Anna's four the first time she hears it.

"Your sister's a freak."

Elsa, seven and crouched by the ice delivery cart in the courtyard – and within earshot – hunches her shoulder high to disguise the red that rushes into her pale face. Anna frowns. "That's mean."

The boy, much older than both of them, sticks out his tongue. "Well she is. You don't think all that stuff she does is weird?"

Last year, when Elsa touched the corner of the lake and froze the entire thing solid for iceskating, Anna didn't think it was weird. She thought it was beautiful, watching the cold rush over the deep, dark water. Or at Christmas, when they opened presents with snow falling around them; Anna didn't think it was weird at all.

Their parents get wind of this, and Anna never sees the boy again. Or much of anyone, really. Papa closes the courtyards gates to all children and passerby: trading partners and visiting guests only.

"But why?" Anna whines. "He was just being a bully, right, Papa? Elsa's not a freak."

"No," says their father, looking anxiously at Elsa across the dining table. She determinedly stares at her food. "No, of course. Other people – well, honey, they're not as accepting as we are. They don't understand."

Anna truly pities them.

There's no name; the family and staff call it "Elsa's power," and there are no books to answer her questions once Anna learns to read. So she spends her childhood wondering – if there are others like Elsa. If their hair is the color the snow that flies from their fingertips, or if they weave snowflakes into it, too. If their voices lilt with the permanent scratch of the cold.

She and Elsa, when they're not schooling, build snowmen – sometimes just one, sometimes an entire battalion – and ice-skate in the downstairs foyer. They braid each other's hair and play dress-up and make cookies and hot cocoa together. "Do you wanna build a snowman?" becomes a household phrase, one met with twinkling eyes from Elsa and playful, secret smiles from the staff.

Anna falls in love with the stars, and the skies. Often, she'll stay up late at night, gazing at the aurora as its greenish-blueish glow ribbons across the ink black sky.

One night, even after her moan of, "But the sky's awake, so I'm awake," Elsa won't budge. So she crooks a finger and lifts her sister's eyelid. Elsa smiles.

"Do you wanna build a snowman?"

Elsa moves rooms.

Anna isn't sure what happens. Mama and Papa are dodge every question, and there is unnerving radio silence from Elsa. No answers to Anna's knocks, her pleas of that old phrase – nothing at all.

Sometimes, Anna realizes that Elsa could be dead behind that door, and no one would know it.

One night, when Anna is thirteen, she falls asleep outside of Elsa's room after a night of empty, answerless begging.

She wakes up to something smooth and cold passing over her hand, like a spirit. When she wakes up enough to look down, it's a hand – a gloved hand, covered in ice blue satin. Coming from behind Elsa's door.

She hears her sister cry, softly, and holds still until Elsa's hand and arm finally retreat.

"Elsa's hands are really cold."

"What?" her father asks, startled as he looks up from his cup of tea. "What do you mean?"

"She – nothing." Anna isn't ready to breach the secrecy of their private moment. Not yet. "She...pushed me away from her door yesterday. It felt like she had ice under those gloves."

"Oh." Papa pales. "I see."

She waits for an answer, but he turns away instead. Anna should be used to it by now – people shutting her out – but still, she resents him. Resents them both.

Anna hears the yelling. The whole castle must.

"It's getting stronger!"

It's been so long that she almost doesn't recognize the voice: Elsa.

"I'm scared," her sister continues, stricken. The whisper of their parents shushing her meets Anna's ears as she mounts the stairs. At the end of the hall, Elsa's door is open.

She has never seen that door open. Ever.

"You need to remain calm," Papa begins, but there's a sharp cry. Elsa again.

"No!" she yells. "Please." A pregnant pause. Anna strains.

"You don't understand. I feel like...like I wanna hurt you."

An icicle skewers Anna's stomach.

She has nightmares all week. She sees Elsa and their parents, and how Elsa kills them. Sometimes with a knife, sometimes with a rock, and sometimes hanging them in the courtyard gallows. She sees herself and her mouth wide open, frozen in a scream – of horror, of indignation, to plead with Elsa, she's not sure. But she's always screaming.

The blood is vivid. It stains her dreams a deep, crimson red.

The month after, their parents announce that they'll be going on a sailing trip.

Anna counts the days until they come back. The days until her salvation.

With their parents gone and Elsa approaching eighteen, she runs the castle for the weeks their parents are out. She's gotten remarkably pretty with age – breathtaking, really, with her intricately woven white hair and those expression blue eyes. The kingdom runs smoothly with her at the helm, and she maintains a calm that unnerves Anna.

She doesn't like being alone with Elsa. She doesn't feel safe being the only other royalty in the castle with her. Not even a year ago, she would have done anything to see her sister; now, she dreads the moment Elsa wakes up. The moment she hears Elsa's footsteps moving along the stone hall, past Anna's bedroom.

