Dr Thorn glared at us. I decided one of his eyes had to be fake. The brown one? The blue one? He looked like he wanted to pitch us off the castle’s highest tower, but then Mrs Gottschalk said dreamily, ‘Yes, the punch is excellent. Now run along, all of you. You are not to leave the gymnasium again!’

  We didn’t wait to be told twice. We left with a lot of ‘Yes, ma’ams’ and ‘Yes, sirs’ and a couple of salutes, just because it seemed like the thing to do.

  Grover hustled us down the hall in the direction of the music.

  I could feel the teachers’ eyes on my back, but I walked closely to Thalia and asked in a low voice, ‘How did you do that finger-snap thing?’

  ‘You mean the Mist? Hasn’t Chiron shown you how to do that yet?’

  An uncomfortable lump formed in my throat. Chiron was our head trainer at camp, but he’d never shown me anything like that. Why had he shown Thalia and not me?

  Grover hurried us to a door that had gym written on the glass. Even with my dyslexia, I could read that much.

  ‘That was close!’ Grover said. ‘Thank the gods you got here!’

  Annabeth and Thalia both hugged Grover. I gave him a big high five.

  It was good to see him after so many months. He’d got a little taller and had sprouted a few more whiskers, but otherwise he looked like he always did when he passed for human – a red cap on his curly brown hair to hide his goat horns, baggy jeans and trainers with fake feet to hide his furry legs and hooves. He was wearing a black T-shirt that took me a few seconds to read. It said WESTOVER HALL: GRUNT, I wasn’t sure whether that was, like, Grover’s rank or maybe just the school motto.

  ‘So what’s the emergency?’ I asked.

  Grover took a deep breath. ‘I found two.’

  ‘Two half-bloods?’ Thalia asked, amazed. ‘Here?’

  Grover nodded.

  Finding one half-blood was rare enough. This year, Chiron had put the satyrs on emergency overtime and sent them all over the country, scouring schools from fourth grade through high school for possible recruits. These were desperate times. We were losing campers. We needed all the new fighters we could find. The problem was, there just weren’t that many demigods out there.

  ‘A brother and a sister,’ he said. ‘They’re ten and twelve. I don’t know their parentage, but they’re strong. We’re running out of time, though. I need help.’

  ‘Monsters?’

  ‘One.’ Grover looked nervous. ‘He suspects. I don’t think he’s positive yet, but this is the last day of term. I’m sure he won’t let them leave campus without finding out. It may be our last chance! Every time I try to get close to them, he’s always there, blocking me. I don’t know what to do!’

  Grover looked at Thalia desperately. I tried not to feel upset by that. Grover used to look to me for answers, but Thalia had seniority. Not just because her dad was Zeus. Thalia had more experience than any of us with fending off monsters in the real world.

  ‘Right,’ she said. ‘These half-bloods are at the dance?’

  Grover nodded.

  ‘Then let’s dance,’ Thalia said. ‘Who’s the monster?’

  ‘Oh,’ Grover said, and looked around nervously. ‘You just met him. The vice-principal, Dr Thorn.’

  Weird thing about military schools: the kids go absolutely nuts when there’s a special event and they get to be out of uniform. I guess it’s because everything’s so strict the rest of the time, they feel like they’ve got to overcompensate or something.

  There were black and red balloons all over the gym floor, and guys were kicking them in each other’s faces, or trying to strangle each other with the crêpe-paper streamers taped to the walls. Girls moved around in football huddles, the way they always do, wearing lots of makeup and spaghetti-strap tops and brightly coloured trousers and shoes that looked like torture devices. Every once in a while they’d surround some poor guy like a pack of piranhas, shrieking and giggling, and when they finally moved on, the guy would have ribbons in his hair and a bunch of lipstick graffiti all over his face. Some of the older guys looked more like me – uncomfortable, hanging out at the edges of the gym and trying to hide, like any minute they might have to fight for their lives. Of course, in my case, it was true…

  ‘There they are.’ Grover nodded towards a couple of younger kids arguing in the bleachers. ‘Bianca and Nico di Angelo.’

  The girl wore a floppy green cap, like she was trying to hide her face. The boy was obviously her little brother. They both had dark silky hair and olive skin, and they used their hands a lot as they talked. The boy was shuffling some kind of trading cards. His sister seemed to be scolding him about something. She kept looking around like she sensed something was wrong.

