My day started normal. Or as normal as it ever gets at Meriwether College Prep.

See, it's this "progressive" school in downtown Manhattan, which means we sit on beanbag chairs instead of at desks, and we don't get grades, and the teachers wear jeans and rock concert T-shirts to work.

That's all cool with me. I mean, I'm ADHD and dyslexic, like most half-bloods, so I'd never done that great in regular schools even before they kicked me out. The only bad thing about Meriwether was that the teachers always looked on the bright side of things, and the kids weren't always ... well, bright.

Take my first class today: English. The whole middle school had read this book called Lord of the Flies, where all these kids get marooned on an island and go psycho. So for our final exam, our teachers sent us into the break yard to spend an hour with no adult supervision to see what would happen. What happened was a massive wedgie contest between the seventh and eighth graders, two pebble fights, and a full-tackle basketball game. The school bully, Matt Sloan, led most of those activities.

Sloan wasn't big or strong, but he acted like he was. He had eyes like a pit bull, and shaggy black hair, and he always dressed in expensive but sloppy clothes, like he wanted everybody to see how little he cared about his family's money. One of his front teeth was chipped from the time he'd taken his daddy's Porsche for a joyride and run into a PLEASE SLOW DOWN FOR CHILDREN sign.

Anyway, Sloan was giving everybody wedgies until he made the mistake of trying it on my friend Tyson.

Tyson was the only homeless kid at Meriwether College Prep. As near as I could figure, he'd been abandoned by his parents when he was very young, probably because he was so ... different. He was six-foot-three and built like the Abominable Snowman, but he cried a lot and was scared of just about everything, including his own reflection. His face was kind of misshapen and brutal-looking. I couldn't tell you what colour his eyes were, because I could never make myself look higher than his crooked teeth. His voice was deep, but he talked funny, like a much younger kid-I guess because he'd never gone to school before coming to Meriwether. He wore tattered jeans, grimy size-twenty sneakers, and a plaid flannel shirt with holes in it. He smelled like a New York City alleyway, because that's where he lived, in a cardboard refrigerator box off 72nd Street.

Meriwether Prep had adopted him as a community service project so all the students could feel good about themselves. Unfortunately, most of them couldn't stand Tyson. Once they discovered he was a big softie, despite his massive strength and his scary looks, they made themselves feel good by picking on him. I was pretty much his only friend, which meant he was my only friend.

Anyway, Matt Sloan snuck up behind him and tried to give him a wedgie, and Tyson panicked. He swatted Sloan away a little too hard. Sloan flew fifteen feet and got tangled in the little kids' tire swing.

"You freak!" Sloan yelled. "Why don't you go back to your cardboard box!'

Tyson started sobbing. He sat down on the jungle gym so hard he bent the bar, and buried his head in his hands.

"Take it back, Sloan!" I shouted.

Sloan just sneered at me. "Why do you even bother, Jackson? You might have friends if you weren't always stick-ing up for that freak."

I balled my fists. I wanted to punch his silly face, but Luke told me not to draw attention to myself. That isn't ending well. "He's not a freak. He's just..."

I tried to think of the right thing to say, but Sloan wasn't listening. He and his big ugly friends were too busy laughing. I wondered if it were my imagination, or if Sloan had more goons hanging around him than usual. I was used to seeing him with two or three, but today he had like, half a dozen more, and I was pretty sure I'd never seen them before.

"Just wait till PE, Jackson," Sloan called. "You are so dead."

When first period ended, our English teacher, Mr. de Milo, came outside to inspect the carnage. He pronounced that we'd understood Lord of the Flies perfectly.

We all passed his course, and we should never, never grow up to be violent people.

Matt Sloan nodded earnestly, then gave me a chip-toothed grin.

I had to promise to buy Tyson an extra peanut butter sandwich at lunch to get him to stop sobbing.

"I... I am a freak?" he asked me.

"No," I promised, gritting my teeth. "Matt Sloan is the freak.'

Tyson sniffled. 'You are a good friend. Miss you next year if ... if I can't...' His voice trembled. I realized he didn't know if he'd be invited back next year for the community service project. I wondered if the headmaster had even bothered talking to him about it.

