[The Aerie,]
Caitlin Snow had no choice. She sat at the console, the blue glow of Gideon's interface washing over her face, and got to work.
She was a biologist first, a doctor second, and neither discipline had prepared her for metabolic chemistry built around the Speed Force. But after months on Team Flash, she understood the theoretical framework better than almost anyone alive. Gideon's processing speed helped. Each simulated trial that would have taken hours on conventional hardware resolved in seconds, letting her iterate, correct, and iterate again in rapid cycles.
While she worked, Jack occupied himself at the far end of the Aerie. The air around him crackled intermittently, small distortions in the ambient light rippling outward like heat mirages. He was attempting to replicate what Barry Allen had nearly achieved—disrupting temporal continuity, folding it back on itself to create a stable loop. Barry had stumbled into it by accident, and Jack had pulled him out before he'd crossed the threshold, but the attempt had produced useful data. The mechanics were there. The execution needed refinement.
He ran the process again. And again. Each attempt consumed time, chewing through the hours in silence.
At some point during the night, he built Caitlin a Speed Force extraction rig—a compact apparatus wired into the Aerie's power grid that siphoned trace amounts of Speed Force energy into containable samples. She needed them for her tests. He dropped it on the workstation without comment and went back to his own experiments.
The hours bled together. The smell of cold metal and ozone saturated the recycled air.
"Hey." Caitlin's voice was hoarse, barely above a whisper. She rubbed her eyes with the heel of her palm, blinking against the console's glare. "I need to go back. There are still problems with the cellular degradation curve, but if you give me some time, I can solve it."
She swallowed, choosing her next words carefully. "I'll come back tonight. To keep working. Okay?"
Jack turned from his own console. "Tired?"
Caitlin nodded, her eyelids heavy.
"Then sleep here. You can pick it up when you wake."
The words were barely out of his mouth before Caitlin felt the familiar, sickening intrusion—that cold hand sliding behind her thoughts, gripping the reins of her motor functions. Her legs moved without her permission. She walked beside Jack down a narrow corridor deeper into the Aerie, her bare feet silent on the metal floor.
Just let it happen. Fighting makes it worse.
The room was spartan. A wide bed with dark sheets, a single recessed light in the ceiling, the faint hum of the Aerie's climate system pushing warm air through the vents. It smelled like clean linen and the metallic tang of the ship itself.
Caitlin's hands moved on their own. She pulled her pajama top over her head, folded it, set it on the edge of the bed. Stepped out of her pants. Lay down on the mattress, the sheets cool against her bare skin.
The moment her head touched the pillow, exhaustion hit her like a drug. Her eyes fluttered shut. She was asleep in seconds.
Jack lay down beside her, pulled her close, and followed her under.
He didn't know how long he'd been out.
The cold woke him first—a deep, biting chill radiating from the body in his arms. It wasn't the pleasant coolness of someone who ran cold. It was the kind of cold that cracked pipes and killed engines, the temperature of something fundamentally wrong.
Jack opened his eyes.
Caitlin was trembling in his arms, her skin pale and sheened with frost. Her breath came in shallow, ragged bursts that crystallized in the air. The ambient temperature in the room had plummeted; he could see ice forming on the ceiling panels, creeping outward in jagged, fractal patterns. Her eyelids twitched violently, trapped in some nightmare she couldn't surface from.
Killer Frost.
Jack's mouth curved. He didn't pull away. He studied her with the detached fascination of a scientist watching a chrysalis split open.
On Earth Two, Caitlin Snow's doppelgänger had been Killer Frost—a meta with cryokinetic powers and a personality as sharp and merciless as black ice. On this Earth, the same dormant persona had always existed inside Caitlin, buried since childhood, locked behind walls of repressed memory. The particle accelerator, Flashpoint—everyone assumed those were the triggers. The truth was simpler: Killer Frost had always been there, waiting.
And apparently, having her mind forcibly hijacked was enough to rattle the cage door open.
"I was going to use her as leverage," Jack murmured, watching Caitlin's hair frost white at the roots. "A punishment, if you didn't cooperate. But you're waking up on your own." He paused. "Fine. I'll give you a push."
He reached out with his seismic sense—not into the earth, but into Caitlin herself.
(poorly described, I know)
The shift was instantaneous. One moment he was lying in the Aerie. The next, he was somewhere else entirely.
Dim. Indistinct. The edges of the space were soft, like a photograph left in water too long.
A suburban street materialized around him. Afternoon light filtered through clouds that didn't move. In the middle of the road, a car lay on its roof, its windshield shattered, glass scattered across the asphalt like scattered teeth. The smell of gasoline and hot rubber hung in the still air.
