Disclaimer: Adventure Time belongs to Pendleton Ward/Cartoon Network.

A/N: Thanks to Rinney and Anna for proof-reading! This follows on from '996 Years Ago', but takes place a few years later. Will (eventually) be Marceline/Bubblegum.

As The World Falls Down

Chapter 1 - Maybe

Maybe you'll think of me
When you are all alone
Maybe the one who is waiting for you
Will prove untrue
Then what will you do?
- The Ink Spots: 'Maybe'

"I really don't like this Marcy," Simon whispered to her as the two of them crouched in the ruined storefront. They'd come back to the city to look for supplies that they couldn't find in the wilderness like antiseptic and bandages. Now that she was older, faster and more agile than Simon these days and able to outrun mutants, he'd let her come with him. But the only mutants they'd seen were the ones scattered lifelessly across the square in front of them, torn open like empty cans. The green goo that had seeped from the orifices on their bodies was completely gone, as if whatever had attacked them had taken it... or eaten it.

"But the pharmacy is right over there," Marcy whispered back, pointing at a lopsided green cross hanging in the shattered window of one of the shops on the other side of the square. "Maybe whatever did this is gone... at least this means no mutants, right?"

Simon mentally chewed that over for a few moments, one finger absently circling the large gem on the crown. They needed antiseptic, cuts and gashes were an occupational hazard when scavenging, and with no doctors or hospitals an infected wound could be a death sentence. Not for himself maybe, the crown's magic would protect him from something as mundane as sepsis, but it wouldn't protect Marcy. Maybe they'd even have antibiotics or painkillers in there.

Sighing, he looked down at Marcy as he made up his mind. "I'll go. You stay here and hide in case something appears."

"But Simon," the girl protested. "I'm a better runner, I should go!"

"No," he replied firmly. "If the thing that killed those mutants is about I can fight it with the crown, and you have to run. Promise me you'll run."

"You promised me you wouldn't wear it!" Marcy hissed, half angry and half scared.

Simon sighed again, looking away from the girl's accusing stare. "I know Marcy, but I know I can save us with it. We don't know if you're faster than whatever did this, and we're not taking that chance. Besides," he added, looking back at her. "I'm older, so it should be me taking the risk. If I get eaten, I'll freeze its stomach on the way down."

Marceline couldn't help a small smile at that, though her eyes were worried. "You're so silly, Simon."

He smiled back at her, shifting the pack on his back slightly. "Now get yourself hidden. If we get separated, I'll meet you back at the camp, okay?"

"Be careful Simon," she replied, crouching down behind the ruined wall and staying perfectly still. He didn't respond, but patted her head lightly then carefully crept out into the ruined square, moving slowly and cautiously.

Nothing stirred except faint puffs of ash that Simon's feet kicked up no matter how carefully he stepped. It was nearly ten years since the bombs had dropped, and the cities were still coated in ashes from the fires that had burned them out. He stepped over a dead mutant, nerves on edge in case it was a trap, but it didn't move. He paused to take a closer look, wondering if this thing had ever been human or if it was purely a product of the bombs. Apart from the humanoid shape, there was nothing else about it to suggest that it had been a person.

It looked like it had been torn apart by vicious claws that had hooked into the orifices on its chest and pulled it apart, inside it seemed to be hollow without a trace of the green fluid that normally spilled out of them. Warily, Simon poked at one of its motionless limbs with the toe of his boot, and it cracked and crumbled like eggshells. Shuddering, he quickly moved on towards the pharmacy.

The door was still on its hinges, but the lock had been smashed, whether from the bomb blast or looters Simon didn't know. There hadn't been many of the latter; most survivors had gone for grocery stores first before succumbing to radiation sickness. He still didn't know how Marceline had survived that, how she was still perfectly fine in an irradiated wasteland, but he didn't question it. Marceline had told him her father was a demon, which sounded insane, but then again Simon owned a magic crown which talked to him so he didn't really have room to judge.

At first it looked like the shelves were empty, but that wasn't unusual. Given the force of the blasts and the earth tremors that had followed, it was more unusual to find things where they'd been left before the war. Crouching down, Simon carefully shifted some of the rubble, mostly fallen ceiling tiles and plaster, looking for anything that resembled medical supplies. Finding a plastic bottle, he wiped one thumb across the dusty label to reveal the name 'Tylenol', and slipped it into a pocket. He was about to lift another tile when he heard a gargling shriek.

Outside in the square, a mutant flew from a side street to land in the centre of the plaza, bouncing and skidding to a halt. Simon froze in place, unconsciously holding his breath as it got back to its feet. The creatures had no faces so it was impossible to guess their mood, but from the way it started to rapidly shuffle away it was plain that something had attacked it. And that it was frightened.

"Oh mother, mother, mother…" Simon muttered under his breath, hoping Marceline would keep hidden. If whatever had attacked the mutant came after it, hopefully it would be too distracted to notice them.

The mutant had barely taken three steps when the dark figure swooped down on it like a bird of prey, tattered robes trailing from its thin arms like wings. It took a moment for Simon to realise that the arms weren't just thin, they were skeletal. Ragged, leathery flesh hung off its forearms to expose bones which looked like they were only barely held together by a few remaining tendons.

