A/N: Yes, I'm back! This fic was written for the PJOHOO Big Bang on tumblr (and has been posted there and on Ao3), but I'm excited to share with you guys here this 'extended scenes' version with more content! It's a different style from my DoW series, but I hope you'll enjoy it anyway! If anything, it's something to read while I work on the next DoW instalment; with any luck, by the time I finish posting this, I will be ready with that!

I'd like to thank my betas on this piece, supernaturally-percyjackson and preciouschildrenofolympus, for their incredible commitment to such a long fic and the amazing job they did helping me polish it up (and still sticking with me for the extras that I'll be including in this version). preciouschildrenofolympus has also drawn art for the fic, which I will point out in the relevant chapters!

Summary: Percy and Annabeth intended to retire and spend a quiet four years at college in New Rome. However, old enemies have other ideas, and one very determined attack leaves Percy poisoned and fighting for his life and Annabeth facing the difficult decision of giving him the only cure: water from the Lethe...and dealing with the heartbreaking side-effects. There is hope, though, but will Percy, Annabeth, and their friends have the courage to brave Tartarus again to retrieve Percy's memories from the edge of Chaos?

Note: This story is rated R (or M, if that's your system) for adult themes. Although no explicit material is covered, there is reference to some dark stuff in later chapters. Appropriate warnings will be given before each chapter.

OoOoOoOoOoO

If somebody had been waiting for Percy when he first woke up, if they'd convinced Percy that his name was Bob and he was a friend of the Titans and the giants...would Percy have believed it? Would he have felt betrayed once he found out his true identity?

—The House of Hades, chpt 62

OoOoOoOoOoO

I

ANNABETH

When Percy first proposed the idea of living in New Rome to Annabeth, she had vehemently opposed it. However, after a year of college there, the place had definitely grown on her.

Inside the Pomerian Line was a cosy world of demigods living tucked away from the constant danger of monster attacks and vengeful deities. The university's architectural design programme was first-rate, as was to be expected in a city that was modelled after the original Greek and Roman ones. Her friends were often around: Reyna lived nearby, having recently retired from the legion and passed on her praetorship to Hazel. The latter Annabeth saw often as well, along with Frank, since they attended senate meetings regularly. Camp Half-Blood had finally established a regular exchange programme with Camp Jupiter, spearheaded by Jason and Piper, with a cross-country transportation service courtesy of Leo and Festus. Annabeth's half-brother Malcolm had been in the first wave of exchange heroes. She even got out into San Francisco occasionally to visit her dad, and while she missed Chiron dearly, there were always Iris messages and summers back on Long Island.

With all these perks, Annabeth had thought she'd be more than grateful for the peaceful, quiet life that New Rome offered. And she was—except she found herself getting restless sometimes. Maybe it was because as a demigod, fighting was in her blood.

After she and Percy got back from a summer visit to New York, where Chiron had joked about them getting rusty in their training, they began to crave action. They got into the chariot races at the Circus Maximus, which brought back fond memories of the first time they'd ever raced a chariot at Camp Half-Blood. They joined the weekly war games with the Twelfth Legion in the Field of Mars, to the delight of the Fifth Cohort.

And then they started venturing out into the world.

It became a weekly ritual. They would jog down the cobbled paths of New Rome, over the Via Praetoria and through the barracks. Once across the Little Tiber, it was a short sprint into Berkeley, where they would make straight for the coast. Percy would dive into the bay and keep pace with Annabeth as she loped down Eastshore State Park. It was a good ten-miler to start the day, and although New Rome was peppered with top-notch cafés, Annabeth became quite fond of finishing her run at Philz Coffee on Ninth Street before strolling back hand-in-hand with Percy into New Rome for classes.

At first the Camp Jupiter sentries at the Caldecott Tunnel were aghast at their leaving the safety of the camp boundaries in such a blasé fashion, but after a few weeks of it, they got accustomed to seeing the two of them jog by in the morning and return without issue some time later.

