'Thanks ...' She gently disentangled herself from his arms. 'Can you tell what's in front us?'

'Water,' he said. 'I'm still not looking. I don't think it's safe yet.'

'Agreed.'

'I can sense a river ... or maybe it's a moat. It's blocking our path, flowing left to right through a channel cut in the rock. The opposite side is about twenty feet away.'

Annabeth mentally scolded herself. She'd heard the flowing water, but she had never considered she might be running headlong into it.

'Is there a bridge, or ?'

'I don't think so,' Percy said. 'And there's something wrong with the water. Listen.'

Annabeth concentrated. Within the roaring current, thousands of voices cried out shrieking in agony, pleading for mercy.

Help! they groaned. It was an accident!

The pain! their voices wailed. Make it stop!

Annabeth didn't need her eyes to imagine the river a black briny current filled with tortured souls being swept deeper and deeper into Tartarus.

'The River Acheron,' she guessed. 'The fifth river of the Underworld.'

'I liked the Phlegethon better than this,' Percy muttered.

'It's the River of Pain. The ultimate punishment for the souls of the d.a.m.ned murderers, especially.'

Murderers! the river wailed. Yes, like you!

Join us, another voice whispered. You are no better than we are.

Annabeth's head was flooded with images of all the monsters she'd killed over the years.

That wasn't murder, she protested. I was defending myself!

The river changed course through her mind showing her Zoe Nightshade, who had been slain on Mount Tamalpais because she'd come to rescue Annabeth from the t.i.tans.

She saw Nico's sister, Bianca di Angelo, dying in the collapse of the metal giant Talos because she also had tried to save Annabeth.

Michael Yew and Silena Beauregard ... who had died in the Battle of Manhattan.

You could have prevented it, the river told Annabeth. You should have seen a better way.

Most painful of all: Luke Castellan. Annabeth remembered Luke's blood on her dagger after he'd sacrificed himself to stop Kronos from destroying Olympus.

His blood is on your hands! the river wailed. There should have been another way!

Annabeth had wrestled with the same thought many times. She'd tried to convince herself Luke's death wasn't her fault. Luke had chosen his fate. Still ... she didn't know if his soul had found peace in the Underworld, or if he'd been reborn, or if he'd been washed into Tartarus because of his crimes. He might be one of the tortured voices flowing past right now.

You murdered him! the river cried. Jump in and share his punishment!

Percy gripped her arm. 'Don't listen.'

'But '

'I know.' His voice sounded as brittle as ice. 'They're telling me the same stuff. I think ... I think this moat must be the border of Night's territory. If we get across, we should be okay. We'll have to jump.'

'You said it was twenty feet!'

'Yeah. You'll have to trust me. Put your arms around my neck and hang on.'

'How can you possibly '

'There!' cried a voice behind them. 'Kill the ungrateful tourists!'

The children of Nyx had found them. Annabeth wrapped her arms around Percy's neck. 'Go!'

With her eyes closed, she could only guess how he managed it. Maybe he used the force of the river somehow. Maybe he was just scared out of his mind and charged with adrenalin. Percy leaped with more strength than she would have thought possible. They sailed through the air as the river churned and wailed below them, splashing Annabeth's bare ankles with stinging brine.

Then CLUMP. They were on solid ground again.

'You can open your eyes,' Percy said, breathing hard. 'But you won't like what you see.'

Annabeth blinked. After the darkness of Nyx, even the dim red glow of Tartarus seemed blinding.

Before them stretched a valley big enough to hold the San Francis...o...b..y. The booming noise came from the entire landscape, as if thunder were echoing from beneath the ground. Under poisonous clouds, the rolling terrain glistened purple with dark red and blue scar lines.

'It looks like ...' Annabeth fought down her revulsion. 'Like a giant heart.'

'The heart of Tartarus,' Percy murmured.

The centre of the valley was covered with a fine black fuzz of peppery dots. They were so far away, it took Annabeth a moment to realize she was looking at an army thousands, maybe tens of thousands of monsters, gathered around a central pinpoint of darkness. It was too far to see any details, but Annabeth had no doubt what the pinpoint was. Even from the edge of the valley, Annabeth could feel its power tugging at her soul.

'The Doors of Death.'

'Yeah.' Percy's voice was hoa.r.s.e. He still had the pale, wasted complexion of a corpse ... which meant he looked about as good as Annabeth felt.

She realized she'd forgotten all about their pursuers. 'What happened to Nyx ...?'

She turned. Somehow they'd landed several hundred yards from the banks of Acheron, which flowed through a channel cut into black volcanic hills. Beyond that was nothing but darkness.

No sign of anyone coming after them. Apparently even the minions of Night didn't like to cross the Acheron.

She was about to ask Percy how he had jumped so far when she heard the skittering of a rockslide in the hills to their left. She drew her drakon-bone sword. Percy raised Riptide.

A patch of glowing white hair appeared over the ridge, then a familiar grinning face with pure silver eyes.

'Bob?' Annabeth was so happy she actually jumped. 'Oh my G.o.ds!'

'Friends!' The t.i.tan lumbered towards them. The bristles of his broom had been burned off. His janitor's uniform was slashed with new claw marks, but he looked delighted. On his shoulder, Small Bob the kitten purred almost as loudly as the pulsing heart of Tartarus.

'I found you!' Bob gathered them both in a rib-crushing hug. 'You look like smoking dead people. That is good!'

'Urf,' Percy said. 'How did you get here? Through the Mansion of Night?'

'No, no.' Bob shook his head adamantly. 'That place is too scary. Another way only good for t.i.tans and such.'

