A/N: I wrote like 95% of this before we saw the Season 4 trailer, so Caitlin should still kind of look like what she did in the Season 3 finale instead of the normal-looking-but-completely-badass version we saw in the trailer.

A huge explosion outside rocked the abandoned warehouse that Barry had currently been held captive in for a few hours now. One of the Thinker's henchmen had injected him with something similar to what Solovar in Gorilla City had. Next thing he knew, he was strapped to an uncomfortable, metal chair with his head attached to some scary device littered with wires. Something about this whole setup was preventing him from using his powers, not to mention his head was throbbing.

The speedster could hear a lot of commotion outside, but he couldn't make out what any of it was. It sounded like a lot of shouting and weapons being fired. Another explosion was then set off, breaking Barry from his thoughts. This time the explosion hit the warehouse head on, causing the whole place to quickly catch on fire.

Barry fidgeted and jostled around in his seat, trying to find a way to free himself, but the restraints were too strong and he was too weak. He coughed and his eyes were beginning to water as the flames around him rapidly got higher and closer, and the resulting smoke rose and entered his lungs.

He was drenched in sweat with the fire already nicking at his suit when suddenly the air around him cooled, and the flames extinguished seemingly into thin air. Barry stared at the area astonished by the effect, thinking that he was hallucinating, until he saw a woman walking determinedly towards him, her hair as white as snow and by contrast her lips as red as a freshly picked apple.

"Cait," he breathed out, a smile breaking out on his face in relief as his personal physician came closer to him.

The corners of her lips turned downward, noticing the burns and lacerations on Barry's body. "Are you okay?" she asked gently, using her powers to freeze his restraints and break them off.

"Fine now," he answered distractedly, unable to stop himself from looking at her like she was an angel sent from heaven as she helped him take the scary, wired-infested cap off his head, which stopped the throbbing he was feeling instantaneously, though he felt a bit woozy.

"What was he doing to you?" she asked, her voice laced with concern.

Barry lightly shrugged, his eyes never wavering from the woman in front of him as she traced some of his wounds, her expert eyes analyzing them.

There had been a moment there, in the fire, when the smoke was suffocating his lungs and the flames were spreading closer and closer, when he thought he was going to die. He had thought of everyone - the people of the city he'd be leaving behind and everyone back at STAR labs - but Caitlin's face stuck out among them all, clearer and more poignant, providing him tranquility in a frightening time. It made him think of how much she was always there for him, despite everything they've been through together. How they could rely on each other and be each other's rock. How she made him feel better by just being around her. That he loved her. The realization hit him like he got struck by lightning all over again - that Caitlin was essentially everything he had always needed, and he felt so stupid for taking so long to notice.

"Let's get you back to STAR labs so that I can properly assess you," she said, helping him get up on his feet.

Despite the throbbing of his head subsiding, Barry felt himself becoming more and more lethargic. His eyes were growing heavier by the second and his body was becoming slack, causing his knees to give.

"We got you, man," another voice said as their arms caught him from falling.

"Cisco?" he murmured in surprise when he turned to see that his other best friend was beside him dressed in the Vibe costume. When did he get here?

"Yeah, I'm here too, dude," he remarked, smirking at Barry knowingly. "Let's get you back," Cisco continued, opening a portal just as Barry passed out.

…

Barry's eyes fluttered open, immediately catching the gentle gaze of Caitlin Snow.

"Hey," she let out softly, her lips quirked into an easy smile.

Barry's stomach squirmed pleasantly at the sight; waking up to Caitlin's friendly face was always comforting, her presence making him feel taken care of and secure. "Hey," he responded back hoarsely, his throat still a tad rough from both sleep and the smoke.

"How are you feeling?"

"Alright," he replied casually, carefully sitting up in the bed. "What happened? Did I pass out?"

Caitlin sat down on the side of his cot. "Yes, probably from the excess carbon monoxide you inhaled as well as it being an after-effect from whatever Devoe had you hooked up to."

Barry nodded his head absentmindedly, trying to force himself to listen to the information but he was simply spellbound by his doctor. Even when her hair was white and her tone was clipped with professionalism, a tender warmness still radiated from her as her lips moved around her words. And with one look into her chocolate brown eyes, he could see the compassion and care she held for him and it tugged at his heart. How could he not have realized this all before?

"I don't think he did anything to your mind," Caitlin continued. "At least from the tests I've run, it seems like he was just trying to absorb everything you know but not necessarily manipulate it."

Barry didn't respond, just dazedly looked at Caitlin.

The doctor laid a comforting hand on his arm. "Are you sure you are okay? You seem a little disoriented still," she noted, glancing him over with concern, no doubt noticing that his eyes still had a far-away look to them.

He didn't know what came over him, whether it was his natural adrenaline or the feel of the speedforce coursing back through his body after being dormant for hours or what, but he leaned over and pressed his lips to hers, kissing her softly.

He could tell she was definitely shocked, even timid about it at first, since she didn't immediately kiss him back. He couldn't blame her; they had been friends for so long and they never gave each other any indication that they had feelings about each other this way. But moments later, just as he was about to pull away, Caitlin pushed aside all her doubts and shyness as she started to kiss him back.

Kissing Caitlin felt like greedily lapping up an ice pop - so cold yet delicious tasting. Her lips were chilled but it only excited him further, enticing him to delve deeper.

He pushed his tongue against her closed mouth, silently asking for entry. It took an agonizing second, but she eventually parted her lips for his tongue to enter, and when her tongue finally joined in, sweeping around his, her hands pulling and tugging his hair to get the angle of their kiss just right, it caused the young speedster to let out a groan of pleasure.

