PART I: THE POISON GARDEN

Annabeth could barely keep up, her little legs pumping as hard and fast as they could. Her lungs burned, her breath misting in the cold night air. The oversized leather jacket she wore weighed her down, but she couldn't stop to take it off.

Luke grabbed her hand and pulled her along, following Thalia and Grover down the dark country road in Long Island. Stars glittered above them, and the only sounds were their panting and the slap of shoes on asphalt.

"Almost there!" Grover called, his reedy voice echoing into the night.

Behind them, something screeched.

Annabeth ran faster. Thalia glanced backwards, her hand keeping its iron grip on her mace cannister.

"It's just over this hill- Argh!" Grover stumbled to the ground as a blur of black and red shot out of the shadows, narrowly missing him.

The hellhound didn't last long- Thalia's spear made short work of it -but it was enough.

A screech of laughter pierced the night, and goosebumps rose on the back of Annabeth's neck as a new sound emerged: that of scales rasping against pavement.

Thalia didn't wait to see what it was; in one lightning movement, she pulled Grover back to his feet and tugged him down the road, toward the hill that he had pointed out. Luke followed, scooping Annabeth up in a fireman's carry, ignoring her yelp of protest.

Thalia shoved Grover into the grass, and Annabeth struggled to see her face in the darkness, her own cheek pressed into Luke's bony shoulder.

Another laugh. A howl.

"We're not all going to make it," said Thalia. She still clutched her mace in one hand, and her short black hair, clumpy and damp with sweat, hung in her face. "You guys go on ahead, I'll keep them busy."

"No," Luke barked. "We're going to be fine." Annabeth could feel his chest rising and falling, rising and falling as his breathing grew rapid, not because of the long run, but because of Thalia.

"No," Thalia said calmly. "We're not." She glanced into the darkness of the road, cloaking whatever it was that hunted them, and Annabeth saw her eyes, wide and blue and beautiful. She tried to say something, but what came out of Annabeth's mouth was little more than an exhausted croak.

Thalia glanced back at her, and a small smile cut through the grim lines of her face. "Besides," she murmured, not to Annabeth, but to Luke. "You have to get Annabeth to safety. It's almost here."

"No-" Luke began, but the triumphant scream of the monster cut him off. Thalia whirled, her spear sprouting instantly out of the mace cannister, her shield springing up from her wrist.

And, at last, the monster came into view. A wicked, long green scaled tail, thick as an oak. Glowing green serpentine eyes. A crocodile grin. She had the torso and arms of a woman, though skeletal with gray-tinged skin, but the hindquarters of a huge snake.

Annabeth knew what she was. Another one of Zeus' scorned lovers.

The Lamia.

Annabeth knew Thalia recognized her too; her body stiffened, and her grip tightened on the spear, making it bristle with electricity. The monster slithered toward them, her speed belying the weight of her massive tail.

"Go!" she shouted as she dodged a swipe of the powerful green tail. The Lamia's smile grew wider, her teeth glinting in the dim light; she ignored Luke and Annabeth, glowing eyes fixed on the prize of Zeus' daughter. "Take them and run!"

Annabeth could feel Luke's hesitation; she wanted to get down and fight too, but she was so tired. Thalia dodged another swipe and lept into the air, her spear aimed for the monster's heart.

And Luke turned and ran, pulling the stunned Grover after him in one hand, and supporting Annabeth with the other. She shut her eyes against the sounds of battle.

She thought she might have heard Thalia, one last time, one last goodbye.

Then Luke cleared the hill and was stumbling down the other side, towards the farmhouse glowing in the distance.

When Annabeth woke two days later, in a soft cotton bed in the Big House, there was a towering pine on the top of the hill.

.

Percy pounded through the woods, Nico's skinny arms wrapped around his neck in a piggyback. He tried not to think about the Minotaur behind them, lumbering through the trees, creating a cacophony of broken branches and heavy, stomping hoofbeats. He had to get Nico, little six year old Nico di Angelo, to safety. He had promised Bianca.

