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The Heat Between Us

Summary:

1960s New York. The space race is real, but the Baxter Building is chasing something stranger than orbit.

Dr. Claudia Montrowe is not part of the team, not officially. She's a theoretical physicist with a reputation. She stays out of the spotlight, and she certainly doesn’t have time for Johnny Storm’s charm—or whatever it is he thinks he’s doing. But he keeps showing up anyways.

He jokes. She deflects. He pushes. She pretends not to feel it.

The others treat her like part of the team. Reed counts on her. Sue keeps her close. Ben makes her laugh when no one else can. And Johnny… Johnny won’t stop circling her, no matter how cold she plays it.

The launch is coming, and the rules are shifting. What will Claudia do with Johnny now that she can’t get rid of him.

Notes:

OK, I’ve been ruminating on this fic idea for a very long time.

At first, I was waiting for people to post something but clearly everyone’s itching. So, I’ll do it I guesss. This isn’t a typical slow burn, I feel (although Johnny doesn’t come in until chapter 3. Sorry, babes). This is more escapism, living in the world. So, a warning beforehand, it might seem unnecessarily long, but I like writing descriptions of things so bear with me because I have it planned out and it gets good. Ohhh does it get good. This is very ambitious. This is also my first time writing in a bit so have mercy.

Also, there’s a lot of pseudo intellectualism because I don’t know these things. I’m just a normal person. So, if something is scientifically wonky. Girl get over it. This is fanfiction as hell. But also tell me because I’d love to learn.

I also really wanna post this because as new things are coming out about the fantastic four movie the more things I have to change about my story (that new play-off promo is already fucking up my shit) so let me just get it out there and not have to worry about it too much. Because I don’t know how the movie goes. This will definitely be different from the movie until it comes out then maybe I’ll implement some of the stuff… otherwise enjoy. Pleasee tell me you enjoy it <333

Also, this first chapter is a shorty, so keep that in mind for the future... :)

Chapter 1: First Floor

Chapter Text

Morning — Sublevel One — Revelle Institute, New York City

The elevator shuddered to a halt at Claudia’s destination: Sublevel One, officially. Unofficially, among those who actually worked there, it was known as the real first floor of the Revelle Institute. The Institute had many reputations, depending on who you asked: a prestigious research center, a government-funded ass-kissing factory, a PR palace with a few microscopes, or, if you asked some outspoken individuals, an outright conspiracy. Those impressions weren’t helped by the surface levels, which mostly showcased flashy gadgets and empty spectacle. And yet, for an institution, with such deep government funding, the facilities were almost laughably outdated.

ACCESS KEY REQUIRED

All entries beyond this point demanded personal clearance, a reminder that the real work didn’t happen upstairs. 

Claudia presented her access key. The photo was grainy, grayscale, and unforgiving, like a mugshot taken under duress. Beneath it was a jumble of numbers posing as an ID and a generic job title that bore little resemblance to her actual role. She didn’t mind. It made conversations with her family mercifully brief. 

Click*

WELCOME C. MONTROWE

The entrance lobby tried its best to look hospitable because this was the only sublevel floor with a lobby. A friendly receptionist, a row of cushioned chairs, even a neat spread of semi-relevant magazines. But just beyond that thin layer of comfort, the real tone of Sublevel One set in: walls of bare grey cinderblock, uniform metal doors with no windows, no labels, no indication of what was happening behind them.

“Welcome, Dr. Montrowe,” the receptionist repeated. 

“Hey, Mo,” she replied, without breaking stride. 

She moved past the welcome desk and into the corridor without hesitation. The ID badge clipped to her hip still blinked green from the last scan, an automatic signal to the locks that she belonged here. The hallway, like most of Sublevel One, smelled faintly of mold and old wiring. Overhead lights buzzed in a way that suggested no one had thought to replace them in a decade. Or perhaps the flicker was intentional, an ambient reminder that comfort wasn't the point.

Claudia turned a corner, her footsteps echoing dully on the linoleum. A light orange cart of sealed containers passed her in the opposite direction, wheeled by some young intern who made the mistake of making eye contact. He quickly looked away, as if he’d glanced at something radioactive.

Good instinct.

Most of the people down here didn’t know what anyone else was working on, that was by design. Need-to-know culture wasn't just policy at the Revelle Institute. It was an atmosphere. You learned not to ask. You learned to look like you already understood everything.

B-112 

She stopped at a matte grey door marked only with a code. No nameplate. No placard. Just another question in a building built on answers.

She keyed in her clearance. The door clicked, then slid open with a flat hiss.