Sure, they ran into the occasional monster—sea serpents, giant carnivorous seagulls, turtles with mouths full of sharp teeth—but after two wars and a trek through Tartarus, the odd monster that surfaced was no more than a minor irritation, easily dispatched before they continued their respective jog and swim. Annabeth grew to think of them more as disturbances that got in the way of her coffee time at Philz.

So when the crazy woman on a horse showed up, Annabeth barely batted an eyelid.

Unfortunately, she was about to pay for her hubris.

At first, Annabeth thought the steed that burst forth from the bay was a Hippocampus. As its lower half broke the surface in a ferocious leap, she glimpsed a fish tail and flippers where a horse would have legs. But then it landed on the concrete of Berkeley Pier with the definite solid thump of hooves. It stood before her, a slavering monster horse with sharp, glistening teeth and evil, glowing eyes. Its long, dark mane flowed fluidly down its coal-black coat.

On its back rode a muscular woman with hair the colour of algae. She seemed to be wearing a skin-tight outfit covered with loud prints, but then Annabeth realised that the only stitch of clothing on her were her green tights. Every inch of her bare upper body was inked with tattoos: a garish collection of multi-coloured designs with no real pattern to them. Symbols and shapes and pictures of underwater plants and creatures swirled together. Most prominent of the lot was an enormous heart splashed across her chest, with the words JB + H 4-EVA inside. Annabeth had no idea what it was supposed to mean.

The tattooed woman's hands pulled sharply on the reins of her horse, which were the same fluid material as the creature's mane and led to the bridle that went through its mouth. The demon horse's nostrils flared as its rider held it steady.

Something about the combination struck Annabeth as odd. She'd never seen anything like this horse before, and the way it had seemed to have flippers and a tail when it first burst from the water…

'At last,' said Tattoo-woman, glaring at Annabeth. 'I have found you. And now you shall die.'

She spoke as though she knew Annabeth, but Annabeth was at a loss as to when she might have encountered this horseback version of a Hell's Angel before.

'I think you might have the wrong person,' she said, but she slipped the bracelet she always wore off her wrist. It had a number of charms on it and one of them, a wishbone, disguised her personal weapon. 'I don't think we've met.'

'Oh, we have not,' agreed Tattoo-woman. 'I don't expect you to recognise me. We Nereids never do get any attention. But I am Hipponoe, and you, Annabeth Chase, killed my lover.'

It was possible. Annabeth had killed plenty of monsters, though she wouldn't have imagined a Nereid to be dating one. She knew nothing of Hipponoe, except that the ancient Greek translated loosely into 'Temper of Horses'—pretty apt, given how she was currently spurring a bad-tempered horse to attack. The heart on her chest might be a clue, but Annabeth couldn't remember killing any monster with the initials 'J.B.' either.

Not that it really mattered. Whatever her reasons, Hipponoe was clearly out for vengeance, and that meant a fight. Annabeth rubbed her finger and thumb over the central curve of her wishbone charm. It elongated into the drakon-bone sword that she had acquired from the giant Damasen in Tartarus two years ago.

Before she could charge Hipponoe and her horse, though, a jet of water came blasting out of the bay and crashed into the Nereid. It nearly unseated her, but she kept a tight hold on the reins of her horse. A flash of bronze followed, a blade that would have stabbed into Hipponoe, except her steed moved out of the way with lightning-quick speed.

Percy landed on the pier next to Annabeth, his own sword, Riptide, in his hands. Though he'd been swimming, his black hair and college t-shirt were completely dry—just one of his many magical talents as a son of the sea god.

Percy's green eyes flashed with concern for Annabeth. 'You all right?'

'I had it under control,' Annabeth huffed, pushing a few stray curls that had escaped from her ponytail out of her face. Then her eyes widened and she shoved Percy aside. 'Look out!'