Farm Road, Montauk. Percy had tried to stick close to the water, but he had lost his sense of direction in the woods. He didn't know where they were-

The Minotaur roared behind them, startling Percy out his panicked thoughts and into survival mode. Nico, from his piggyback position on his back, tightened his arms around Percy's neck.

The Minotaur was definitely gaining now. Percy did not know how long he had been running, but light filtered through the trees, gaining strength as dawn approached. The thing had crummy enough eyesight that it had a hard time tracking them, and, luckily (extremely luckily), there was little wind to spread their scent, but the increased light would not work in their favor.

The creek he followed seemed endless, winding between trees and boulders, never wide enough to be of real use. Nico was still clinging to his back, but Percy struggled to maintain his grip in his thighs. The kid was skinny enough that carrying him was never much of a challenge, but Percy had never supported him for so long at such a pace.

In the back of his mind, Percy marveled at how calm Nico was. Percy could feel his eyelashes tickling the back of his neck, where Nico's eyes were shut tight against the grave reality of their situation. He also wondered how the hell they were still alive.

Percy focused on his breathing, in and out, in and out, but not too loudly, to avoid giving the very persistent Minotaur another means of tracking him. The forest had a layer of pinestraw to help mask his footfalls, but he could not avoid the twigs and pinecones blocking his path, stomping over them with loud snaps and crunches. He ducked to avoid a low hanging branch and-

Hope surged through him.

The beach, at last.

The creek was widening, the water rushing faster as it raced toward the sea, the tree roots becoming more sparse. Percy leapt into the stream, his shoes splashing through it, sliding over rocks and the plants that thrived in the brackish water. The Minotaur bellowed behind them, but Percy didn't care.

We're going to make it. It's going to be-

Nico screamed. A loud, piercing yelp that startled Percy so much that Nico's legs slipped from his grip, and he went tumbling into the creek.

"No! Percy, we can't-" Nico was sobbing, tears running down his face, and Percy tried to scoop him up, to pull him toward the ocean, but Nico struggled away from him, squirming toward the monster that was about to kill them. His pale cheeks had turned an ugly, tear streaked red, and the water rushed past him, soaking his dirty clothes.

"Nico! We don't have time for this! We have to go!" Percy had the fleeting thought that he would regret such harsh words later, but they had to move. NOW. The monster was gaining, the distance closing every second, there would probably be more- Nico shook his head, trying to get to his feet, his barefeet slipping on the creek bed as he avoided Percy's attempts to grab him. His high pitched voice was shaking. "No! Something awful's going to-to-"

The Minotaur roared, and Percy suddenly realized that it was right fucking there. It had finally gotten close enough to charge, head down, horns sharpened to a deadly point, its footfalls shaking the earth beneath them.

Sally Jackson's voice floated through Percy's mind. Wait as it charges, then jump out of the way. The Minotaur is not smart. Confuse it.

Percy waited, staring at the snot tripping from the thing's snout, the underwear it wore truly disgusting-

He dove, tackling Nico out of the way as the Minotaur blasted past, a wave of reeking air hitting them as it blundered into the woods.

Before Nico could resist anymore, Percy snatched him up, hauling him over his shoulder as he sloshed through the creek, toward the beach and away from those gods-damned woods. The water felt rejuvenating on Percy's skin.

NIco, stunned for only a moment, began to struggle, screaming as they neared the sand. He did not seem to care about the giant monster currently trying to kill them, only about keeping Percy away from the beach.

The noise rioted against Percy's eardrums as he struggled to listen for the thundering steps of the monster. The water sloshed around his shins. The waves pounding the shore ahead seemed to beckon to him. Percy followed their call, powerless to do anything other than slog toward the safety of his father's domain. He could feel his heart pounding in his chest, exhausted. Nico continued to struggle.

Percy was so tired.

Then Nico stopped screaming, his voice calling out a warning as Percy suddenly became aware of the Minotaur's stomping charge. Percy whirled around, turning to face it, to apply the tactics his mother had taught him- but its arms were out, ready to snatch them out of the water, to drag them back into its Labyrinth. And devour, as it had done all those centuries ago.

