The carnation tilted its face towards a hill on our left.

‘Up there,’ I said.

Thalia and Nico stopped. They were covered with soot from trudging through Punishment. I probably didn’t look much better.

A loud grinding noise came from the other side of the hill, like somebody was dragging a washing machine. Then the hill shook with a BOOM! BOOM! BOOM! and a man yelled curses.

Thalia looked at Nico. ‘Is that who I think it is?’

‘Afraid so,’ Nico said. ‘The number-one expert on cheating death.’

Before I could ask what he meant, he led us to the top of the hill.

The dude on the other side was not pretty, and he was not happy. He looked like one of those troll dolls with orange skin, a pot belly, scrawny legs and arms and a big loincloth/diaper thing around his waist. His ratty hair stuck up like a torch. He was hopping around, cursing and kicking a boulder that was twice as big as he was.

‘I won’t!’ he screamed. ‘No, no, no!’ Then he launched into a string of swear words in several different languages. If I’d had one of those jars where you put a quarter in for each bad word, I would’ve made around five hundred dollars.

He started to walk away from the boulder, but after three metres he lurched backwards, like some invisible force had pulled him. He staggered back to the boulder and started banging his head against it.

‘All right!’ he screamed. ‘All right, curse you!’

He rubbed his head and muttered some more swear words. ‘But this is the last time. Do you hear me?’

Nico looked at us. ‘Come on. While he’s between attempts.’

We scrambled down the hill.

‘Sisyphus!’ Nico called.

The troll guy looked up in surprise. Then he scrambled behind his rock. ‘Oh, no! You’re not fooling me with those disguises! I know you’re the Furies!’

‘We’re not the Furies,’ I said. ‘We just want to talk.’

‘Go away!’ he shrieked. ‘Flowers won’t make it better. It’s too late to apologize!’

‘Look,’ Thalia said, ‘we just want –’

‘La-la-la!’ he yelled. ‘I’m not listening!’

We played tag with him round the boulder until finally Thalia, who was the quickest, caught the old man by his hair.

‘Stop it!’ he wailed. ‘I have rocks to move. Rocks to move!’

‘I’ll move your rock!’ Thalia offered. ‘Just shut up and talk to my friends.’

Sisyphus stopped fighting. ‘You’ll – you’ll move my rock?’

‘It’s better than looking at you.’ Thalia glanced at me. ‘Be quick about it.’ Then she shoved Sisyphus towards us.

She put her shoulder against the rock and started pushing it very slowly uphill.

Sisyphus scowled at me distrustfully. He pinched my nose.

‘Ow!’ I said.

‘So you’re really not a Fury,’ he said in amazement. ‘What’s the flower for?’

‘We’re looking for someone,’ I said. ‘The flower is helping us find him.’

‘Persephone!’ He spat in the dust. ‘That’s one of her tracking devices, isn’t it?’ He leaned forward, and I caught an unpleasant whiff of old-guy-who’s-been-rolling-a-rock-for-eternity. ‘I fooled her once, you know. I fooled them all.’

I looked at Nico. ‘Translation?’

‘Sisyphus cheated death,’ Nico explained. ‘First he chained up Thanatos, the reaper of souls, so no one could die. Then when Thanatos got free and was about to kill him, Sisyphus told his wife not to do the correct funeral rites so he couldn’t rest in peace. Sisy here – May I call you Sisy?’

‘No!’

‘Sisy tricked Persephone into letting him go back to the world to haunt his wife. And he didn’t come back.’

The old man cackled. ‘I stayed alive another thirty years before they finally tracked me down!’

Thalia was halfway up the hill now. She gritted her teeth, pushing the boulder with her back. Her expression said, Hurry up!

‘So that was your punishment,’ I said to Sisyphus. ‘Rolling a boulder up a hill forever. Was it worth it?’

‘A temporary setback!’ Sisyphus cried. ‘I’ll bust out of here soon, and when I do they’ll all be sorry!’

‘How would you get out of the Underworld?’ Nico asked. ‘It’s locked down, you know.’

Sisyphus grinned wickedly. ‘That’s what the other one asked.’

My stomach tightened. ‘Someone else asked your advice?’

‘An angry young man,’ Sisyphus recalled. ‘Not very polite. Held a sword to my throat. Didn’t offer to roll my boulder at all.’

‘What did you tell him?’ Nico said. ‘Who was he?’

Sisyphus massaged his shoulders. He glanced up at Thalia, who was almost at the top of the hill. Her face was bright red and drenched in sweat.

‘Oh… it’s hard to say,’ Sisyphus said. ‘Never seen him before. He carried a long package all wrapped up in black cloth. Skis, maybe? A shovel? Maybe if you wait here, I could go look for him…’

‘What did you tell him?’ I demanded.

‘Can’t remember.’

Nico drew his sword. The Stygian iron was so cold it steamed in the hot, dry air of Punishment. ‘Try harder.’

The old man winced. ‘What kind of person carries a sword like that?’

‘A son of Hades,’ Nico said. ‘Now answer me!’

The colour drained from Sisyphus’s face. ‘I told him to talk to Melinoe! She always has a way out!’