Hipponoe had regained control of her horse, but instead of charging, as Annabeth would have expected, the horse opened its mouth and spewed a mouthful of fire at them.

Percy shoved a column of water at the flames. 'You've gotta be kidding me,' he said. 'How can a water creature breathe fire?'

Something tugged at Annabeth's memory. 'It's not Greek,' she said. 'I mean, Hipponoe is, but I think her horse is…'

Before she could place which myth it was, Hipponoe and her horse came back for a second round.

'Great,' Percy grumbled. 'Do all the different legends have to come after us? I mean, first there were the Romans, and then the Egyptian stuff, and then that craziness with your cousin that I still don't understand. Now what?'

He fended off another fiery blast from the horse, sending up a wall of smoke as his water jets extinguished the fire.

Hipponoe let out a frustrated cry. 'You are in my way, son of Poseidon! Leave! I have no quarrel with you. It is this accursed murderess I have come to destroy!'

'You know, I've really got no clue what you're talking about,' Annabeth said. She swung her sword and it hit razor-sharp horse teeth with a metallic clang. The horse tried to clamp its teeth over the blade, but to Annabeth's confusion, Hipponoe yanked it back sharply.

The horse looked disappointed. It was almost as though it wanted the blade to slice into its mouth.

'Do not deny it, daughter of Athena,' Hipponoe said. 'I have spent years tracing the death of Joe Bob. I divined it with certainty: it was you who stabbed him in the back!'

'Joe Bob?' Percy's eyes widened. 'Oh man, you're Babycakes?'

Annabeth had no idea what he was talking about.

'That was his name for me!' Hipponoe howled.

'The Canadian giants,' Percy said. 'Laistry-whatever-you-call-them. Back when I was at Meriwether Prep.'

A dim memory of flaming dodgeballs and explosions in a school gym crept into Annabeth's mind. 'I can't believe you still remember that,' she marvelled.

'Enough talk!' Hipponoe snarled. She yanked the reins, pulling tightly on the horse's bit, and suddenly it shifted its shape, becoming a hulking beast that seemed like a hurricane full of gnashing teeth. 'Perhaps you like my kelpie better in this form. Yes, I think this is better. I will have you ripped to shreds!'

'What is that thing?' Percy demanded.

At the word 'kelpie', Annabeth's brain finally made the connection. This creature wasn't Greek. And while her knowledge of myths beyond the Greek and Roman pantheon wasn't extensive, she'd investigated this one when she'd been helping her cousin Magnus. The kelpie…a fire-breathing, shape-shifting water horse.

Well, that seemed about right.

'I think it's from Scotland,' Annabeth said.

'Who cares where it's from!' Percy dragged her out of the way as the kelpie tore up the pier in front of them. 'How do we kill it?'

'I—I'm not sure! But we can't let it destroy Berkeley!'

'Right.' Percy grabbed her by the waist and leapt off the pier. Annabeth yelped as they hit the cold waters of San Francisco Bay.

Hipponoe and the hurricane-kelpie turned and tried to follow them in the water, but the gnashing whirlwind of teeth couldn't do any more than churn up violent waves on the water's surface. Percy made the waves rise up to pummel Hipponoe. Unfortunately, after the shock of the first attack, the Nereid gained control and the water splashed harmlessly back down into the bay.

'Fool! I come from the sea, son of Poseidon. You cannot fight me with water.' Her grip tightened on her reins. It was hard to tell in the black hurricane, but the lines seemed to cut a groove into it near the top. The whirling dissolved and the kelpie reformed in the shape of a Hippocampus with the original black coat and mane of its upper body. The kelpie tossed its head, straining against the sinuous bridle and the bit that ran through its mouth.

'The bridle!' Annabeth's eyes widened. 'Percy, we can't kill it, but whoever holds the bridle controls it.' If they could just unseat Hipponoe… 'Give me a boost!'