However, the euphoria was short lived when Barry was forced to detach himself from his personal physician, sputtering in shock. He looked down only to witness his tongue encased in ice.

Caitlin's eyes went wide. "Vibrate, vibrate!" she hollered, her tone scolding him yet it was double laced with worry and guilt. He immediately vibrated himself until the ice melted away.

"I'm so sorry, Barry," she apologized, the worry lines on her forehead were deep as she took long strides away from him.

He looked at her dumbfounded for a moment before the corners of his mouth raised and a laugh escaped them.

Caitlin looked at Barry incredulously. "How can you be laughing? I could have killed you!"

He looked at her fondly with no trace of anger or irritation evident on his face. "Was that your first time kissing someone since your powers fully manifested?" he questioned with a playful smile.

The geneticist looked down, abashed, and nervously picking at her overcoat. "Was it that bad?" she timidly wondered, shyly gazing up under her eyelashes to look at Barry, her teeth gnawing on her bottom lip.

He chuckled as he got off the bed and walked up to her, cupping her face delicately in his hands. "You were fine - more than fine!" he admitted with a sincere smile, "You know, before you froze my tongue," he lightly joked.

It was minimal because her body was so cold, but Barry swore he saw the faintest of red hues appear on her cheeks. "I may have gotten a little...excited…" she confessed quietly. "I guess my control slipped…"

"Nothing we can't work on," Barry told her gently, giving her an affectionate wink.

Caitlin rolled her eyes, but he could tell she was truly distressed.

"Cait," he started resolutely, her name weighed with affection, "when I thought I was going to die in that fire, I thought of you," he said, causing the doctor to raise her eyebrows in surprise, her piqued interest egging him to continue, "and it made me realize just how distracted I've been to what's been right in front of me this whole time…you..." he paused, gathering up his courage to continue. "And I'm done with being distracted and wasting my time. I want this," he told her earnestly, trying to overlay each word with a loving intonation. "Do you?"

The speedster watched as she nervously swallowed. "Barry," Caitlin let out worriedly, her voice wobbly. "With these powers...I don't want to hurt you. I - I could never forgive myself," she admitted, their gazes locked, allowing the forensic scientist to see the self-doubt in her eyes.

Barry took her hands into his own, caressing the backs of them with his thumbs. "I know you," he started, looking into her eyes imploringly. "You would never hurt me."

Caitlin opened her mouth to refute, but Barry cut her off.

"Even as Killer Frost, I know you never wanted to hurt me. You stabbed me in the leg and made me slip a few times - you even kissed me," he said, bringing up the first time they kissed, causing his personal physician to dip her head coyly. "But you knew each time that I wouldn't die - you knew I would recover easily. You could have stuck an icicle through my heart, but you didn't, because you couldn't."

Barry pulled Caitlin's hands to his chest so that she could feel his speedy, beating heart.

"I've been battered, bruised and broken more times than I can count," he said to her quietly, watching as she minutely winced, most likely thinking of his worst injuries. "But you were the one that always fixed me - patching me up and looking over me - and I have faith that no matter what persona is talking or what color your hair is, you will not hurt me."

Caitlin looked up at the speedster, a lone tear trickling down her cheek, shaking her head. "I'm broken...and cold..and-"

"Smart and brave and caring and passionate and determined and a million other amazing things," Barry continued, wiping away the tear as it neared her chin before kissing her delicately on the forehead.

She closed her eyes at Barry's sweetness. "But I-"

"Can't sing nor hold your liquor?" Barry finished for her. "I know, but I find those two things about you to be utterly cute," he told her, flashing her a lopsided grin that forced a smile to break out on the woman's face.

Barry mentally patted himself on the bad, enjoying the fact that he got her to genuinely smile. He pulled her to him so that her head was nestled securely under his. "Plus, coldness can be hot as hell," he murmured into her hair, causing the woman in his arms to snort adorably.

"Oh yeah?" she curiously wondered, her fingers tracing the letters on the STAR labs t-shirt he was sporting.

The speedster blew out a hot breath of air. "Ooohh yeah. I mean, have you seen yourself in your Frost outfit? Damnnn!"

Caitlin lightly swatted his torso, her laughter small but reassuring.

Barry smiled to himself, enjoying the sound and wanting to do nothing more than make her happy like that for the foreseeable future. "Cait," he began, her name coming out soft but firm. She tilted her head up to look at him, her eyes showing her vulnerability. "If two people can make this work, it's us. We've always been on the same wavelength - kindred spirits. Even now, my speed can counteract your cold powers - that has to mean something, right?"

Caitlin lowered her eyes, seemingly studying the material of his shirt, deep in thought. "Maybe," she eventually whispered, so quietly he barely heard it himself, but it did ignite a fire of hope within him.

"I believe," Barry said with conviction, causing the doctor to look up at him again. "You should too."

Her eyes looked deeply into his, reading and analyzing them, before slowly nodding her head. "I want this, I do," she said, wrapping her arms around his body, hugging him close. "I'm just afraid," she quietly confessed.

"I know," Barry whispered back, holding her securely as he placed a kiss on the top of her head. He knew that Caitlin would always be afraid that she'd hurt him one day, but no harsh words or frozen tongues would stop him from spending the rest of his life convincing her she wouldn't.

A/N: So this oneshot started when I saw a prompt on tumblr stating that Caitlin freezes Barry's tongue while they're kissing. The prompt was probably supposed to evoke a more comedy approach, but this turned more serious..? I couldn't help it. Sorry! Regardless, I hope you enjoyed reading it. Please let me know what you think! :)