When their parents return, they commend Elsa for the work she's done. She accepts the praise with a small, complacent smile; Anna buries her face in Papa's chest as she hugs him so Elsa can't see the relief.

For Elsa's eighteenth birthday party, their parents throw a grand bash and open the courtyard gates to everyone for the day.

Elsa looks happier than she has in years as her father crowns her, and dons her maroon birthday cloak with shining pride.

As Anna watching the crowning, a hand catches her shoulder.

"Hey," a slimy voice says, "you're the princess, aren't you?"

"Yeah." She frowns, shaking him off – a man, not much older than she. A peasant, by the looks of his dirty, sweaty coat and rags. "Why?"

"Is it true they closed the gates 'cause you're sister's a witch?"

"What? That's ridiculous." She recalls what her father told her all those years ago. "Papa didn't like that other kids were being mean to us."

He utters an unctuous laugh. "Yeah, I'll bet they were; what with your sister's freaky ice magic, how couldn't they?"

She rolls her eyes at his crazy talk. Then, he raises his voice above the chatter of the crowd and yells, "Why don't you show us!?"

Elsa yanks away from Papa, startled. He shields her with his hand.

"Excuse me, sir," he calls back, "this is a crowning ceremony –"

"I know what it is, dolt. What I'm asking is how about your daughter freeze the lake like she did that one year? Let all the kids go iceskating again –"

"Guards!" Mama crows. She points a shaky finger. "Escort that man out. Now."

"Hey," another voice joins, "that's true, huh? How come she doesn't do that anymore?"

"It's 'cause it's unnatural!" someone, across the crowd, rejoins. "If you ask me, good riddance! Last thing we need is witchcraft in this kingdom."

"That's ENOUGH!" Papa thunders, red in the face. "Everyone out – this celebration is over."

A disturbed cry of protest shudders across the crowd. "Aw, cmon," the man yells, "don't punish us because of your freak daughter!"

"Shut up," Anna barks, striking him. He beams a crooked, toothless smile at her, and she has never hated anyone more. "Well? Get out of here! Go! GO!"

The guards rush into the uproarious crowd, guiding everyone toward the gates. She watches them pour out of the gate, and it's only when it booms closed that she begins to cry.

Elsa is shaking, white as a ghost. When Papa reaches a hand to comfort her, she darts away, back into the castle. She's ripped the tiara from her hair.

Anna doesn't hear from her for so long after that.

Anna is nearly sixteen when she hears the knock.

Her poor, baffled heart gives an optimistic flutter as she, half-asleep, opens her door.

"Elsa…?"

The servant bites her lip. "Oh, Princess Anna."

They bury their parents on the top of the hill where they met, in the next kingdom over.

The black satin curtain that falls over their portrait back in the castle feels like it opens in Anna's gut – a trembling, empty space, ripped out of her.

The staff doesn't let her in the kitchen, where they died. They don't let her see what she already knows: that there's still ice streaked in jagged, menacing patterns along the walls and floors.

"Elsa?"

"Go away."

"Elsa –" Anna chokes back her cry. Not now. "Please. Let me in."

"Go away."

"I know you didn't – mean to," she stutters out, unsure how much of it she actually believes. "I know it's the ice magic. Okay?"

No reply.

"Please," she says one more time, but there's no point.

Elsa's silence is answer enough.

About two months later, Elsa kills a cook.

The story goes, he was setting the plates for dinner when Elsa tried to help and accidentally froze him solid. But Anna knows it's for her benefit; talk around the castle after that tells her that Elsa was all the way across the dining table, when she calmly raised her hand and shot him with an icy blast. Then another, as he scrambled away in fright.

They say she was smiling as she watched his icy corpse smash to pieces on the floor.

Anna stops trying to talk to Elsa. She stops going near that door, or even that room in the castle. She dreams of the cook's face, preserved in that final surprised moment, as it broke against the hardwood floor. She dreams of Elsa's smile.

At night, she hears Elsa pacing, and barricades the door. She hardly leaves her room anymore; beneath the crack of the door, she can see the ice slowly crystallizing beneath Elsa's feet as she wanders the castle, sometimes all night. Sometimes frost will climb up the wood of the door; in the morning, it's freezing no matter where you go.

She hears Elsa muttering, too. "Conceal, don't feel." "Control it, control it, Elsa." She hears how deep and unsettling Elsa's voice has gotten – how menacing she sounds, even as she brokenly whispers incantations to herself.

One night, it stops. Just like that.

Anna will later learn that, when Elsa turned nineteen, her resolve finally crumbled.

She gave in.

On Elsa's nineteenth birthday, there is no celebration.

The entire castle is frozen from the inside out. And that's not even the most terrifying part.

