A/N: This is my first attempt at a multi-chapter or AU fanfic, so if either of those offend you, consider this fair warning! Also, T is probably pretty high for the rating, but I figured I'd err on the side of caution for now.

Special thanks for this one goes to bibliophile114, who not only acted as beta reader but also gave me the idea in the first place. So now you all know who to blame, right? (Seriously, thanks. I can't say enough how awesome you are! ...Unless everyone hates this, of course... :P)

I hope you enjoy!

Disclaimer: Aside from the plot, everything here belongs to Rick Riordan. Even though he's making us wait an entire year for the next book after ending "The Lost Hero" like that!

Chapter 1: Hydra 101

Well, this was definitely one of your classic good news, bad news situations.

The good news? After playing "Off With Your Heads" with a hydra for over an hour (the game probably wouldn't have lasted as long if I'd remembered right away hydras liked to grow heads twice as fast as I chopped them off), the hydra was officially ancient history. Well, kind of. It doesn't really count as ancient history when the monsters just re-form and go right back to trying to kill you.

But the bad news? I was now standing next to a smoking pile of rubble that used to be a high school gym. Whoops.

Still, as far as I knew, no one had been hurt, which meant I was getting better at this. When I saw the hydra was nesting in the alley behind the school, I'd sent my keeper, Grover, to evacuate all the kids. He'd told them there was some sort of bomb threat, which was usually a good cover story. And anyone looking at the gym right now was not going to argue.

Anyway, I was feeling pretty proud of myself overall. Not only was I uninjured, I'd also gotten all the mortals out of danger and only caused minor property damage. Someone was going to have to replace the water heater I'd had to blow up to dust the hydra, and of course the students were going to have to run their laps in the middle of Manhattan for awhile, but this definitely ranked as a success on Percy Jackson's List of Potential Disasters. Considering I'd just turned sixteen a couple months ago, that list was already pretty long.

I turned around to start the "fleeing the scene of the crime" part of the battle and stopped dead. Leaning casually against a streetlamp was a tall, suntanned girl with curly blond hair and steel gray eyes that matched her blazer and pleated skirt.

I cursed under my breath. She did not look happy. I wondered what she saw; I had firsthand experience with the tricks the Mist could play on mortals. Considering I still had my sword out and the wreckage behind me was still smoking, I didn't think this would end any better than last week's chimera fiasco had. (Given the highly circumstantial evidence, a lifetime ban from Chuck E. Cheese had seemed a little unreasonable.)

I put down my sword and held my hands in front of me non-threateningly. "Look, I can explain," I told the girl as calmly as I could while still looking frantically up and down the alley for any signs of police cars. Grover must have persuaded the police not to investigate the bomb threat somehow, but personal experience made me doubt he was prepared to hide an explosion. Even if he probably should have been expecting one by now. "I swear this isn't what it looks like."

"Oh, really?" the girl snorted. "It looks like you forgot hydras regenerate their non-immortal heads and were forced to finally use our school's water heater when you couldn't defend yourself anymore."

"No, that's not—wait, what?" I must have been staring at her like she had more heads than the hydra, because she rolled her eyes.

"Hydra. You. Water heater. Am I right, or am I right?"

I continued to stare. "You saw the hydra?"

She rolled her eyes again. "I think we've established that, yes. And while we're on the subject, the battle would have lasted about five minutes if you'd driven it into the furnace room of the school. Cauterize the head wounds so new ones can't grow. I suppose the burning water eventually accomplished the same feat, although that looked more like desperation to me—"

"Wait!" I said, stopping her as I finally realized what she was saying. "You saw me fighting the hydra, and you just decided to stand there and watch?"

She shrugged. "Yeah."

I started to get a little angry. "Why didn't you go get help or something? People could've gotten hurt! I could have gotten hurt!" I didn't want mortals charging into battle or anything, but what kind of person just watches as someone fights for his life? And how had I not noticed her for over an hour? I could have sworn she appeared out of thin air.

The girl just shrugged again. "The school was already evacuated, and the hydra has a limited range, so the only person in danger was you. And you dying makes my life a lot easier. It was only logical not to interfere."