  Annabeth said, ‘Do they… I mean, have you told them?’

  Grover shook his head. ‘You know how it is. That could put them in more danger. Once they realize who they are, their scent becomes stronger.’

  He looked at me, and I nodded. I’d never really understood what half-bloods ‘smell’ like to monsters and satyrs, but I knew that your scent could get you killed. And the more powerful a demigod you became, the more you smelled like a monster’s lunch.

  ‘So let’s grab them and get out of here,’ I said.

  I started forward, but Thalia put her hand on my shoulder. The vice-principal, Dr Thorn, had slipped out of a doorway near the bleachers and was standing near the di Angelo siblings. He nodded coldly in our direction. His blue eye seemed to glow.

  Judging from his expression, I guessed Thorn hadn’t been fooled by Thalia’s trick with the Mist after all. He suspected who we were. He was just waiting to see why we were here.

  ‘Don’t look at the kids,’ Thalia ordered. ‘We have to wait for a chance to get them. We need to pretend we’re not interested in them. Throw him off the scent.’

  ‘How?’

  ‘We’re three powerful half-bloods. Our presence should confuse him. Mingle. Act natural. Do some dancing. But keep an eye on those kids.’

  ‘Dancing?’ Annabeth asked.

  Thalia nodded. She cocked her ear to the music and made a face. ‘Ugh. Who chose the Jesse McCartney?’

  Grover looked hurt. ‘I did.’

  ‘Oh my gods, Grover. That is so lame. Can’t you play, like, Green Day or something?’

  ‘Green who?’

  ‘Never mind. Let’s dance.’

  ‘But I can’t dance!’

  ‘You can if I’m leading,’ Thalia said. ‘Come on, goat boy.’

  Grover yelped as Thalia grabbed his hand and led him onto the dance floor.

  Annabeth smiled.

  ‘What?’ I asked.

  ‘Nothing. It’s just cool to have Thalia back.’

  Annabeth had grown taller than me since last summer, which I found kind of disturbing. She used to wear no jewellery except for her Camp Half-Blood bead necklace, but now she wore little silver earrings shaped like owls – the symbol of her mother, Athena. She pulled off her ski cap, and her long blonde hair tumbled down her shoulders. It made her look older, for some reason.

  ‘So…’ I tried to think of something to say. Act natural, Thalia had told us. When you’re a half-blood on a dangerous mission, what the heck is natural? ‘Um, design any good buildings lately?’

  Annabeth’s eyes lit up, the way they always did when she talked about architecture. ‘Oh my gods, Percy. At my new school, I get to take 3-D design, and there’s this cool computer program…’

  She went on to explain how she’d designed this huge monument that she wanted to build at Ground Zero in Manhattan. She talked about structural supports and facades and stuff, and I tried to listen. I knew she wanted to be a super architect when she grew up – she loves maths and historical buildings and all that – but I hardly understood a word she was saying.

  The truth was I was kind of disappointed to hear that she liked her new school so much. It was the first time she’d gone to school in New York. I’d been hoping to see her more o
ften. It was a boarding school in Brooklyn, which she and Thalia were both attending, close enough to Camp Half-Blood that Chiron could help if they got into any trouble. Because it was an all-girls school, and I was going to MS-54 in Manhattan, I hardly ever saw them.

  ‘Yeah, uh, cool,’ I said. ‘So you’re staying there the rest of the year, huh?’

  Her face got dark. ‘Well, maybe, if I don’t –’

  ‘Hey!’ Thalia called to us. She was slow dancing with Grover, who was tripping all over himself, kicking Thalia in the shins, and looking like he wanted to die. At least his feet were fake. Unlike me, he had an excuse for being clumsy.

  ‘Dance, you guys!’ Thalia ordered. ‘You look stupid just standing there.’

  I looked nervously at Annabeth, then at the groups of girls who were roaming the gym.

  ‘Well?’ Annabeth said.

  ‘Um, who should I ask?’

  She punched me in the gut. ‘Me, Seaweed Brain.’

  ‘Oh. Oh, right.’

  So we went onto the dance floor, and I looked over to see how Thalia and Grover were doing things. I put one hand on Annabeth’s hip, and she clasped my other hand like she was about to judo throw me.