Percy had to protect Nico. He had promised Bianca.

He dumped the kid, racing forward as the Minotaur hit the water, and threw himself toward it, his right hand already summoning Riptide, the tiny pen growing into the ancient Celestial Bronze sword.

As if in slow motion, Percy watched the sword, felt himself flying through the air- he had jumped possibly high, he realized, the water had propelled him forward, forward, forward-

Percy landed on the horn of the Minotaur, the point, sharp from years of killing, slamming through his gut- his spine exploded in pain-

Riptide plunged into the monster's eye-

Percy fell back into the water in an explosion of golden dust.

.

Sixteen year old Piper McLean watched as Annabeth Chase poked at the ancient VCR in the small living room of the Big House.

"'Kay, so," she was saying, "Here's the orientation film, and after that I'll take you on the tour. Sound okay?"

Piper could only nod. The day had been a blur of impossible creatures and revelations- her mother, a goddess.

She twisted the small decorative pillow in her lap, the fabric clearly old and worn, but comforting. Piper looked down at the beige material, her gaze sliding from the pillow to her soulmark, the name "Jason Grace" printed clearly on her left ring finger.

She wondered if he was here.

On the floor in front of the box-like television, Annabeth made a small sound of triumph. "Ah! Here we go."

The screen flickered to life, and Piper forgot her soulmark as the film - clearly ancient and outdated - explained this new world Piper had been thrown into when a renegade wind spirit attacked her and her friends on a field trip to the Grand Canyon. Gods and goddesses, Western Civilization. Parentage. Monsters. Something called the Mist. Even soulmarks, common among mortals, were rooted in the divine.

Oh, God (or gods?). Where was Leo when she needed him?

When the movie ended, Annabeth led the way outside. A self-proclaimed daughter of Athena, she looked tired, but Piper had a feeling that she usually looked like that. Her eyes were slightly sad, though she was quick to smile.

Piper followed Annabeth down the porch steps and across the grass towards a cluster of cabins. "Okay, so," Annabeth was saying, "Since we don't know who your mom is, you'll stay in the Hermes cabin. Hermes is the god of travellers, so they take in the undetermined kids."

Piper could only nod as they neared Cabin 11, where a pair of twins sat on the stoop. They glanced up from the notepad they were scribbling on and hastily flipped it over.

"Hermes is also the god of thieves," Annabeth muttered. "So watch your wallet."

Oh, well. With all the crap Piper had stolen over the years, she'd probably fit right in. Too bad it was her mom that was the goddess.

"Is Leo going to stay here too?"

Annabeth shook her head. "No. The flaming hammer thing? That means his dad is Hephaestus, the god of fire and blacksmiths. But he will be in Cabin 9, which is just next door."

"Why didn't you show him the orientation video?"

"If we know someone's parentage, we like to have their siblings explain it. He's probably in the forge right now."

"You guys have a forge?"

Annabeth ignored her as they reached the twins. "Guys, this is Piper McLean, undetermined for now. Piper, this is Connor and Travis Stoll, the heads of the Hermes cabin."

They nodded in unison, muttering greetings as one shuffled with the notepad. Annabeth frowned at it, and was opening her mouth to comment, when the door behind them swung open and a pale boy in a retro-looking aviator jacket stumbled out, blinking rapidly in the bright sunlight. He glanced down at the Stoll brothers before focusing on Annabeth, ignoring Piper completely; Piper wouldn't have thought it possible, but his face went even whiter.

Annabeth smiled slightly at him before turning to Piper. "This is Nico di Angelo. He's been here almost as long as I have. Nico, this is Piper."

Nico tore his eyes away from Annabeth to nod at Piper before moving past the Stolls and speeding away from them, all but running in his haste to get away from them.

Annabeth sighed. "Well, anyway. Come on, Piper, I'll show you the climbing wall."

As they walked past a small building that Annabeth said was the bathrooms, Piper asked, "What was that guy's deal?"

Annabeth frowned. "It's a long story."

"Try me."