"Oh, as long as it was the logical choice," I said sarcastically. "I'm so sorry to inconvenience you by staying alive. Maybe you should've helped the hydra, huh?"

"I considered that," the girl said thoughtfully, her gray eyes calculating. "But there was never a good opening."

I was sure my jaw was about two inches from the ground at this point. This girl was certifiably insane.

"Anyway," she continued, "after the first ten minutes, I figured there wasn't much point. It was pretty clear you didn't have a chance."

"Well, apparently you were wrong," I snapped.

"Yes," she said, frowning. "I overestimated the hydra's abilities."

I scowled. "Or you underestimated mine."

"No." The way she said it, so matter-of-factly, had me nodding in agreement before I caught myself. I scowled deeper. Who did this girl think she was?

Suddenly I heard sirens in the distance. The girl must have heard them too, because she muttered something like, "I thought I'd taken care of them for at least another hour." Before I could ask, though, she sighed disappointedly. "You should probably run now."

My scowl melted into a grin. "What, upset you don't get to spend more time with me? I didn't know you cared."

I have no idea where she'd been concealing it, but suddenly the girl had a wicked-looking bronze knife pointed at my chest. It looked like the same material as my sword, but there was no way this girl could have access to celestial bronze. …Right? Either way, I was suddenly regretting dropping my sword so early.

"Let's be clear: I will never care about you," she spat at me. "I'm only upset I don't have time to kill you before the police arrive. Now I have to wait and kill you later. I don't like to procrastinate."

"…And you're sure you're in high school?" I asked.

She rolled her eyes yet again and glanced pointedly at the ruined gym behind me. "No thanks to you. And if my drafting table isn't exactly as I left it, I will personally hunt you down and chop off your head."

And with that promise, she turned and sprinted down the street in front of the school.

I stood in shock for a moment. I'd ticked off girls before, sure, but so far they'd stopped short of actively promising my death by bronze knife. It was too bad the blond girl was so nuts. She'd been pretty cute for a psychopath.

The sounds of the approaching sirens broke into my thoughts and reminded me I had some running of my own to do. I'd have to ask my dad about the mysterious blond girl later. I jumped the chain-link fence at the end of the alley and took off.

When I finally got back to our rendezvous point, Grover was already there. The rendezvous point was a foreclosed business just east of the hydra's nest, and he was currently pacing awkwardly in front of the "Sorry, we're closed!" sign in the window. He must have been worried too, because he was gnawing on an empty Coke can despite being in full view of any mortals wandering past the deserted store.

"Hey, G-man, what's up?" I asked nonchalantly, strolling up behind him. He yelped and jumped a full foot in the air, dislodging one of his shoes and exposing his natural hoof. I glanced around quickly to make sure no one was watching us. Most people ignored Grover chomping on cans, but his hooves were a little harder to explain. That's how I'd found out Grover was a satyr in the first place, back when I was seven. Of course, that would have been a little more shocking if it hadn't come right after finding out my dad was an ancient Greek god.

"Perrrcy!" he bleated as he hurried to hide his hoof again. "What took you so long? That hydra should've taken about five minutes! Did you have trouble getting to the furnace in the school?"

Inwardly I groaned. Did everyone on the planet know about the furnace trick? Apparently I'd nodded off for a few minutes in Hydra 101 the other day.

"No, not at all," I lied smoothly. "I just had a little…trouble…after that." I hesitated for a minute, debating whether or not to mention the blond girl. Something told me I shouldn't go around telling the world, but Grover was my best friend. Plus I was going to go crazy if I didn't tell someone soon. "There was this girl…"

"A girl?" Grover made a strangled squeaking noise. "You almost gave me a heart attack because you were busy flirting?"

"No!" I said immediately. I could feel my cheeks heat up. "Not unless I really don't understand how flirting works."

Grover raised his eyebrows at me.

"Shut up," I grumbled. There wasn't exactly a ton of time to talk to girls when you were chasing monsters all over New York. I cleared my throat. "Anyway, she could see the hydra, and all she talked about was how much she wanted to kill me!"

"Hmm." Grover munched slowly on the rest of his can. "Beautiful? Deadly? Looked like a student?"