Inside was a room that looked more like a war bunker than a lab. It was a circular room with two rows of tables curving to the space of the room. On the left wall, a massive chalkboard filling up the height of the room. Directly in front of the entrance, but on the other side of the room, is a model spacecraft. And to the right of the room were massive computing systems and servers that continuously hummed a soft murmur throughout the room, even while unused. Around the room were other various tools necessary for this project she was assigned to seven months ago. 

Claudia walked to her ‘desk’ (rather half of a table row filled to the brim with files) and hung her coat on the back of the chair before stalking towards the large computers to see if it had finished her calculations of the night before. First, she pulled up the project logs from the night shift. Two of the simulations had stalled again, probably a cooling issue on the B4 processors, which meant she'd have to remind someone, again, that patching software wasn’t a substitute for cleaning physical fans. She marked it with a terse internal note:

B4 SIM #7: throttled. Flagged for manual check. Contact J. Bellara.

A soft knock at the glass, barely audible. Claudia glanced up.

On the left side of the chalkboard, located a small office. Dr. Lindh gave her a cautious half-wave, holding a tablet in one hand and a coffee he’d definitely stolen from the wrong floor in the other. He’d pressed a button to unlock the door, which hissed open slowly. Dr. Corbin Lindh was a man in his mid thirties, with slim glasses, and a blond spikey haircut. Dr. Lindh was a tenured physicist with a biting sense of humor and the mild paranoia of a man who’d been on too many black-budget committees. He often wore a worried grimace that gave him a presumed reputation that he didn’t know what he’s doing. Contrary to belief —  it's just his face.

"Did you see the report from the Denmark substation?" he asked, stepping in.

Claudia didn’t look up from her terminal. "I saw it fail QA three times, if that’s what you mean."

He set the tablet down beside her, lips twitching. “You’re a ray of sunshine, Montrowe.”

She finally glanced over. “Only because this room is windowless.” 

A nod passed between them, before Claudia asked, “Is that the report for our reentry simulations?”

Lindh tapped the tablet, flipping it toward her. “Final run from the overnight batch. Thermal stress thresholds held, but the margin’s narrower than we expected.”

Claudia scanned the summary without touching it, her eyes flicking across the page. “It’s too narrow. Did they factor in lateral drift from attitude correction?”

“They said they did,” Lindh replied, already sounding unconvinced.

“That’s not the same as actually doing it.” She pulled the report onto her primary screen and opened the raw output. Within seconds, she found the missing variables. Sloppy.

She sighed. “They ran this like it was a textbook descent, not a live environment.”

Lindh dragged a hand through his hair. “Should I send it back for revision?”

“No.” She highlighted two sections, adding a comment:

Recalculate with atmospheric variability and off-axis vector adjustment. Reentry is not a straight line.

“We’ll rewrite the model ourselves,” she said. “Theirs is unusable.”

Lindh didn’t argue. He never really did when she used that tone; a decision had been made, and anything else would be a waste of time. He lifted his coffee as if to salute her, then turned to leave.

“Oh, and Lindh,” she added before he reached the door.

He paused.

“Next time, don’t bring me bad news before I’ve warmed up.”

He chuckled under his breath. “Copy that.”

The door hissed shut behind him, and Claudia returned her attention to the dashboard. Already, three new task flags had appeared. Although small fires, all that was needed was a simple extinguishing. No alarms. No credit. Just the kind of invisible labor that kept the Revelle Institute from buckling under the weight of its own ambition. And Claudia, sharp-eyed and under-titled, was the one who kept the project from drifting.

-

It was around noon when Claudia entered the second floor. Currently, she was searching for information from other researchers about spacecraft trials, specifically reentry models. The Revelle Institute’s upper archive was a dead zone for actual discoveries, most of what was kept here was for appearances: glossy project abstracts, polished executive summaries, and enough acronym-heavy documentation to make any real researcher want to chew glass.

Still, some of the old files hadn’t been fully digitized, which meant sifting through physical records: drawers, binders, and occasional stray piles of forgotten research no one had the sense to shred. She moved quietly, methodically, her ID clipped low and her expression unreadable.

A beige folder caught her attention, misfiled by at least three categories and wedged between two unrelated climate studies. The label read:

REENTRY: Variable Shear Correction Trials – R. Richards.

The handwriting on the tab was clean but rushed, like someone had started with discipline and ended in impatience.

She paused.

Richards. As in Reed Richards?

For a second, Claudia just stood there, the folder balanced between her hands, her brow faintly creased. She knew the name, nearly everyone in New York did. The man was practically a myth: the youngest recipient of the Newton Grant, a former Institute Fellow who’d ghosted half a dozen advisory boards before the age of thirty, and someone whose ideas often sounded too theoretical for their own good. And of course he’d have ties to the Revelle. It made a strange kind of sense that this was exactly the sort of place that would indulge a mind like his, brilliant and inconvenient.