Sighing, Annabeth paused as they neared a small lake, where canoes floated in the water. "A lot of major mortal wars are fueled by the gods. World War Two was a rift between the children of Zeus and Poseidon on one side, and Hades' kids on the other. It was. . . not good. So after the war, they - we call them the Big Three - they swore an oath to not to have anymore kids with mortals. And Nico is a son of Hades."

"So he's the only kid of the Big Three, and he's not even supposed to exist." Piper couldn't imagine how that must feel, even if that didn't explain how Nico had fixated on Annabeth at the cabin. She leaned over to gaze into the clear blue water, and was startled to see eyes blinking back up at her. Women, their dark hair drifting in the water, smiled from where they sat at the bottom of the crystal clear lake, their teeth a little too sharp. Annabeth leaned over too, and nodded down at them. "Naiads. Harmless, but a little too flirtatious."

Maybe Nico just had a crush, Piper thought. Annabeth was stunning, with her curly blond hair and grey eyes flashing in the light reflected off the water.

"And, no, there have been other children," Annabeth continued. "Nico had a sister, and there was a son of Poseidon, and a daughter of Zeus."

"What happened to them?"

"Dead. When one is found out, the other gods send out monsters to hunt them. Nico's the only one that made it the Camp Half-Blood alive."

Piper felt her blood run cold. "So. . . the other gods basically killed them."

Annabeth shrugged. "It's more complicated than that. The gods have been around or so long, and they're so intermarried and have betrayed each other so many times. None of it- none of this life is easy." She looked up at Piper, her attempt at a smile turning more into a grimace. "If you hadn't been attacked, we try to keep most demigods in the dark about their parentage. Once you know about it, the easier you attract monsters."

Nodding, Piper swallowed thickly. It felt like there was a tennis ball in her throat. "I- it feels like my already complicated life just got a whole lot more complex."

Annabeth patted Piper's arm. "Come on, I'll show you the armory. Playing with knives always cheers me up."

.

Leo Valdez liked Camp Half-Blood. It explained, well, a lot about his life.

Most of it, anyway.

He wasn't really sure about his fire powers, even if they came in handy in the forge, where Beckendorf taught him how to make swords and shields- it wasn't even that hard. He'd even made Piper a new sheath for her dagger, Katoptris, one that was pretty enough to satisfy even Piper's new Aphrodite siblings, but still simple enough to suit Piper.

It had been a Thing, Piper's claiming. At the campfire and sing-a-long at the end of their first day, Piper had suddenly exploded into an insanely good looking person that barely even looked like the Piper Leo knew; she had complained for days about its effects, purposely wearing ratty clothes until the charm wore off.

He'd tried to flirt with her cabin leader, Silena, but she seemed a lot more interested in Beckendorf, so he'd quickly given up. The rest of the Aphrodite kids had looked at him like A) he was garbage, or B) they would eat him for lunch.

Normally Leo would totally be down for being someone's lunch, as he didn't have a soulmark and probably never would, but Piper had warned him away, going so far as to threaten to charmspeak him away from them. Piper had lots of feelings about the charmspeak, most of all guilt over taking away someone's free will, so Leo knew she was serious.

Unlike Piper, Leo liked his siblings, especially Beckendorf, who sometimes even chuckled at Leo's terrible jokes, and was teaching him all about the forge and the workings of Cabin 9, which had a lot going on that not even Chiron knew about. He liked the Stoll brothers, and had helped them play a few practical jokes on the other cabins. He liked sitting in the sun by the canoe lake, flirting with the girls who came by and rolled their eyes at him. He liked the lessons Annabeth gave him and Piper on swordplay and how to kill monsters and Ancient Greek.

Leo just liked Camp Half-Blood. It was a million times better than any of his foster homes, or the Wilderness School, even if it had that same free-for-all vibe.

It even began to feel like home.

So the bulls came as a surprise.

Leo woke one morning a few weeks after entering camp to the clangor of alarm bells and the much closer shriek of Cabin 9's security system. Stumbling out of bed, he almost ran into Nyssa, who was buckling a chest plate over her PJs.