"Yes!" I was glad someone understood. "So you know who she was?"

"I know her kind," Grover said darkly. "Sounds like an empousa. It's usually easiest to make fun of their legs, since they're kind of self-conscious about them."

"Why?" I asked curiously. From the nice, long look I'd gotten at her legs, the girl had absolutely no reason to be self-conscious.

Grover stared at me. "Um, the whole one donkey leg, one bronze leg thing?"

I shook my head. "I think you've got it wrong, G-man. Definitely one hundred percent human. Take my word as a teenage guy."

Grover frowned. "You're sure?"

I nodded. "Positive. She looked just as normal as me or you. Well, me, anyway…" I glanced at the Coke can hanging from Grover's mouth.

"Well, some monsters are really good at disguising themselves," Grover offered, but it sounded pretty lame to me, like he was seriously reaching.

"She looked totally human," I insisted. "Usually monsters eventually reveal themselves, and she wouldn't have worried about getting picked up by the cops if she was a monster, would she?"

"Wait, what cops?" Grover asked suspiciously, which was the part of my question I'd really been hoping he wouldn't pick up on.

"Um…" I rubbed the back of my neck. "Well, see, there was this accident with a water heater…"

Grover sighed. "Percy! My confusion spell was only good for the bomb threat! How did you manage to draw police with a water heater?"

"Well, I kind of had to blow it up," I said sheepishly. "In the name of saving innocent lives, of course. It was heroic! Really!"

Grover raised his eyebrows at me, and I knew I was about to get a thirty-minute lecture on the importance of not ending every battle with an explosion. As he opened his mouth, I quickly stepped in. "Hey, look at the time. If we don't hurry, I'm going to be late for my training session with my dad!"

Grover glared at me, but he followed anyway. "He's not going to be happy you keep drawing attention to yourself, Percy. You remember the very first lesson he taught you, years ago…"

This time I didn't bother hiding my groan. Neither rain nor sleet nor snow nor threat of being blasted to bits by an impatient god could stop a satyr in lecture mode.

Thirty minutes of "I really learned my lesson this time!" and "of course I'll be more careful in the future!" later, Grover finally ran out of steam. Well, he stopped lecturing, at least. We were coming up on my apartment, so he might have just decided to wait until we were inside and my mom could take over for him. They were big on tag teaming like that.

Neither of us was expecting what we saw when we opened the door, though. My mom was there with her laptop, like always. And standing next to my mom was…my dad.

"Lord Poseidon," Grover said reverently, bowing low.

"Um, hey," I said awkwardly, trying not to slouch.

My dad looked amused for a second. "Hello, Percy. And Grover, my favorite satyr. I think perhaps I've mentioned this before, but the bowing is a bit unnecessary."

Grover opened his mouth as if to disagree, which meant I immediately slapped my hand over his face before he could say anything. My dad was pretty easygoing for an all-powerful god, but he wasn't fond of anyone disagreeing with him. It'd started more than a few feuds on Olympus. I still had to duck whenever an owl passed overhead thanks to his latest disagreement with Athena.

"So…I wasn't that late for training, was I?" It was a pretty lame attempt to lighten the mood, but I couldn't help it. It wasn't like my dad was in the neighborhood and decided to just drop by for a visit. We always did our training in his undersea palace, because he claimed he hated solid ground.

My father smiled faintly. "No, Percy, I only wish I were here to discuss your difficulty with the concept of punctuality. Or your highly inventive hydra battle strategy." His eyes twinkled, and I know I turned red. Would it be too much to ask for my dad to not see everything?

My mom frowned. "You were battling a hydra? In this weather, without a jacket?"

That's my mom. Want to fight a highly dangerous monster capable of killing you a million different ways? Have fun! Want to go outside in the middle of October without a jacket? You'd have better luck reasoning with the monster.

"Relax, Mom, it wasn't a big deal. There was plenty of superheated water to keep me warm." Before she could ask exactly what that meant, I turned back to my dad. "So why are you here then?"

He wasn't smiling anymore. "I'm afraid I…well, I'm not sure quite how to say this." He looked at my mom, but she just raised her eyebrows. Apparently my dad was on his own. "Look, Percy, I haven't been entirely honest with you. Do you remember back when you were seven, and you found out I wasn't human?"