  ‘I’m not going to bite,’ she told me. ‘Honestly, Percy. Don’t you guys have dances at your school?’

  I didn’t answer. The truth was we did. But I’d never, like, actually danced at one. I was usually one of the guys playing basketball in the corner.

  We shuffled around for a few minutes. I tried to concentrate on little things, like the crêpe-paper streamers and the punch bowl – anything but the fact that Annabeth was taller than me, and my hands were sweaty and probably gross, and I kept stepping on her toes.

  ‘What were you saying earlier?’ I asked. ‘Are you having trouble at school or something?’

  She pursed her lips. ‘It’s not that. It’s my dad.’

  ‘Uh-oh.’ I knew Annabeth had a rocky relationship with her father. ‘I thought it was getting better with you two. Is it your stepmom again?’

  Annabeth sighed. ‘He decided to move. Just when I was getting settled in New York, he took this stupid new job researching for a World War I book. In San Francisco.’

  She said this the same way she might say Fields of Punishment or Hades’s gym shorts.

  ‘So he wants you to move out there with him?’ I asked.

  ‘To the other side of the country,’ she said miserably. ‘And half-bloods can’t live in San Francisco. He should know that.’

  ‘What? Why not?’

  Annabeth rolled her eyes. Maybe she thought I was kidding. ‘You know. It’s right there.’

  ‘Oh,’ I said. I had no idea what she was talking about, but I didn’t want to sound stupid. ‘So… you’ll go back to living at camp or what?’

  ‘It’s more serious than that, Percy. I… I probably should tell you something.’

  Suddenly she froze. ‘They’re gone.’

  ‘What?’

  I followed her gaze. The bleachers. The two half-blood kids, Bianca and Nico, were no longer there. The door next to the bleachers was wide open. Dr Thorn was nowhere in sight.

  ‘We have to get Thalia and Grover!’ Annabeth looked around frantically. ‘Oh, where’d they dance off to? Come on!’

  She ran through the crowd. I was about to follow when a mob of girls got in my way. I manoeuvred round them to avoid getting the ribbon-and-lipstick treatment, and by the time I was free Annabeth had disappeared. I turned, looking for her or Thalia and Grover. Instead, I saw something that chilled my blood.

  About fifteen metres away, lying on the gym floor, was a floppy green cap just like the one Bianca di Angelo had been wearing. Near it were a few scattered trading cards. Then I caught a glimpse of Dr Thorn. He was hurrying out a door at the opposite end of the gym, steering the di Angelo kids by the scruffs of their necks, like kittens.

  I still couldn’t see Annabeth, but I knew she’d be heading the other way, looking for Thalia and Grover.

  I almost ran after her, and then I thought, Wait.

  I remembered what Thalia had said to me in the entry hall, looking at me all puzzled when I asked about the finger-snap trick: Hasn’t Chiron shown you how to do that yet? I thought about the way Grover had turned to her, expecting her to save the day.

  Not that I resented Thalia. She was cool. It wasn’t her fault her dad was Zeus and she got all the attention… Still, I didn’t need to run after her to solve every problem. Besides, there wasn’t time. The di Angelos were in danger. They might be long gone by the time I found my friends. I knew monsters. I could handle this myself.

  I took Riptide out of my pocket and ran after Dr Thorn.

  The door led into a dark hallway. I heard sounds of scuffling up ahead, then a painful grunt. I uncapped Riptide.

  The pen grew in my hands until I held a bronze Greek sword about a metre long with a leather-bound grip. The blade glowed faintly, casting a golden light on the rows of lockers.

  I jogged down the corridor, but when I got to the other end, no one was there. I opened a door and found myself back in the main entry hall. I had gone full circle. I didn’t see Dr Thorn anywhere, but there on the opposite side of the room were the di Angelo kids. They stood frozen in horror, staring right at me.

  I advanced slowly, lowering the tip of my sword. ‘It’s okay. I’m not going to hurt you.’

  They didn’t answer. Their eyes were full of fear. What was wrong with them? Where was Dr Thorn? Maybe he’d sensed the presence of Riptide and retreated. Monsters hated celestial bronze weapons.

  ‘My name’s Percy,’ I said, trying to keep my voice level. ‘I’m going to take you out of here, get you somewhere safe.’