"What-"

"The Camp's under attack!" she called over her shoulder as she snatched up a hammer as long as her arm and slammed the button to open the vault doors to the cabin; the gears whined as they spun faster than Leo had ever seen them, and the doors shot open. Nyssa darted between them, hammer poised for the attack.

Leo began to chase after her, but then went back for pants.

When he got outside, Leo's first impression was of a rodeo gone horribly, horribly wrong. Campers in various stages of dress (some with armor, some without) tried to corral a pair of ginormous bulls away from the cabins. The things glowed in the early morning sun, and Leo was confused to see the grass beneath their massive hooves catch fire.

"Colchis bulls," said a voice beside him, and Leo looked around to see Annabeth, dressed in a NYU t-shirt and sleep shorts, hair in a sleep-matted braid; her knife was clutched in one hand. "Made by Hephaestus. Only way to touch them without burning to a crisp is Medea's SPF 50,000."

Leo winced as a camper got close enough to a bull's rear end that it kicked, and the camper had to duck to avoid getting a hoof to the face. "Got a bottle?"

Stupid question. Even now, her dagger was sheathed, and Annabeth was glopping sunscreen on her hands and arms and legs. Tossing Leo the empty bottle ("Tropical Coconut Scented!" enthused the label), she pulled out her dagger and charged into the fray.

Shit. Tough lady.

In the fight, Leo could see Nyssa in front of a bull, swinging her hammer in an arc that barely dented its chest; she dove out of the way to escape a plume of red hot fire from its horns.

Fire.

Leo realized he had to do something heroic, not just stand around and watch as some bulls flambéed his friends. Ducking back into Cabin 9, he grabbed the first thing he could reach off the weapons wall, and ran back outside and straight toward the nearest bull.

It was only when Leo got within ten feet of the thing that he realized he had grabbed the weed whacker.

Oh well. It would have to do. It was a godly weed whacker, after all. Leo tugged the power cord, and it roared to life. He dove between two campers and found himself looking into the ruby eyes of the bull.

Fuck, that's scary.

It bellowed, fire spitting from it horns, and Leo could hear the other campers yelling as he swung the weed wacker toward the horn and fire washed over him, scorching the grass.

It was like a warm bath. The fire didn't even singe his clothes.

The weed wacker sliced through one horn and then the other, and Leo could feel himself grinning as he swung the whacker again, slicing through the copper skin and revealing the intricate wiring beneath. Leo speared the whacker into the bull's chest, plunging it into the gears with all his strength.

And, miracle of miracles, the huge bronze body of the bull shuddered, the light fading from the rubies, and keeled over.

Leo powered off the weed whacker, not bothering to pull it out of the bull's massive torso. The other bull was in the process of being killed- he could see Annabeth on the bull's back and holding on for dear life as an Ares girl slashed with her spear, her siblings clustered around it, forming an impenetrable wall of shields and pure muscle.

He looked around to see Nyssa and the others gaping at him, their pajamas singed from the fight. "But-" she spluttered, "The fire!"

Leo wanted to say something cool or at least not completely stupid, but all he could manage was "Uhhh. . ." It dawned on him that the whole thing had lasted about a minute; it had felt so much longer when he had been eye to eye with the bull.

The Ares girl - he remembered now that her name was Clarisse - yelled in triumph as the second bull went down, Annabeth throwing herself clear to avoid being crushed.

She tumbled to a stop close by and was on her feet in a flash; Leo braced himself, ready to be yelled at, but she was looking in horror at the nearby Silena and Piper. "How did they get past the border line!" she demanded, and, not waiting for an answer, took off toward the Big House.

Piper and Silena ran after her, Clarisse in hot pursuit, and Leo exchanged one look with Nyssa before they both sprinted after them. Over his own panting, Leo could hear other campers racing behind them as they all followed Annabeth over the central creek and past the Arts and Crafts cabin, pounding up Half Blood Hill toward the towering pine tree that marked the camp boundary.

As one, the campers skidded to a stop. Leo could hear gasps and murmurs of shock at the site of the pine tree.