Percy understood immediately. The water that was churning beneath her seemed to solidify. Annabeth kicked hard against it and Percy gave her another little push into the air. She leapt and soared through the air as Hipponoe and the kelpie bore down on them. Her feet slammed into Hipponoe from behind, knocking the Nereid sideways. Annabeth sliced downwards with her sword and cut the reins away from Hipponoe's hands.

With a howl of outrage, Hipponoe tumbled from the kelpie's back into the water. Percy immediately swam up and held Riptide to her throat.

Freed from Hipponoe's control, the kelpie went wild. Annabeth's heart leapt into her mouth as it plunged into the water with a thunderous noise, taking her with it. She remembered another snatch of the paragraph she'd read about kelpies: they drown humans by submerging with them into deep waters.

Oh no, you don't, Annabeth thought firmly. She could see the reins flowing back from the kelpie's head, not quite tangled yet. She reached for them and felt her hands close over the sinewy strands. The kelpie jerked, halted in its downward dive. It bucked beneath Annabeth, struggling against her, but she grappled for control. Finally, when her lungs were just about ready to burst, the kelpie's body slacked as though resigned.

Annabeth tugged on the reins and they rose, charging up to the surface. The kelpie burst out of the water and landed back on Berkeley Pier—what was left of it, anyway—its lower half shifting from fish back to horse.

'I'm okay!' Annabeth yelled, out of breath. 'I got the kelpie!'

Percy and Hipponoe bobbed in the bay twenty feet away. He swam her over at sword point and yanked her up onto the pier.

'Look,' he said, 'we don't want to kill you. But you can't come threatening my girlfriend, okay? We're sorry about Joe Bob, but he did try to kill me, you know.'

Hipponoe glared at him. 'No excuses, son of Poseidon.' She extracted a vial from a hidden pocket in her tights. It glowed with green light, like Greek fire. 'One way or another, the girl must die!'

She flung the vial towards Annabeth and the kelpie.

Percy intercepted it with a swipe of Riptide. 'Over my dead body,' he told Hipponoe.

The vial exploded.

Annabeth screamed, but it wasn't Greek fire. A splash of electric-green liquid washed over Percy. Hipponoe rolled out of the way.

'You fool!' she screeched.

For a moment, Percy just stood there, covered with what looked like bright green slime. Then he collapsed on the ground, flopping like a fish.

Annabeth screamed again.

'What did you do to him?'

Hipponoe's look of outrage gave way to laughter. She pushed herself to her feet and smirked at Annabeth.

'Poison,' she said smugly. 'I spent a long time preparing for our meeting, you know. I planned for every contingency. I sourced the most insidious venom, the strongest toxins, to create this. There is no earthly cure. It was meant for you, Annabeth Chase. But perhaps this is a more fitting punishment after all. You will suffer as I did, with the pain of losing the one you loved.'

Percy stopped convulsing and lay perfectly still on the concrete. A frost of fear spread icy tendrils through Annabeth's veins.

'No!' Without thinking, she spurred the kelpie forward and nudged Percy off the pier, into the water. She prayed it would work—as the son of Poseidon, water rejuvenated Percy, sometimes better than nectar and ambrosia. At any rate, it was the only thing she had on hand to try. If anything, it should at least slow or dull the effects of Hipponoe's poison, buying him time until she could get help.

And then she turned to Hipponoe. The Nereid seemed resigned to defeat now. Even as Annabeth bore down on her, she smiled in satisfaction.

'Even better, Annabeth Chase. You have hastened your boyfriend's demise. The water will only help the poison spread faster. And I—I will find my Joe Bob now.'

She crumbled into dust beneath the kelpie's hooves.

'No,' Annabeth repeated frantically, hoping that Hipponoe had been lying. At her command, the kelpie dove into the water.

She found Percy easily—there was an unearthly glow around his head that seemed to intensify with every passing second. Annabeth hauled his limp body onto the back of the kelpie and they surfaced together.