Nico lowered his sword. I could tell the name Melinoe bothered him. ‘All right. What did this demigod look like?’

‘Um… he had a nose,’ Sisyphus said. ‘A mouth. And one eye and –’

‘One eye?’ I interrupted. ‘Did he have an eye patch?’

‘Oh… maybe,’ Sisyphus said. ‘He had hair on his head. And –’ He gasped and looked over my shoulder. ‘There he is!’

We fell for it.

As soon as we turned, Sisyphus took off. ‘I’m free! I’m free! I’m – ACK!’ Three metres from the hill, he hit the end of his invisible leash and fell on his back. Nico and I grabbed his arms and hauled him up the hill.

‘Curse you!’ He let loose with bad words in Ancient Greek, Latin, English, French and several other languages I didn’t recognize. ‘I’ll never help you! Go to Hades!’

‘Already there,’ Nico muttered.

‘Incoming!’ Thalia shouted.

I looked up and might have used a few swear words myself. The boulder was bouncing straight towards us. Nico jumped one way. I jumped the other. Sisyphus yelled, ‘NOOOOOOO!’ as the thing ploughed into him. Somehow he braced himself and stopped it before it could run him over. I guess he’d had a lot of practice.

‘Take it again!’ he wailed. ‘Please. I can’t hold it.’

‘Not again,’ Thalia gasped. ‘You’re on your own.’

He treated us to a lot more colourful language. It was clear he wasn’t going to help us any further, so we left him to his punishment.

‘Melinoe’s cave is this way,’ Nico said.

‘If this thief guy really has one eye,’ I said, ‘that could be Ethan Nakamura, son of Nemesis. He’s the one who freed Kronos.’

‘I remember,’ Nico said darkly. ‘But if we’re dealing with Melinoe, we’ve got bigger problems. Come on.’

As we walked away, Sisyphus was yelling, ‘All right, but this is the last time. Do you hear me? The last time!’

Thalia shuddered.

‘You okay?’ I asked her.

‘I guess…’ She hesitated. ‘Percy, the scary thing is, when I got to the top, I thought I had it. I thought, This isn’t so hard. I can get the rock to stay. And as it rolled down, I was almost tempted to try it again. I figured I could get it the second time.’

She looked back wistfully.

‘Come on,’ I told her. ‘The sooner we’re out of here the better.’

We walked for what seemed like eternity. Three more petals withered from the carnation, which meant it was now officially half dead. The flower pointed towards a range of jagged grey hills that looked like teeth, so we trudged in that direction over a plain of volcanic rock.

‘Nice day for a stroll,’ Thalia muttered. ‘The Hunters are probably feasting in some forest glade right about now.’

I wondered what my family was doing. My mom and stepdad, Paul, would be worried when I didn’t come home from school, but it wasn’t the first time this had happened. They’d figure out pretty quickly that I was on some quest. My mom would be pacing back and forth in the living room, wondering if I was going to make it back to unwrap my presents.

‘So who is this Melinoe?’ I asked, trying to take my mind off home.

‘Long story,’ Nico said. ‘Long, very scary story.’

I was about to ask what he meant when Thalia dropped to a crouch. ‘Weapons!’

I drew Riptide. I’m sure I looked terrifying with a potted carnation in the other hand, so I put it down. Nico drew his sword.

We stood back to back. Thalia notched an arrow.

‘What is it?’ I whispered.

She seemed to be listening. Then her eyes widened. A ring of a dozen daemons materialized around us.

They were part humanoid female, part bat. Their faces were pug-nosed and furry, with fangs and bulging eyes. Matted grey fur and piecemeal armour covered their bodies. They had shrivelled arms with claws for hands, leathery wings that sprouted from their backs and stubby bowed legs. They would’ve looked funny except for the murderous glow in their eyes.

‘Keres,’ Nico said.

‘What?’ I asked.

‘Battlefield spirits. They feed on violent death.’

‘Oh, wonderful,’ Thalia said.

‘Get back!’ Nico ordered the daemons. ‘The son of Hades commands you!’

The Keres hissed. Their mouths foamed. They glanced apprehensively at our weapons, but I got the feeling the Keres weren’t impressed by Nico’s command.

‘Soon Hades will be defeated,’ one of them snarled. ‘Our new master shall give us free rein!’

Nico blinked. ‘New master?’

The lead daemon lunged. Nico was so surprised it might have slashed him to bits, but Thalia shot an arrow point-blank into its ugly bat face, and the creature disintegrated.

The rest of them charged. Thalia dropped her bow and drew her knives. I ducked as Nico’s sword whistled over my head, cutting a daemon in half. I sliced and jabbed and three or four Keres exploded around me, but more just kept coming.

‘Iapetus shall crush you!’ one shouted.

‘Who?’ I asked. Then I ran her through with my sword. Note to self: if you vapourize monsters, they can’t answer your questions.

Nico was also cutting an arc through the Keres. His black sword absorbed their essence like a vacuum cleaner, and the more he destroyed, the colder the air became around him. Thalia flipped a daemon on its back, stabbed it, and impaled another one with her second knife without even turning around.