The monstrous army swarmed him, but the Maeonian drakon flattened everything in its path, sweeping its tail and spraying poison while Damasen jabbed at Tartarus, forcing the G.o.d to retreat like a cornered lion.

Bob stumbled away from the battle, his sabre-toothed cat at his side. Percy gave them as much cover as he could causing blood vessels in the ground to burst one after the other. Some monsters were vaporized in Styx water. Others got a Cocytus shower and collapsed, weeping hopelessly. Others were doused with liquid Lethe and stared blankly around them, no longer sure where they were or even who they were.

Bob limped to the Doors. Golden ichor flowed from the wounds on his arms and chest. His janitor's outfit hung in tatters. His posture was twisted and hunched, as if Tartarus breaking the spear had broken something inside him. Despite all that, he was grinning, his silver eyes bright with satisfaction.

'Go,' he ordered. 'I will hold the b.u.t.ton.'

Percy gawked at him. 'Bob, you're in no condition '

'Percy.' Annabeth's voice threatened to break. She hated herself for letting Bob do this, but she knew it was the only way. 'We have to.'

'We can't just leave them!'

'You must, friend.' Bob clapped Percy on the arm, nearly knocking him over. 'I can still press a b.u.t.ton. And I have a good cat to guard me.'

Small Bob the sabre-toothed growled in agreement.

'Besides,' Bob said, 'it is your destiny to return to the world. Put an end to this madness of Gaia.'

A screaming Cyclops, sizzling from poison spray, sailed over their heads.

Fifty yards away, the Maeonian drakon trampled through monsters, its feet making sickening squish squish noises as if stomping grapes. On its back, Damasen yelled insults and jabbed at the G.o.d of the pit, taunting Tartarus further away from the Doors.

Tartarus lumbered after him, his iron boots making craters in the ground.

You cannot kill me! he bellowed. I am the pit itself. You might as well try to kill the earth. Gaia and I we are eternal. We own you, flesh and spirit!

He brought down his ma.s.sive fist, but Damasen sidestepped, impaling his javelin in the side of Tartarus's neck.

Tartarus growled, apparently more annoyed than hurt. He turned his swirling vacuum face towards the giant, but Damasen got out of the way in time. A dozen monsters were sucked into the vortex and disintegrated.

'Bob, don't!' Percy said, his eyes pleading. 'He'll destroy you permanently. No coming back. No regeneration.'

Bob shrugged. 'Who knows what will be? You must go now. Tartarus is right about one thing. We cannot defeat him. We can only buy you time.'

The Doors tried to close on Annabeth's foot.

'Twelve minutes,' said the t.i.tan. 'I can give you that.'

'Percy ... hold the Doors.' Annabeth jumped and threw her arms around the t.i.tan's neck. She kissed his cheek, her eyes so full of tears she couldn't see straight. Bob's stubbly face smelled of cleaning supplies fresh lemony furniture polish and Murphy Oil wood soap.

'Monsters are eternal,' she told him, trying to keep herself from sobbing. 'We will remember you and Damasen as heroes, as the best t.i.tan and the best giant. We'll tell our children. We'll keep the story alive. Some day, you will regenerate.'

Bob ruffled her hair. Smile lines crinkled around his eyes. 'That is good. Until then, my friends, tell the sun and the stars h.e.l.lo for me. And be strong. This may not be the last sacrifice you must make to stop Gaia.'

He pushed her away gently. 'No more time. Go.'

Annabeth grabbed Percy's arm. She dragged him into the elevator car. She had one last glimpse of the Maeonian drakon shaking an ogre like a sock puppet, Damasen jabbing at Tartarus's legs.

The G.o.d of the pit pointed at the Doors of Death and yelled: Monsters, stop them!

Small Bob the sabre-toothed crouched and snarled, ready for action.

Bob winked at Annabeth. 'Hold the Doors closed on your side,' he said. 'They will resist your pa.s.sage. Hold them '

The panels slid shut.

LXXII.

ANNABETH.

'PERCY, HELP ME!' ANNABETH YELPED.

She shoved her entire body against the left door, pressing it towards the centre. Percy did the same on the right. There were no handles, or anything else to hold on to. As the elevator car ascended, the Doors shook and tried to open, threatening to spill them into whatever was between life and death.

Annabeth's shoulders ached. The elevator's easy-listening music didn't help. If all monsters had to hear that song about liking pina coladas and getting caught in the rain, no wonder they were in the mood for carnage when they reached the mortal world.

'We left Bob and Damasen,' Percy croaked. 'They'll die for us, and we just '

'I know,' she murmured. 'G.o.ds of Olympus, Percy, I know.'

Annabeth was almost glad of 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? Sulphur?

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 Gaia,' 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 Gaia. Against such power, even t.i.tans and giants were hopelessly outmatched. DemiG.o.ds stood no chance.

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

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 b.u.t.ton 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 t.i.tan and a giant sacrificed their lives for their escape.

LXXIII.

HAZEL.

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 been 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 s.h.a.ggier, 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 G.o.ds or capital-G G.o.d 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 marvelled, '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.