'Let me guess,' Annabeth said. 'You went sideways.'

Bob scratched his chin, evidently at a loss for words. 'Hmm. No. More ... diagonal.'

Annabeth laughed. Here they were at the heart of Tartarus, facing an impossible army she would take any comfort she could get. She was ridiculously glad to have Bob the t.i.tan with them again.

She kissed his immortal nose, which made him blink.

'We stay together now?' he asked.

'Yes,' Annabeth agreed. 'Time to see if this Death Mist works.'

'And if it doesn't ...' Percy stopped himself.

There was no point in wondering about that. They were about to march into the middle of an enemy army. If they were spotted, they were dead.

Despite that, Annabeth managed a smile. Their goal was in sight. They had a t.i.tan with a broom and a very loud kitten on their side. That had to count for something.

'Doors of Death,' she said, 'here we come.'

LVII.

JASON.

JASON WASN'T SURE WHAT TO HOPE FOR: storm or fire.

As he waited for his daily audience with the lord of the South Wind, he tried to decide which of the G.o.d's personalities, Roman or Greek, was worse. But after five days in the palace he was only certain about one thing: he and his crew were unlikely to get out of here alive.

He leaned against the balcony rail. The air was so hot and dry it sucked the moisture right out of his lungs. Over the last week, his skin had got darker. His hair had turned as white as corn silk. Whenever he glanced in the mirror, he was startled by the wild, empty look in his eyes, as if he'd gone blind wandering in the desert.

A hundred feet below, the bay glittered against a crescent of red sand beach. They were somewhere on the northern coast of Africa. That's as much as the wind spirits would tell him.

The palace itself stretched out on either side of him a honeycomb of halls and tunnels, balconies, colonnades and cavernous rooms carved into the sandstone cliffs, all designed for the wind to blow through and make as much noise as possible. The constant pipe-organ sounds reminded Jason of the floating lair of Aeolus, back in Colorado, except here the winds seemed in no hurry.

Which was part of the problem.

On their best days, the southern venti were slow and lazy. On their worst days, they were gusty and angry. They'd initially welcomed the Argo II, since any enemy of Boreas was a friend of the South Wind, but they seemed to have forgotten that the demiG.o.ds were their guests. The venti had quickly lost interest in helping to repair the ship. Their king's mood got worse every day.

Down at the dock, Jason's friends were working on the Argo II. The main sail had been repaired, the rigging replaced. Now they were mending the oars. Without Leo, none of them knew how to repair the more complicated parts of the ship, even with the help of Buford the table and Festus (who was now permanently activated thanks to Piper's charmspeak and none of them understood that). But they kept trying.

Hazel and Frank stood at the helm, tinkering with the controls. Piper relayed their commands to Coach Hedge, who was hanging over the side of the ship, banging out dents in the oars. Hedge was well suited for banging on things.

They didn't seem to be making much progress, but, considering what they'd been through, it was a miracle the ship was in one piece.

Jason shivered when he thought about Khione's attack. He'd been rendered helpless frozen solid not once but twice, while Leo was blasted into the sky and Piper was forced to save them all single-handedly.

Thank the G.o.ds for Piper. She considered herself a failure for not having stopped the wind bomb from exploding, but the truth was she'd saved the entire crew from becoming ice sculptures in Quebec.

She'd also managed to direct the explosion of the icy sphere so, even though the ship had been pushed halfway across the Mediterranean, it had sustained relatively minor damage.

Down at the dock, Hedge yelled, 'Try it now!'

Hazel and Frank pulled some the levers. The port oars went crazy, chopping up and down and doing the wave. Coach Hedge tried to dodge, but one smacked him in the rear and launched him into the air. He came down screaming and splashed into the bay.

Jason sighed. At this rate, they'd never be able to sail, even if the southern venti allowed them to. Somewhere in the north, Reyna was flying towards Epirus, a.s.suming she'd got his note at Diocletian's Palace. Leo was lost and in trouble. Percy and Annabeth ... well, best-case scenario they were still alive, making their way to the Doors of Death. Jason couldn't let them down.

A rustling sound made him turn. Nico di Angelo stood in the shadow of the nearest column. He'd shed his jacket. Now he just wore his black T-shirt and black jeans. His sword and the sceptre of Diocletian hung on either side of his belt.

Days in the hot sun hadn't tanned his skin. If anything, he looked paler. His dark hair fell over his eyes. His face was still gaunt, but he was definitely in better shape than when they'd left Croatia. He had regained enough weight not to look starved. His arms were surprisingly taut with muscles, as if he'd spent the past week sword fighting. For all Jason knew, he'd been slipping off to practise raising spirits with Diocletian's sceptre, then sparring with them. After their expedition in Split, nothing would surprise him.

'Any word from the king?' Nico asked.

Jason shook his head. 'Every day, he calls for me later and later.'

'We need to leave,' Nico said. 'Soon.'

Jason had been having the same feeling, but hearing Nico say it made him even edgier. 'You sense something?'

'Percy is close to the Doors,' Nico said. 'He'll need us if he's going to make it through alive.'

Jason noticed that he didn't mention Annabeth. He decided not to bring that up.

'All right,' Jason said. 'But if we can't repair the ship '

'I promised I'd lead you to the House of Hades,' Nico said. 'One way or another, I will.'

'You can't shadow-travel with all of us. And it will take all of us to reach the Doors of Death.'

The orb at the end of Diocletian's sceptre glowed purple. Over the past week, it seemed to have aligned itself to Nico di Angelo's moods. Jason wasn't sure that was a good thing.