'Percy,' she whispered. 'Oh gods, why?' He'd gotten in the way of poison meant for her, and she'd gone and made it worse by shoving him into the water.

But she couldn't collapse in despair now. Percy's breathing was rapid and shallow and his pulse was faint, but he was still hanging on to life. She had to get him back to Camp Jupiter, find a medic…there had to be a way to save him. She wasn't going to let a stupid, bitter Nereid take him from her.

Annabeth wrapped her arms around Percy and tightened her grip on the kelpie's reins.

'Camp Jupiter,' she told it. 'Hurry.'

OoOoO

The guards on duty at the Caldecott Tunnel door just about had a heart attack when Annabeth charged up on a black demon horse with an evil glare.

Or, more accurately, her friend Will did. The other guard, Clovis, was snoozing on duty, and didn't notice until the kelpie snorted in his face and he awoke with a yelp, his droopy, calf-like eyes uncharacteristically wide. Then he nearly had a coronary.

Both boys were on their exchange year from Camp Half-Blood, and Annabeth was glad to see them. Percy definitely needed the gift of healing that Will, the sunny-haired son of Apollo, had inherited. And Clovis might spend most of his time sleeping, but when he did wake up, the son of Hypnos had some pretty useful powers as well.

'Where in Hades did you get that beast?' Will said. 'Uh—it's not actually from the Underworld, is it?'

'No,' said another voice. Lounging by the tunnel entrance was another demigod Annabeth hadn't noticed at first, probably because Nico di Angelo tended to blend neatly into the shadows around him. He also hadn't jumped ten feet into the air upon seeing the kelpie.

'What's wrong with Percy?' he asked.

'Poison,' Annabeth said, fighting to keep her voice steady. 'Will, can you—'

'Yeah. Um, what are you going to do about the horse—?'

In its current form, the kelpie wouldn't fit through the tunnel door, but somehow Annabeth knew what to do. She jerked twice on its reins and it morphed into a pug with the same evil eyes. The bridle turned into a collar that still extended into its mouth. Annabeth handed the dog to Nico and placed his free hand firmly on the collar.

'Take that to Hazel,' she said, figuring that Nico's sister, a daughter of the Underworld with a fondness for fierce, fast horses, would probably know best what to do with the kelpie. 'Don't let go of the bridle—er, collar.'

While Nico took the pug-kelpie off to Hazel, Will and Clovis lifted Percy between them. Together, they made their way to the infirmary in the legion barracks.

Annabeth clenched her fists as she watched Will assess Percy. At the age of ten, Will had already been Camp Half-Blood's best healer; in the eight years since, his healing magic had grown much more powerful. So when Will's face went pale after he put his hands over Percy, feeling for the damage, Annabeth's heart sank.

'It's his head,' Will said. 'His body's actually fine, but his brain—there's too many toxins. Water hemlock and mercury to start with, and that's a fatal mixture already, but there's other stuff as well that I don't even recognise. Ambrosia and nectar won't be enough. I can't treat this, not without knowing—'

'You have to!'

'I could…' Will rubbed his forehead. 'Clovis, can you—?'

The son of Hypnos nodded and snapped his fingers, murmuring a snatch of song in an ancient tongue. Percy's breathing slowed.

'What did you do?'

'He's in an induced coma,' Will said. His expression was grim. 'It'll buy us some time, but he'll still be brain dead if we don't come up with something.'

'How long do we have?'

'Best guess? Half a day.' Will must have noticed Annabeth's stricken expression, because he added gently, 'It's better than nothing. He would have been gone in five minutes if Clovis hadn't put him to sleep. If I can just figure out what the unknown poisons are, maybe we can come up with a solution—'

'Tartarus,' said a voice from the doorway. Nico stepped into the infirmary. He looked at Annabeth. 'Can't you sense it? The aura around him. He's been poisoned by something from deep in Tartarus. No cure on earth exists for that.'