The strength of those arms belied their fragile appearance as bony fingers sank into one of the oozing holes in the mutant's flesh and pulled. Simon watched in silent horror as the skeleton creature tore the mutant in half like an over-ripe melon and thrust its head forward to gulp down the green slime that had filled its body cavity. The mutant kept struggling and moaning until the last glowing drop had been drained from it, and Simon felt his stomach heave in nausea. Fighting down the urge to vomit, he slowly crept over to the broken window, trying to catch sight of Marcy, hoping she wouldn't move.

The girl was still crouched in the rubble where he'd left her, watching the creature with horrified fascination. She hadn't made a sound or shifted from her position despite what she'd seen, and Simon felt a surge of paternal pride despite their dire situation. As if she'd sensed his gaze, she looked towards him, her eyes wide and frightened, and he gestured to keep hidden, hoping that this... this thing would go off in search of more mutants to hunt. It was already getting back to its feet.

Throwing the mutant's drained husk aside with contemptuous ease, the creature stretched to its full height. It was massive, towering at least eight feet from the ground and crowned with a set of curling horns that added an extra foot to its height. It was hard to tell through the voluminous robes it wore, but it looked humanoid, its arms certainly had a human bone structure, with the exception of the vicious claws it had instead of fingertips.

The horned head swung from side to side as it appeared to scent the air like a wolf, and Simon saw the glint of bone at its jaw as well. He was reminded of a book of religious medieval woodcuts that he'd possessed in his former life, the creature in front of him only needed a scythe to be the Grim Reaper that had featured in the images.

'Just go away,' he thought desperately. 'Go away and leave us alone whatever you are. We are never coming back here if we get out of this...'

Marceline never made a sound, never moved a muscle, but to Simon's horror the creature's head snapped directly towards her as if it had sensed her presence, and began to drift over to where she was hidden, somehow levitating instead of walking. Simon's reaction was instinctive.

"Hey! You!" The creature halted as Simon sprung up from his hiding place and hurled a piece of plaster at it, which bounced off its back harmlessly. "Come get me you abomination!"

The creature didn't seem to turn, its head simply swivelled a hundred and eighty degrees to glare at him while its arms were still stretched out towards where Marcy was hidden. The skin of its face flapped gently from the movement as if it was only loosely attached, and around the mouth it had been torn away to reveal its jawbone and jagged teeth. But the eyes were the worst, the empty black sockets of a skull in which lurid green fire danced with malign intelligence.

Simon felt his limbs freeze beneath the creature's gaze, seeing its jaw moving spasmodically as if it was speaking. There was an odd buzzing in his ears, like a faint, badly-tuned radio, but it sounded almost like words. The green flames in the creature's eye sockets narrowed to sparks, and then its gaze moved downwards and to the side, fixing on the crown at Simon's belt. For a few seconds it stared at it, almost as if it recognised it, then with a disdainful snort its head snapped back round towards Marceline as it swept down towards her.

The girl screamed as the creature hauled her out from her hiding place by her hair, struggling madly and kicking at it. Without even thinking about it, Simon snapped the crown from his belt and placed it on his head, and the world lit up with the beauty of sparkling frost as the power of winter surged through him, raising him into the air as his hair and beard grew as long as a midwinter night.

"Let her go!" He aimed a blast of icy wind at the creature, struggling to focus on what he was doing. He had to save Marceline no no no he had to bathe the world in ice and snow and dance in the drifting flakes forget the girl forget her forget her. Gritting his teeth and blocking out the crown's voice, he kept its power focused on the creature. Which appeared completely indifferent as frost rimed its robes and bones. It made a fist with its free hand, which burst into toxic green flame, and with a scornful flick of its wrist it batted Simon away with as much ease as it had thrown the dead mutant earlier.

Hitting the wall of the pharmacy hard, Simon slid down to the pavement, dazed. Shaking his head, he blasted himself back into the air, about to bodyslam into the creature in the hope that it would drop Marcy. It hadn't even shifted its gaze from the girl, lifting her high into the air with one hand and drawing the other back…

then everything seemed to blur like a time-lapse recording. Simon blinked, and the creature's claws slashed forwards to open Marceline's throat with a spray of scarlet as her struggles ended with a gurgle. He blinked again, and her lifeless body lay in a pool of blood at the creature's feet. He opened his mouth to scream, his eyes filling with tears but as the first ones trickled from his eyes they froze solid.

'That's what will happen,' the crown said, matter-of-factly. Simon could feel its presence clearly, coiling around him like a lover. 'But not yet.'

Simon blinked again, and the horrific vision rewound itself. Marceline was back in the creature's grasp, still struggling, but its claws were starting to swing towards her. This time however, everything seemed to be happening in slow motion.

"TELL ME HOW TO STOP IT!" he screamed as the chill power of the crown pressed against him, its cool breath breezing past his ear.

'Oh, that's easy,' it purred seductively. 'Just give yourself to me, and together we can save her…'

Inch by inch the hooked talons fell towards Marceline's throat and Simon knew he had no choice. Frozen tears fell from his eyes like crystals as he made a silent plea for forgiveness to whatever deity might be listening, and to Marceline herself. "Do it then," he whispered. "Save her." He closed his eyes, and when he opened them again he was no longer Simon Petrikov.