When Anna looks out her window, as the staff helplessly tries to scrape the ice off of the walls and eager opportunists gather shavings to sell, she sees Elsa down by the shore of a shadowy, isolated shore of the lake.

She stares at the water for the longest time. Then, as she turns away, an enormous bloom of ice rockets out across the water, consuming it in a thick, impenetrable layer. It takes no time at all.

Calmly, she looks up at Anna's window, right into her sister's eyes, and waves.

Anna doesn't recognize her.

After that, the sun never comes out anymore.

The lake stays frozen, even on the hottest summer days. Kids try to ice-skate on it and go missing; no ship can sail in or out, and half of Arendale's trading partners cut ties.

The castle stops freezing, but the landscape stays that way: frozen solid. Like there's no hope.

One night, not long before Anna turns eighteen, Elsa hacks up her chest and neck with a dull knife from the kitchen.

The cooks, returning from their break, find her bloody and sobbing on the cold floor, with the blade shakily pointed at her heart and blood spilled all over the front of her gown. They manage to wrestle it away from her, before she screams back into life and kicks one of them so firmly in the head that he goes flying to the ground and breaks his skull. The surviving cook resigns the very next day. No one learns what really happened in that kitchen.

She's taken to the infirmary, and restrained, where she moans all night about how much she hurts. By morning, every inch of the room is covered in ice.

"Going away?"

Right down the hall. Anna pulls the covers closer to her body.

She's eighteen, but feels eight all over again.

"You can't send me away," Elsa says – in that unsettling, unmoving voice. "I'm the queen."

"Well, Princess, technically you're not the queen until your coronation day, which remains another month –"

"You can't send me away," she interrupts, harder now. Speaking fact now. "You can't."

"Elsa, I'm afraid we have to."

"Do enlighten me."

"You're...beginning to frighten the staff, if I may. Myself included."

"Is that so?"

"Yes, ma'am. And we –"

A loud, sickening choke. Anna stuffs her blanket into her mouth to mask her shout; a body softly crumples to the floor not moments later.

Tears burn her eyes, and that's when her door opens.

"Anna?"

Elsa looks...different. Darker. Her hair is still white, but something about her looks heavier. More in shadow. Her eyes are cold and calculated as they drink in the sight of her little sister, trembling in her bed.

"It's okay," Elsa says calmly, coming toward Anna, who has no choice but to hold her breath as Elsa gathers her into her ice cold arms. "It's okay, Anna. Mama and Papa can't separate us anymore. I'm here now."

The blanket slips from Anna's mouth, and she can't stop herself: "Is that why you killed them?"

Elsa just smiles, smoothing Anna's hair. Her finger wraps the solitary white streak around her finger; the collar of her gown is low-cut, revealing the deep gouges from the knife that now scar her chest.

Later, when Anna sneaks out to get a glass of water, Elsa has left the servant's body in the hall. A bloody icicle is lodged straight through his throat.

Something loudly thwacks her window, ripping Anna out of sleep.

She rushes down into the courtyard without being prompted, nightgown fluttering around her ankles, and finds Elsa with the gates frozen shut. An explosion of ice jets out from where she stands.

She freezing birds that fly by; their stiff, icy bodies crash into the walls of the castle and burst in sticky, bloody icicles.

"ELSA!" Anna wails. Her sister whirls around, wild. "Elsa, stop this –"

Elsa launches a piercing shard of magic at Anna; it strikes the arch beside her, frighteningly close to Anna's face.

More birds come down. A dove strikes Anna in the head and her vision sharply blurs. Elsa watches Anna fight to come closer as more and more birds bomb the castle. Beyond the gate, she hears citizens screaming.

"Stop," Anna begs, seizing Elsa's stiff shoulders. "For the love of God, stop this. Please."

Elsa falters. Her eyes, now the dark blue of an ocean, grow wet. "I don't know what's happening," she whispers helplessly – a glimpse at who she used to be.

"Listen to me: we can stop this together. You don't have to become this."

"But – Anna," Elsa hiccups. The birds are unbearable to listen to – screaming out their final squawks before plummeting. "I don't know how to stop it."

Anna grasps Elsa's raised hand, firmly crunching it to her sister's side. The falling bodies finally, finally, cease after a moment, and Elsa starts quivering.

"You don't have to live in fear," Anna soothes. "I'm right here with you."

Suddenly, her sister's eyes fade away, just like that – like a cloud moving over the sun.

"Elsa," Anna says, to a blank stare. To eyes that hold and see nothing. Her heart jackhammers faster. "Elsa. Hey. You in there?"

Elsa's hand breaks from Anna's and crashes into the side of Anna's face, so hard that she can see no more.

"Leave us alone."

When Anna wakes, Elsa is gone.

Servants rush out to help her up, and Anna can't talk. The entire half of her head is completely numb.