Annabeth choked back a sob, remembering what Hipponoe had said: I sourced the most insidious venom, the strongest toxins to create this. There is no earthly cure. 'No. There has to be a way.'

Will frowned. 'What about the Golden Fleece? Remember when Thalia's tree was poisoned with venom from Tartarus? The Fleece cured that.'

'We could bring it here!' But even as she said it, despair hollowed out her insides. The Golden Fleece was on the other side of the country. Even if someone set out with it at this very moment, it wasn't likely to arrive in time.

'I'm not sure it'll work,' Clovis said. He looked at Will. 'You said it's his brain, right? The mind's a lot trickier to heal than the body.'

'Unless…' Nico exchanged a significant look with Clovis, who suddenly looked more awake than Annabeth had ever seen him.

'No way,' he said. 'You don't mean…?'

Nico nodded.

'What?' Annabeth asked.

'The Lethe,' Clovis said.

'Seriously?' Will said. 'I've never heard—'

'You're a child of the upper world,' Nico said. 'Underworld magic is different. The Underworld rivers—well, they have some healing properties.'

'Like the Phlegethon,' Annabeth said with a shiver. When she and Percy had been in Tartarus, they'd drunk from the River of Fire. While it had been excruciating, it had also kept them alive.

'Yes,' Nico said. 'The Lethe…well, it's waters specifically target the mind, right? It has to—it cleanses it, wipes away everything, so…'

'You think it could wipe the poison out?' Will asked.

'Nico's right,' Clovis said. 'It's a good idea.'

Annabeth gulped. It made sense that the Lethe could be as powerful as the Phlegethon in healing. But—the Lethe. Percy would…

'Um,' Will said, 'you guys do see the obvious problem with this, don't you?'

Nico and Clovis looked at each other and then at Annabeth, as though leaving the decision to her. Her throat burned when she swallowed, as if she'd ingested a mouthful of Phlegethon water.

The Lethe was where souls went to wipe their memories before rebirth. A single drop could cause severe memory loss. Getting dipped in it…well, Percy had once done that to the Titan Iapetus and made him forget his entire identity.

But they had no other solutions. And Percy was going to die in hours if they didn't come up with anything else.

If this was the only way to save him…well, even if it meant he would forget everything, forget her, she couldn't let him die.

'We have to try,' she said. Her voice sounded hollow in her ears. 'Where are we going to get liquid Lethe, though? Clovis?'

He shook his head. 'I don't have a handy source here. Back in cabin sixteen…well, that's as far away as the Fleece.'

'I can get it,' Nico said. 'I can go to the Underworld. I—it's not as hard for me.'

'Can you get there and back in a few hours?' Annabeth asked.

'Sure,' Nico said. Will narrowed his eyes, but Nico shrugged. 'I'm going alone, it won't take that much energy.'

'Fine,' said Will. 'But be careful.'

'It's the Underworld. I know my way around.' Nico took Will's hand and squeezed it. Then he turned to Annabeth. To her surprise, he put a hand on her shoulder. 'Maybe there's a chance it won't be permanent,' he said. 'Alecto wiped Bianca and my memories in the river of forgetfulness before she too us to the Lotus Casino, but now I remember things from my life before. And—well, Percy told me about Bob.'

Annabeth's chest constricted as it always did when she remembered Bob the Titan, who had died for them in Tartarus. But this time the memory lifted her spirits a little. Bob's memories of his life as Iapetus, before Percy had wiped them, had returned to him eventually, even if he had later chosen to affirm himself as Bob in spite of them.

Nico was right. There was hope.

Annabeth nodded. 'Just save him.'

'That's the plan,' Nico said. And he stepped into the shadow of the door and disappeared into it.

OoOoOoOoOoO

A/N: preciouschildrenofolympus's illustration of Hipponoe and the kelpie can be found here (remove the spaces; FFN won't let me post urls directly): preciouschlidrenofolympus . tumblr post / 164173896410 / heres-the-first-half-of-my-art-for-the-pjo-big