Someone had bored a hole in the trunk, and it oozed green sap. The pine needles were already tinged yellow; Leo could almost see the sickness passing through the tree.

Chiron was already bent beside it, examining the hole with a grimace. Annabeth watched, her face pale, as he shook his head. "Poisoned."

Leo exchanged a puzzled glance with Piper. What was the big deal about a dying tree? It was a bummer, but-

Beside Chiron, shadows rippled, and Nico di Angelo stumbled into the light; like Annabeth, he looked desolate. "Percy's too. The roots have been poisoned, the whole thing looks sick."

Another murmur went through the campers, and Chiron at looked up at them. He stood up, his front legs unfolding beneath him. "Campers," he said, his voice carrying with ease. "Please go enjoy breakfast in the mess hall; we will do her no good just staring. Counselors, there will be a war council at noon, the usual place."

Muttering, the campers dispersed. Leo stayed where he was beside Piper, who was looking at Annabeth with concern. Nico put his hand to the bark of the tree and winced. "Dying. She's got a few weeks, maybe a little over a month."

"And Perseus?" Chiron asked calmly.

Nico shrugged, but his bottom lip trembled. "Longer, probably. The water will do its best for him. But it won't hold off forever." He glanced at Annabeth, who was still staring at the hole in the tree, hand clutched to her camp necklace, before continuing. "You can't heal it."

It wasn't a question.

Chiron shook his head anyway. "I will try my bes-"

"It was Luke."

Annabeth had let go of her necklace; now she clutched her dagger. "It was Luke," she repeated. "He did this. He tried to destroy Olympus and now- now, he's trying to destroy Camp Half-Blood too."

.

Nico de Angelo sat on the grass next to the small delta created by the creek flowing into the ocean. It was a nice spot, usually quiet and peaceful, with the woods at his back and the ocean before him.

But that wasn't why Nico came here.

Nico came here because this was Percy Jackson's final resting place.

The water lilies that had replaced Percy's body spread through the delta, created a miniature ecosystem, a safe haven for fish and small sea creatures. When Percy had died nine years ago, there had been only one stem in the center of the delta with one small flower, but it had grown so the flowers spread from the creek to a few feet into the sea, rising and falling in the current. Nico had looked through a book on water plants; Percy's leaves and flowers were unlike anything he could find, as if Poseidon had created a new species just for his son. It flowered year-round, and thrived in the brackish water. The blooms were a myriad of colors, from a bright red to a musty purple to a brilliant blue, the most common color.

But like Thalia's needles, the brilliant green leaves had dulled into a sickly yellow, and the blossoms were wilting. A few small fish floated in the water, dead. Nico could see a trail of carnage, as if someone had stomped through them to get to the central stem, over turning as much as they could and ripping up roots and flowers. The central stem now had a series of gouges in it; the poisoner had to be more careful here than with Thalia. They couldn't have just ripped the stem out; that way, it could be replanted by the nereids that sometimes visited the site to check up on the sea god's son.

Already, Nico could see one, her dark hair swaying down her back as she examined a blossom. As usual, she ignored him, as all the nereids ignored the few campers that happened upon them. Since Nico had taken to haunting the spot when he arrived at Camp Half-Blood, other campers tended to avoid it, including Annabeth, unless she was in a particularly awful mood and didn't want to be found.

After Percy's death, Nico had felt terrible; he knew it was his fault that Percy had not survived. Nico had screamed. He had tried to get Percy to stop. After they figured out his parentage, Chiron had told him that he had probably had a premonition of Percy's death and tried to stop it, but Nico couldn't remember much. It was all a blur of trees and darkness and the Minotaur and Percy trying to get him to stop crying so they could go.

And to find out years later from Luke that Percy had a soulmate, a beautiful, smart girl with Percy's name written somewhere on her body. . . guilt ate Nico alive. Because Percy should have gotten to meet her. Percy should have lived long enough to get to know Annabeth, whom Nico had deprived of a soulmate.

The nereid in the water sighed softly and sunk down to disappear beneath the dying leaves.