She just makes out Elsa – upstairs and watching from her window – before she blacks out again.

Elsa's hand, bare for the first time in years, leaves a frostbitten handprint on Anna's face.

No one takes about the birds again. No one dares to venture it. The cleanup for the blood and bodies enlists nearly half the staff, to get the courtyard spotless for Elsa's coronation.

When the day comes, she humbly accepts the tiara and crowned jewels; she smiles sweetly at every stranger he walks by and, at the party after, agrees to dance with a prince from the Southern Isles. He's glib and handsome and just as callous and deliberate as Elsa. They get along swimmingly.

Anna sits in the far corner of the room, legs folded. The right side of her face is still bandaged. She talks to no one and never takes her eyes off of her sister.

She hears a duke compliment the beauty of the ice sculpture – done by Elsa, of course – and wants to cry.

Hans is the man's name. He's a year younger than Elsa, and pretends that Anna doesn't exist, even when he announces his engagement to Elsa a few months later.

The kingdom is thrilled to see such a virile and capable young man becoming their king. Anna thinks both of them defile the thrones by daring to even breathe on them.

Two weeks before they're to be married, the Duke of Weselton is murdered on the docks, his throat slit and his corpse pinned to the helm of his shirt by a thin sheet of ice. Weselton, outraged, threatens a formal declaration of war, and Hans is delighted by it – in his mind, war is a new obstacle to tackle, and the perfect opportunity to gain rever from his new subjects. Elsa meets the threat with a cool smile.

"Go ahead."

Anna knows, after all, this was her intention.

Hans is found dead the day after the wedding.

Elsa cries assassination, and Arendale declares war upon Weselton. It's a bloodbath, with hundreds of thousands inexperienced children and teenagers enlisting against the trained, powerful Weselton army.

Not that Elsa minds.

"Sacrifice is necessary," she tells her panicked, frantic subjects. "They killed my husband, and our beloved King – they need to understand that we won't take that lying down."

By now, her eyes are nearly black.

One night, Weselton storms the beach of the lake with cannons and bayonets, slaughtering the people who live in the port by the dozen. Elsa slips into Anna's bedroom while Anna has her face pressed against her window, sobbing as she watches. Screams and explosions penetrate the glass.

Elsa pulls Anna back, to cradle her against her chest.

"Shh," she murmurs, petting that one white strand again. She watches the chaos, too, with dry, dark eyes; flames from the cannonfire explode in her pitch-black irises. "It's okay. I won't let them hurt you."

Anna can't hear a heartbeat. A sign that her sister is still alive – or still human.

The Weselton army, camped in the port, tries to negotiate, but Elsa doesn't budge. They scream demands over the wall and the only answer is an echo against the stone. It's like this for three days.

Elsa dismisses the staff. Every last one of them – not that they don't seem eager to go. The castle is unnaturally quiet.

"Just you and me now," Elsa murmurs that night, where Anna's huddled and shaking in her bed. "We're finally together."

"Please leave me alone," Anna whispers.

"I can't."

"You need to stop this."

"I can't do that, either." Elsa pulls back, smiling. She kisses Anna's forehead. "Don't you see? Not now. Not when everything's so perfect."

Anna bursts into tears and she doesn't want to, but she clings to Elsa anyways as she cries. Her sister smiles into Anna's hair.

It's the last day.

Anna knows that, even before the Weselton soldiers climb the walls and storm the castle. Even before Elsa rises from her spot in the corner – she never sleeps anymore – and floats down the stairs. She knows that this is where it has to end.

Bodies start dropping like flies in the foyer. Men screaming, guns exploding; the sharp sound of ice forming and slicing into them rings out.

Anna rushes down the stairs, two at a time, her heart in her throat.

"ELSA!"

Elsa is killing them. All of them, one at a time. She brutalizes them, rips them apart, with her ice. With her bare hands. She freezes some of them and forces them to watch.

Blood. Everywhere. Anna slips in it and bangs her knees.

"Elsa," she screams again, over the deafening thunder of death. "Elsa, stop it! STOP!"

Thud. Thud. Thud.

"ELSA –"

"ENOUGH," Elsa howls.

Shocking silence snaps over the entire room.

Anna gags; all around them are bodies. Twisted and mutilated, their faces surprised and horrified and in agony. The front of Elsa's dress, once the palest of whites, is completely red from the blood.

She stares at Anna through her hair, hanging in her face. Her eyes have no sclera. They're as black as night.

Anna's knees buckle.

Elsa stares at her for the longest time, in that sea of bodies. Then, trembling, she lowers the neck of her dress.

There's an empty cavity where her heart should be. No more scars, or even skin to be scarred – just a gaping hole.

"Don't you see," she rasps, raw. "I can't."

Anna tries to scream, and ice fills her throat.