A little girl sat on the pavement beside the wreck, staring into a broken side mirror. Her hair was white. Pure, shocking white. Cold radiated from her small body in visible waves, frosting the asphalt in a perfect circle around her. Her pupils were fading, the brown draining out, leaving something pale and empty behind.
"Caitlin, stop it!" A man and woman nearby—her parents, clearly—rushed toward her, voices high and panicked.
The girl turned to look at them.
The vision shattered.
Jack opened his eyes. The room was arctic. His breath hung in thick clouds. Ice coated every surface—walls, ceiling, the sheets beneath them—in a shell of blue-white frost.
In his arms, Caitlin Snow was transforming.
Her hair bleached white from root to tip, the color draining like ink pulled from water. The skin around her eyes darkened, bruise-purple, as though she hadn't slept in weeks. Her lips deepened to a blue so dark it was almost black. The resemblance to Earth Two's Killer Frost was exact—the same severe beauty, the same predatory stillness.
Her eyes snapped open. White. Completely white.
She moved fast.
Whoosh.
A palm strike aimed directly at Jack's face, the air around her hand dense with killing cold. Frost exploded outward from the point of contact, freezing the headboard solid, cracking the metal frame with a sound like a gunshot.
But her wrist never reached him.
Jack caught it mid-swing, his fingers closing around the joint with casual, immovable strength. He'd started his movement after hers and still arrived first. In one fluid motion, he yanked her off the bed and flung her across the room.
Bang.
Killer Frost hit the door hard enough to dent the metal, sliding down to the floor in a heap. The impact would have broken bones in a normal person. She barely grunted.
He's fast. Stronger than he looks. Good. I like a fight.
She rose, naked and unconcerned about it, her white eyes blazing with cold fury. Ice crystallized in both hands, elongating into jagged spikes the length of her forearms. She hurled them in rapid succession—one, two, three, four—each one trailing a comet-tail of frozen mist.
Shhhk. Shhhk. Shhhk. Shhhk.
Jack raised an open palm.
The spikes hit an invisible wall of heat six inches from his skin. They didn't shatter. They simply ceased to exist—melting, evaporating, and dissipating into steam in the span of a heartbeat. The room filled with the sharp, wet smell of flash-boiled ice.
Then he flicked his wrist. Ice spikes materialized in his hand—identical to hers, crystalline and razor-edged—and he threw them back.
Killer Frost sneered.
"Cute." She extended both hands and seized control of the incoming projectiles' temperature, dissolving them the same way he had. The spikes evaporated into nothing between them. "You think I can't do the same trick?"
"Can you do this?"
A dull red glow pulsed inside the last spike, already past her guard.
Killer Frost blinked.
What—
The spike detonated.
BOOM.
The concussive force slammed her backward into the door again, the metal buckling under the impact. She crumpled, sliding down to the floor. Shrapnel wounds opened across her torso and arms—deep, ugly gashes that wept cold instead of blood, the edges of each cut rimmed with frost. She sat slumped against the ruined door, breathing hard.
Killer Frost looked down at herself. The wounds were already closing, cold air hissing from the lacerations as the tissue knit itself back together. Thirty seconds, and her skin was smooth again. Unmarked.
She lifted her gaze to Jack. White eyes, full of venom.
"Nngh." A low, guttural sound escaped her throat. "I'll be back for you."
The purple around her eyes faded. Her lips softened from bruise-blue back to pink. The white drained from her hair in a slow wave, brown reasserting itself strand by strand. Her pupils flickered—white, then hazel, then hazel again—and she blinked, slow and confused.
Caitlin Snow looked down at her own body. Then up at Jack. Then at the destroyed door behind her.
Something happened to me. I don't remember any of it, and that's the worst part.
"What..." She winced, pressing a hand to the small of her back. "What happened? My back is killing me. Did you kick me off the bed?"
"You thrash in your sleep," Jack said, the corner of his mouth lifting. He crossed the room, took her hand, and pulled her to her feet. She was unsteady, so he guided her back to the bed and settled her onto the mattress.
"I thrash?" Caitlin lay in his arms, dazed, trying to piece together a gap in her memory that offered nothing back. She turned her head to study his face. "You're not going to throw me off again, are you?"
"Go back to sleep."
She made a small, noncommittal sound. But sleep was gone. Her pulse drummed in her ears, her skin hyperaware of every point of contact—his arm across her waist, his chest against her back, the steady rhythm of his breathing. The sheets smelled like frost and something faintly metallic, like the aftermath of a storm. She stared at the far wall, wide awake, and pressed her lips together to keep her breathing even.