  Bianca’s eyes widened. Her fists clenched. Only too late did I realize what her look meant. She wasn’t afraid of me. She was trying to warn me.

  I whirled round and something went WHIIISH! Pain exploded in my shoulder. A force like a huge hand yanked me backwards and slammed me to the wall.

  I slashed with my sword but there was nothing to hit.

  A cold laugh echoed through the hall.

  ‘Yes, Perseus Jackson,’ Dr Thorn said. His accent mangled the J in my last name. ‘I know who you are.’

  I tried to free my shoulder. My coat and shirt were pinned to the wall by some kind of spike – a black daggerlike projectile about half a metre long. It had grazed the skin of my shoulder as it passed through my clothes, and the cut burned. I’d felt something like this before. Poison.

  I forced myself to concentrate. I would not pass out.

  A dark silhouette now moved towards us. Dr Thorn stepped into the dim light. He still looked human, but his face was ghoulish. He had perfect white teeth and his brown/blue eyes reflected the light of my sword.

  ‘Thank you for coming out of the gym,’ he said. ‘I hate middle-school dances.’

  I tried to swing my sword again, but he was just out of reach.

  WHIIIISH! A second projectile shot from somewhere behind Dr Thorn. He didn’t appear to move. It was as if someone invisible were standing behind him, throwing knives.

  Next to me, Bianca yelped. The second thorn impaled itself in the stone wall, a millimetre from her face.

  ‘All three of you will come with me,’ Dr Thorn said. ‘Quietly. Obediently. If you make a single noise, if you call out for help or try to fight, I will show you just how accurately I can throw.’

  2 The Vice-Principal Gets A Missile Launcher

  I didn’t know what kind of monster Dr Thorn was, but he was fast.

  Maybe I could defend myself if I could get my shield activated. All that it would take was a touch of my wristwatch. But defending the di Angelo kids was another matter. I needed help, and there was only one way I could think to get it.

  I closed my eyes.

  ‘What are you doing, Jackson?’ hissed Dr Thorn. ‘Keep moving!’

  I opened my eyes and kept shuffling forward. ‘It’s my shoulder,’ I lied, trying to sound m
iserable, which wasn’t hard. ‘It burns.’

  ‘Bah! My poison causes pain. It will not kill you. Walk!’

  Thorn herded us outside, and I tried to concentrate. I pictured Grover’s face. I focused on my feelings of fear and danger. Last summer, Grover had created an empathy link between us. He’d sent me visions in my dreams to let me know when he was in trouble. As far as I knew, we were still linked, but I’d never tried to contact Grover before. I didn’t even know if it would work while Grover was awake.

  Hey, Grover! I thought. Thorn’s kidnapping us! He’s a poisonous spike-throwing maniac! Help!

  Thorn marched us into the woods. We took a snowy path dimly lit by old-fashioned lamplights. My shoulder ached. The wind blowing through my ripped clothes was so cold that I felt like a Percysicle.

  ‘There is a clearing ahead,’ Thorn said. ‘We will summon your ride.’

  ‘What ride?’ Bianca demanded. ‘Where are you taking us?’

  ‘Silence, you insufferable girl!’

  ‘Don’t talk to my sister that way!’ Nico said. His voice quavered, but I was impressed that he had the guts to say anything at all.

  Dr Thorn made a growling sound that definitely wasn’t human. It made the hairs on the back of my neck stand up, but I forced myself to keep walking and pretend I was being a good little captive. Meanwhile, I projected my thoughts like crazy – anything to get Grover’s attention: Grover! Apples! Tin cans! Get your furry goat behind out here and bring some heavily armed friends!

  ‘Halt,’ Thorn said.

  The woods had opened up. We’d reached a cliff overlooking the sea. At least, I sensed the sea was down there, about a hundred metres below. I could hear the waves churning and I could smell the cold salty froth. But all I could see was mist and darkness.

  Dr Thorn pushed us towards the edge. I stumbled, and Bianca caught me.

  ‘Thanks,’ I murmured.

  ‘What is he?’ she whispered. ‘How do we fight him?’

  ‘I… I’m working on it.’

  ‘I’m scared,’ Nico mumbled. He was fiddling with something – a little metal toy soldier of some kind.