Marceline struggled and kicked desperately in the monster's grasp, her breath coming in rapid, terrified gasps as she tried to free herself. It was no use; the cold skeletal fingers held her tightly, burning eyes staring into hers as she smelled the charnel-house reek of its breath. She didn't even notice that Simon had put the crown on, barely feeling the cold rush of winter wind as it buffeted the creature. One of its hands ignited with sickly green fire and as it drew it back and flexed its claws she knew it was going to kill her.

Then, with a crash and shatter of bone, a javelin of solid ice took the arm the creature was holding her with off at the shoulder, and she fell to the ground with a thud.

"STOP TOUCHING MY THINGS!" Simon's voice was barely recognisable, a crazed, cracked shriek. Marceline looked up to see him hovering in the air with the crown on his head as snow whipped around him in a frosty corona. The creature's severed arm flopped and flailed on the ground like a landed fish as Marceline pushed herself backwards on her hands and knees, but the skeletal monster seemed to have forgotten her. It picked up its arm from the ground and reattached it, seemingly with ease, but then was blasted with hailstones the size of marbles.

"I AM THE KING OF ICE AND SNOW, AND I COMMAND YOU TO GET LOST!" Simon was still raining the unfettered power of the crown down upon the creature, layering it in a thick rime of ice as it raised flaming hands above its head and hurled a green fireball at him. The whirling snow extinguished it harmlessly as Simon laughed madly, jagged teeth glinting as he continued to cover the creature with ice. Before it could be completely encased, its monstrous form dissolved into shadow, spilling out of a gap in the ice like smoke and reforming a short distance away.

This time it didn't renew its attack, and simply watched Simon instead, who was still laughing as the snow whirling around him became jagged hail. Then Marceline realised that it wasn't looking at him at all, its gaze was fixed on the crown. Its head snapped round to look at her and although the missing skin on its face gave it a permanent skeleton grin, she could have sworn the edges of the tattered flesh tugged upwards in a smile. What it did next confused her completely – it levitated into the air and moved away, disappearing into the street it had originally emerged from without further ado, leaving her with Simon.

"Yes! Run from me!" Simon snarled, even though the creature's retreat could hardly be called a run. "Run from the Ice King!" He threw back his head and laughed as his glasses went flying, the hailstorm spreading out around him as he twirled in the air in some kind of maddened dance. Diving back around the wall she'd been hiding behind earlier as she was pelted with hail, Marceline scrabbled desperately in the rubble until she found a fist-sized chunk of concrete, and hurled it directly at the crown perched on Simon's head.

She was a good shot, and it hit the crown with a clang of metal, knocking it off Simon's head to land a few feet away, rolling gently in a patch of snow. But for the first time, knocking it off did nothing, the snow didn't stop and Simon didn't fall, though he did give an irritated yell.

"Gunther! Stop interfering with my victory dance!" Simon snapped, his voice still scratchy and harsh, not like Simon's at all. Landing beside the crown, he picked it up, dusted it off, and put it back on. His appearance hadn't changed at all, his hair and beard still reaching almost to his knees, his glasses forgotten. Running forwards, Marceline grabbed his arm and tugged at it desperately.

"Simon! Come back! It's gone now, you don't need the crown. Come back," she begged, clinging to him as she stared into his eyes and willed him to remember.

"Who?" he asked with a frown. "You're talking crazy Gunther. Stop it and go build a snowman to commemorate my glorious victory. Hey!"

Marceline had thrown herself at him, hugging him tightly in the hope that it might snap him out of it. "You're Simon Petrikov!" she half-shouted. "You used to study old things before the war and you had a fiancée called Betty and I'm Marceline, not Gunther!"

"Only thing getting old here is you, Gunther." Simon shoved her away roughly, but Marceline sprang at him and swatted the crown away once more, this time trying to pull him back as he reached for it.

"No!" Marceline's voice was almost a scream. "Leave it alone, you need to remember, you need to…" Before she could finish, he pushed her away with one arm and brought the other around to deliver a stinging, backhanded slap to her face which knocked her to the ground.

"Knock it off; you're really starting to get on my nerves." Simon growled as he retrieved the crown and put it back on.

Marceline didn't reply or get up, one hand clasped to her cheek numbly. Simon had never, never struck her. And when he looked back at her with the dispassionate eyes of a stranger, she knew he was gone.

The man that had been Simon recoiled slightly as the shaking girl pulled her arms around herself with a heartbroken wail, tears welling in her eyes. He looked down at her as she sobbed, not showing the slightest glimmer of compassion, only embarrassment at the scene she was making. "Gunther, stop that noise right now!" he ordered sharply. "Stop it!" Folding his arms in annoyance as she ignored him, he gave a frustrated sigh. "Fine then. I'm out of here. Come find me when you're not a whiny little baby any more." Turning his back on her, he launched himself into the sky and headed north to the siren song of the frozen mountains, leaving Marceline alone in the ruined city.

She was eleven.