I nodded. My mom had decided to go with a pool party for my birthday. The YMCA held the honor of being the first place to ever ban me.

"Do you remember what the first thing you said to me was?"

I thought back. "Uh, something like, 'Huh?' "

My dad's faint smile returned. "Well, yes, there was quite a bit of that. I knew my children weren't known for their brains, but I'd had slightly higher hopes for you."

"I was seven!" I protested, shooting a glare at Grover whose shoulders were shaking suspiciously.

"Some children are already traveling across the country fighting monsters by age seven, as certain goddesses never fail to remind me." Poseidon glared at the ceiling briefly, and my mom and I exchanged a look we usually reserved for conspiracy theorists on the subway. "Anyway," my dad said as he cleared his throat, "after you finally figured out what we were talking about, you turned to me and asked, 'So when do I get to meet Hercules?' "

I grimaced. I was seven. The only things I knew about Greek mythology came from the Disney movie, and Hercules was pretty awesome. Of course, it hadn't helped when my dad had introduced me to Grover a couple days later. I didn't bother to learn his name for two years. I just called him "Phil."

"Right," I said, remembering. "And you said I couldn't meet him, because Hercules had died a long time ago. Back when the gods still had a bunch of kids."

"Yes." My dad looked a little uncomfortable now, like he usually did whenever he had to do a parenting thing. And like he usually did when confronted with parenting, he turned to my mom.

She sighed. "Look, Percy, I haven't been home-schooling you so you could fight monsters full time. Or because I didn't think the schools could handle your dyslexia. The truth is…all demigods get home-schooled."

"Yeah, so?" I asked, not understanding what the big deal was.

My parents shared another look, and my mom repeated, "All demigods get home-schooled."

I was starting to get annoyed when suddenly her words sunk in. "Wait, so there were more demigods before me?"

My dad nodded. "Yes. And…well, not just before you."

I was confused, and it must have shown, because Grover spoke next. "Percy, you're not the only demigod alive today. There are actually quite a few."

My heart stopped, but only until I realized how angry I was. "So what was all that 'you have to fight monsters because no one else can' stuff? And the endless hours training by myself at the bottom of the ocean? And being told every day how 'special' I am, being the first demigod born in 150 years?"

"You are special," my mom said sharply. "And I'm not just saying that because I'm your mother. You're so special that we finally had to tell you all this. We were supposed to tell you months ago, but you were so happy…"

Now my mom looked like she was going to burst into tears, which made me feel guilty. I hadn't meant to make her cry, even if she'd been lying to me for almost ten years.

"Why now?" I asked instead, hoping to distract her. "Why today?"

My father glanced at the door. "The time has come for you to leave home, Percy. The extraction team should be here any moment."

"What?" I demanded, panicking. I looked at my mom. "I don't want to leave!"

Now my mom definitely had tears in her eyes. "We don't have a choice, Percy. If you stay here, we can't protect you anymore. And you'll be needed at camp."

" 'Protect me?' " I repeated in disbelief. I was the one who protected everyone else! Suddenly it dawned on me. "This is about the girl, isn't it?"

This stopped both my parents. Grover groaned.

"What girl?" asked my mom. She grinned a little. "Is she cute?"

I tried to stop it, but I know I blushed a little. Leave it to my mom to turn this into an opportunity to pry into my love life. I decided to ignore the question. "The blond girl who wants to kill me! Is she the reason I have to go into hiding?"

"No one said anything about hiding." My dad was probably trying to make me feel better, but given the monsters I'd faced lately, I wasn't sure hiding would be such a terrible thing. "Tell me about this girl."

Before I could, a knock came at the door, and my mom went to open it. I don't know what I was expecting. Mrs. Bayer from across the hall to borrow a cup of sugar, maybe. Old Mr. Norman telling us to keep the shouting down, even though everyone knew he was going deaf. Something like that.

I definitely was not expecting to see a man in a wheelchair surrounded by half a dozen kids in Greek armor. The man looked vaguely familiar, but not nearly as familiar as the gray-eyed blond girl behind him glaring directly at me.