"Don't worry, big guy,' I managed. Everything's going to be fine.'

Tyson gave me such a grateful look I felt like a big liar. How could I promise a kid like him that anything would be fine?

Our next exam was science. Mrs Tesla told us that we had to mix chemicals until we succeeded in making something explode. Tyson was my lab partner. His hands were way too big for the tiny vials we were supposed to use. He accidentally knocked a tray of chemicals off the counter and made an orange mushroom cloud in the trashcan.

After Mrs Tesla evacuated the lab and called the hazardous waste removal squad, she praised Tyson and me for being natural chemists. We were the first ones who'd ever aced her exam in under thirty seconds.

I was glad the morning went fast, because it kept me from thinking too much about my problems. I couldn't stand the idea that something might be wrong at camp. Even worse, I couldn't shake the memory of my bad dream. I had a terrible feeling that Grover was in danger.

In social studies, while we were drawing latitude/longitude maps, I opened my notebook and stared at the photo inside - me, Annabeth and Grover at Camp Half-Blood. Grover's Rasta hat was covering his curly hair, and he looked like he was laughing. I was in the middle, grinning like crazy, my arms over both of them. And then there was Annabeth. Her curly blonde hair was pulled into a ponytail, but strands of them covered her face. She was beaming, and all three of us were wearing the orange Camp Half-Blood t-shirts. I sighed. Sure, hanging out with Luke was great, and training was fun, but I missed my old friends. I missed camp. I missed Grover's nervous chewing, and his bleating laugh. I missed the Stolls' constant pranking, or Chiron's wise words. I missed talking to Annabeth, and her nicknames for me or her know-it-all expression. I missed the sweet smell of the strawberry fields, and playing Capture the Flag every Friday.

I was about to close my notebook when Matt Sloan reached over and ripped the photo out of the rings.

'Hey!' I protested.

Sloan checked out the picture and his eyes got wide. 'No way, Jackson. Who is that? She is not your –'

'Give it back!' My ears felt hot.

Sloan handed the photo to his ugly buddies, who snickered and started ripping it up to make spit wads. They were new kids who must've been visiting, because they were all wearing those stupid HI! MY NAME IS: tags from the admissions office. They must've had a weird sense of humour, too, because they'd all filled in strange names like: MARROW SUCKER, SKULL EATER and JOE BOB.

No human beings had names like that.

"These guys are moving here next year,' Sloan bragged, like that was supposed to scare me. I bet they can pay the tuition, too, unlike your retard friend.'

'He's not retarded.' I had to try really, really hard not to punch Sloan in the face.

'You're such a loser, Jackson. Good thing I'm gonna put you out of your misery next period.'

His huge buddies chewed up my photo. I wanted to pulverize them, but I was under strict orders from Luke to not draw attention to myself. And, I would've felt bad if they had to pull my mom out of her work. I had caused enough trouble.

Still, part of me thought, if Sloan only knew who I really was...

The bell rang.

As Tyson and I were leaving class, a girl's voice whispered, 'Percy!' I looked around the locker area, but nobody was paying me any attention.

Like any girl at Meriwether would ever be caught dead calling my name.

Before I had time to consider whether or not I'd been imagining things, a crowd of kids rushed for the gym, carrying Tyson and me along with them. It was time for PE. Our coach had promised us a free-for-all dodgeball game, and Matt Sloan had promised to kill me.

The gym uniform at Meriwether is sky-blue shorts and tie-dyed T-shirts. Fortunately, we did most of our athletic stuff inside, so we didn't have to jog through Tribeca looking like a bunch of boot-camp hippie children.

I changed as quickly as I could in the locker room because I didn't want to deal with Sloan. I was about to leave when Tyson called, 'Percy?'

He hadn't changed yet. He was standing by the weight-room door, clutching his gym clothes. 'Will you ... uh...'

'Oh. Yeah.' I tried not to sound aggravated about it. 'Yeah, sure, man.'

