon.

“Leo, I’m sorry,” she said.

He raised an eyebrow. “Okay. For what?”

“For…” She gestured around her helplessly. “Everything. For thinking you were Sammy, for leading you on. I mean, I didn’t mean to, but if I did—”

“Hey.” He squeezed her hand, though Hazel sensed nothing romantic in the gesture. “Machines are designed to work.”

“Uh, what?”

“I figure the universe is basically like a machine. I don’t know who made it, if it was the Fates, or the gods, or capital-G God, or whatever. But it chugs along the way it’s supposed to most of the time. Sure, little pieces break and stuff goes haywire once in a while, but mostly…things happen for a reason. Like you and me meeting.”

“Leo Valdez,” Hazel marveled, “you’re a philosopher.”

“Nah,” he said. “I’m just a mechanic. But I figure my bisabuelo Sammy knew what was what. He let you go, Hazel. My job is to tell you that it’s okay. You and Frank—you’re good together. We’re all going to get through this. I hope you guys get a chance to be happy. Besides, Zhang couldn’t tie his shoes without your help.”

“That’s mean,” Hazel chided, but she felt like something was untangling inside her—a knot of tension she’d been carrying for weeks.

Leo really had changed. Hazel was starting to think she’d found a good friend.

“What happened to you when you were on your own?” she asked. “Who did you meet?”

Leo’s eye twitched. “Long story. I’ll tell you sometime, but I’m still waiting to see how it shakes out.”

“The universe is a machine,” Hazel said, “so it’ll be fine.”

“Hopefully.”

“As long as it’s not one of your machines,” Hazel added. “Because your machines never do what they’re supposed to.”

“Yeah, ha-ha.” Leo summoned fire into his hand. “Now, which way, Miss Underground?”

Hazel scanned the path in front of them. About thirty feet down, the tunnel split into four smaller arteries, each one identical, but the one on the left radiated cold.

“That way,” she decided. “It feels the most dangerous.”

“I’m sold,” said Leo.

They began their descent.

As soon as they reached the first archway, the polecat Gale found them.

She scurried up Hazel’s side and curled around her neck, chittering crossly as if to say: Where have you been? You’re late.

“Not the farting weasel again,” Leo complained. “If that thing lets loose in close quarters like this, with my fire and all, we’re gonna explode.”

Gale barked a polecat insult at Leo.

Hazel hushed them both. She could sense the tunnel ahead, sloping gently down for about three hundred feet, then opening into a large chamber. In that chamber was a presence…cold, heavy, and powerful. Hazel hadn’t felt anything like it since the cave in Alaska where Gaea had forced her to resurrect Porphyrion the giant king. Hazel had thwarted Gaea’s plans that time, but she’d had to pull down the cavern, sacrificing her life and her mother’s. She wasn’t anxious to have a similar experience.

“Leo, be ready,” she whispered. “We’re getting close.”

“Close to what?”

A woman’s voice echoed down the corridor: “Close to me.”

A wave of nausea hit Hazel so hard her knees buckled. The whole world shifted. Her sense of direction, usually flawless underground, became completely unmoored.

She and Leo didn’t seem to move, but suddenly they were three hundred feet down the corridor, at the entrance of the chamber.

“Welcome,” said the woman’s voice. “I’ve looked forward to this.”

Hazel’s eyes swept the cavern. She couldn’t see the speaker.

The room reminded her of the Pantheon in Rome, except this place had been decorated in Hades Modern.

The obsidian walls were carved with scenes of death: plague victims, corpses on the battlefield, torture chambers with skeletons hanging in iron cages—all of it embellished with precious gems that somehow made the scenes even more ghastly.

As in the Pantheon, the domed roof was a waffle pattern of recessed square panels, but here each panel was a stela—a grave marker with Ancient Greek inscriptions. Hazel wondered if actual bodies were buried behind them. With her underground senses out of whack, she couldn’t be sure.

She saw no other exits. At the apex of the ceiling, where the Pantheon’s skylight would’ve been, a circle of pure black stone gleamed, as if to reinforce the sense that there was no way out of this place—no sky above, only darkness.

Hazel’s eyes drifted to the center of the room.

“Yep,” Leo muttered. “Those are doors, all right.”

Fifty feet away was a set of freestanding elevator doors, their panels etched in silver and iron. Rows of chains ran down either side, bolting the frame to large hooks in the floor.

The area around the doors was littered with black rubble. With a tightening sense of anger, Hazel realized that an ancient altar to Hades had once stood there. It had been destroyed to make room for the Doors of Death.

“Where are you?” she shouted.

“Don’t you see us?” taunted the woman’s voice. “I thought Hecate chose you for your skill.”

Another bout of queasiness churned through Hazel’s gut. On her shoulder, Gale barked and passed gas, which didn’t help.

Dark spots floated in Hazel’s eyes. She tried to blink them away, but they only turned darker. The spots consolidated into a twenty-foot-tall shadowy figure looming next to the Doors.

The giant Clytius was shrouded in the black smoke, just as she’d seen in her vision at the crossroads, but now Hazel could dimly make out his form—dragon-like legs with ash-colored scales; a massive humanoid upper body encased in Stygian armor; long, braided hair that seemed to be made from smoke. His complexion was as dark as Death’s (Hazel should know, since she had met Death personally). His eyes glinted cold as diamonds. He carried no weapon, but that didn’t make him any less terrifying.

Leo whistled. “You know, Clytius…for such a big dude, you’ve got a beautiful voice.”

“Idiot,” hissed the woman.

Halfway between Hazel and the giant, the air shimmered. The sorceress appeared.

She wore an elegant sleeveless dress of woven gold, her dark hair piled into a cone, encircled with diamonds and emeralds. Around her neck hung a pendant like a miniature maze, on a cord set with rubies that made Hazel think of crystallized blood drops.

The woman was beautiful in a timeless, regal way—like a statue you might admire but could never love. Her eyes sparkled with malice.

“Pasiphaë,” Hazel said.

The woman inclined her head. “My dear Hazel Levesque.”