Tyson ducked inside the weight room. I stood guard outside the door while he changed. I felt kind of awkward doing this, but he asked me to most days. I think it's because he's completely hairy and he's got weird scars on his back that I've never had the courage to ask him about.

Anyway, I'd learned the hard way that if people teased Tyson while he was dressing, he'd get upset and start ripping the doors off lockers.

When we got into the gym, Coach Nunley was sitting at his little desk reading Sports Illustrated. Nunley was about a million years old, with bifocals and no teeth and a greasy wave of grey hair. He reminded me of the old Oracle at Camp Half-Blood - which was a shrivelled-up mummy - except Coach Nunley moved a lot less and he never billowed green smoke. Well, at least not that I'd observed.

Matt Sloan said, 'Coach, can I be captain?'

'Eh?' Coach Nunley looked up from his magazine. 'Yeah,' he mumbled. 'Mm-hmm.'

Sloan grinned and took charge of the picking. He made me the other team's captain, but it didn't matter who I picked, because all the jocks and the popular kids moved over to Sloan's side. So did the big group of visitors.

On my side I had Tyson, Corey Bailer the computer geek, Raj Mandali the calculus whiz, and a half-dozen other kids who always got harassed by Sloan and his gang. Normally I would've been okay with just Tyson - he was worth half a team all by himself - but the visitors on Sloan's team were almost as tall and strong-looking as Tyson, and there were six of them.

Matt Sloan spilled a cage full of balls in the middle of the gym.

"Scared,' Tyson mumbled. "Smell funny.'

I looked at him. 'What smells funny?' Because I didn't figure he was talking about himself.

'Them.' Tyson pointed at Sloan's new friends. "Smell funny.'

The visitors were cracking their knuckles, eyeing us like it was slaughter time.

I couldn't help wondering where they were from. Someplace where they fed kids raw meat and beat them with sticks.

Sloan blew the coach's whistle and the game began. Sloan's team ran for the centre line. On my side, Raj Mandali yelled something in Urdu, probably 'I have to go potty!' and ran for the exit. Corey Bailer tried to crawl behind the wall mat and hide. The rest of my team did their best to cower in fear and not look like targets.

"Tyson,' I said. 'Let's g-'

A ball slammed into my gut. I sat down hard in the middle of the gym floor.

The other team exploded in laughter.

My eyesight was fuzzy. I felt like I'd just got the Heimlich manoeuvre from a gorilla. I couldn't believe anybody could throw that hard.

Tyson yelled, 'Percy, duck!'

I rolled as another dodgeball whistled past my ear at the speed of sound. Whooom!

It hit the wall mat, and Corey Bailer yelped.

'Hey!' I yelled at Sloan's team. 'You could kill somebody!'

The visitor named Joe Bob grinned at me evilly. Somehow, he looked a lot

bigger now ... even taller than Tyson. His biceps bulged beneath his T-shirt. 'I hope so, Perseus Jackson! I hope so!'

The way he said my name sent a chill down my back. Nobody called me Perseus except those who knew my true identity. Friends ... and enemies.

What had Tyson said? They smell funny.

Monsters.

All around Matt Sloan, the visitors were growing in size. They were no longer kids. They were two-and-a-half-metre-tall giants with wild eyes, pointy teeth and hairy arms tattooed with snakes and hula women and Valentine hearts.

Matt Sloan dropped his ball. 'Whoa! You're not from Detroit! Who...'

The other kids on his team started screaming and backing towards the exit, but the giant named Marrow Sucker threw a ball with deadly accuracy. It streaked past Raj Mandali just as he was about to leave and hit the door, slamming it shut like magic. Raj and some of the other kids banged on it desperately but it wouldn't budge.

'Let them go!' I yelled at the giants.

The one called Joe Bob growled at me. He had a tattoo on his biceps that said: JB luvs Babycakes. 'And lose our tasty morsels? No, Son of the Sea God. We Laistrygonians aren't just playing for your death. We want lunch!'

He waved his hand and a new batch of dodgeballs appeared on the centre line – but these balls weren't made of red rubber. They were bronze, the size of cannon balls, perforated like Wiffle balls with fire bubbling out the holes. They must've been searing hot, but the giants picked them up with their bare hands.

This was around the point that I realised that Riptide wasn't in my gym shorts. They didn't have pockets. Time to put my training to the test, I thought.

I knew they probably didn't care, but it made me irritated that they referred to me as, 'Son of the Sea God'. Even though they were throwing burning hot balls, I was indifferent. I saw red.

I charged at them, without a sword, instead calling the water from inside me. I dodged all the balls they threw at me, and kicked and punched and hit, until all of them were on the floor, groaning. I realised I had time to run to the gym changing room and grab my sword. I was at the door when I saw Matt Sloan on the ground, looking at me in horror. I didn't know what the mortals could see because of the mist, but I hope it wasn't anything too bad. But with my luck, it probably was.

I pushed the doors open, and ran to my clothes. I switched my gym shorts for my normal pants, so that if Riptide accidentally dropped out of my hand, it would return to me.

Once I returned to the gym, all the monsters were up again, looking like they wanted to kill me. They ran at me, at the same time as I ran at them, smirking. I sliced and stabbed and whirled and dodged, until all that was left was a pile of dust. But there was one left. The biggest, ugliest, and meanest one. I tried to stab him, but it had little effect on him. Alright, I said to myself. Plan B.

I stood in front of him, took a deep breath and tried something I had never tried before.

Blood-bending.

Since Poseidon was God of the Sea, and not of all liquids, I was skeptical of this working. But Luke insisted I try it at least once.

I thrust out my hand, imagining his blood vessels popping, his throat filling up with water, and his brain exploding. Its eyes widened in pain, and then the blood burst out of him. His brain exploded, just the way I wanted it to. He didn't dissolve into dust, instead stayed there like how a normal mortal would die.

I heard a gasp of terror behind me. I whirled around, ready to kill anymore monsters, until I saw someone I thought I would never see here appear. Annabeth.

She looked at me in terror and shock, looking at me like I was some kind of monster. She looked the same as she had a few months ago, but taller and she had bags under her eyes.

'P-Percy? What are you- how did you do that?'

I scowled at her, not wanting to tell her.

'Just picked up a few new things. What are you doing her, Annabeth?'

Her face hardened, and she looked at me coldly.

'I was looking for you. And, we should talk somewhere else. The mortals can hear us.'

I looked around, and realised they were staring at us. Matt Sloan's mouth was open wide.

'That's the girl... That's the girl...'

I sneered at him, causing him to fall silent. Tyson looked at me fearfully.

'Percy? Are you leaving?'

I didn't have the heart to tell him yes, so I told him I would see him later. Annabeth eyed Tyson up like he was a safety precaution.

Me and her left quickly, each too scared to look each other in the eye. We reached an alleyway, which probably wasn't the best of spots, but we had important things to talk about. Once we had made sure no one could hear or see us, she turned to me.

'Why?'

'Why what?'

'You know what I'm asking! Why did you and Luke join... join K-Kronos?' She said, and I thought I might have seen her trembling.

'Names have power. You should know that. And, plus, that's none of your business.' I glared at her. She glared straight back.

'What do you mean it's none of my business? I see you and Luke go into the woods, and then you disappear. You two were my friends, so it is my business!'

This was going to take a while.

I told her the story, and she got paler and paler, and when I told her Luke convinced me to join Kronos, she choked.

'Percy... Please... Luke may have done all that and disobeyed the gods, but you haven't done anything bad. You can still come back to camp! Still rejoin the gods! Percy, please...'

I stared at her sadly, and once she looked me in the eye, I gazed at my shoes. They were covered in monster blood. Ew.

I shook my head, and she glanced at me, her stormy grey eyes alight with anger.

She sighed.

'Well, then, I'm sorry Percy.'

She caught me off guard, and hit me with her dagger. I hadn't even noticed she'd brought it out.

I fell on the floor, my head hitting the floor. My vision swam, the world was spinning. The last thing I heard was Annabeth's regretful voice.

'This is for your own good Percy. We'll make you see sense again.'