She slid it out.

Inside were loose graph papers, simulations printed on recycled data sheets, and equations so dense they looked more like sheet music than aerospace math. Claudia sat down in the nearest chair and began flipping through. 

At first glance, it was a mess. The margins were crowded with scribbled corrections, entire calculations rewritten mid-page. But beneath the chaos was something undeniably compelling: a fresh approach to descent trajectory modeling that she hadn’t seen in any published paper. Ambitious, novel, and just barely executable with modern onboard systems.

But then came the problem.

Claudia’s eyes narrowed. His correction coefficients were all off. Not wildly, not in a way a layperson would catch, but enough to skew the model during the most volatile seconds of reentry. It would drift. Under certain conditions, it could roll unpredictably. In a real practical trial, that could be catastrophic.

She turned the page and found more of the same. Brilliant intuitions, undermined by rushed math. It was like watching someone try to sprint before learning how to walk.

Claudia sat back in her chair; thumb pressed to her lower lip. Reed Richards. Of course it was. A mind big enough to see the edge of the map, though just careless enough to walk straight off it.

She flipped back to the first page and began reworking the equations in her head. The theory wasn’t wrong. It just needed refining.

She hadn’t planned on staying long, but now, it looked like her afternoon was spoken for.

She glanced once over her shoulder. Not many people ever came up here, but because taking someone else’s half-finished work, especially from a misfiled folder in a restricted archive, still technically violated at least three internal access protocols.

Technically.

The second glance wasn’t out of caution; it was out of instinct. There were motion sensors on this floor. Not always active, not always reviewed, but present. And while the archives didn’t have live surveillance, it did have hallway logs, and Claudia knew better than most how long a record could sit dormant before someone bored decided to cross-reference timestamps.

Her fingers hovered over the folder for a beat longer than necessary.

Then again, she wasn’t taking it to publish. She was taking it to fix it.

Claudia slipped the folder beneath the reports she was supposed to be reviewing and stood, adjusting her posture into something blandly official. As she walked, she kept her pace steady, not too fast, not slow enough to raise questions. The overhead lights buzzed faintly as she moved down the corridor, past rows of untouched binders and sealed cabinets. Her badge pinged green at the stairwell checkpoint. She barely breathed until the lock disengaged.

Back in her workspace on Sublevel One, she cleared the far side of her desk, set the folder down, and opened a fresh file on her terminal. She didn’t type right away. She laid out the pages in sequence. First, Richards’ looping script with crossed-out margins and the occasional question mark scrawled in the corner as if he’d grown frustrated of solving his own problems.

Then she began the work of reconstruction. Line by line, she ran his equations through her own logic, translating them into terms that were actually functional and replacing idealized constants with adaptive ranges, accounting for the kinds of stresses that real-world craft would face, not just the theoretical models he'd built in vacuum-sealed labs.

Her projections, already weeks in progress, began to shift.

The Richards model wasn’t just clever; it was potentially revolutionary. Dangerous, yes. The math lacked discipline, and the assumptions leaned too hard on best-case scenarios. But if she could stabilize it, anchor it in actual feedback systems, it could change the entire shape of reentry dynamics. No more brittle descent curves. No more oversized heat shields as compensation for bad planning.

Claudia worked for hours without realizing the time had passed. Somewhere in the background, the lights overhead dimmed slightly, i.e. the building’s subtle way of reminding staff they were staying late.

She didn’t notice. She was already too deep inside someone else’s idea. 

And though she wouldn’t say it out loud, not yet, she was already beginning to imagine the conversation she’d have if she ever met Reed Richards.

Because if she did, she wouldn’t ask him what he meant by the model.

She’d tell him where he went wrong.

At some point, Claudia paused. Not to rest but to recalibrate. Her hand hovered over the terminal, ready to input another correction, when she caught it.

A flicker.

Not on the screen, but in her periphery. A slight, unmistakable delay in the data refresh window. Just half a second too long. Most wouldn’t notice. But she did. She checked the packet logs. Nothing flagged.

Still.

She saved a duplicate of her work locally, encrypted the folder, and scrubbed her recent activity under a nondescript task code. It wasn’t paranoia. It was protocol. And anyway, she told herself, it was probably just a system hiccup. Revelle’s backend was older than some of its interns.

Still, as she sat back in her chair and stared at the line of equations slowly converging into something elegant, the thought persisted:

Someone else could be watching.

-

Claudia arrived the next morning at 07:42. A few minutes earlier than usual, but not enough to draw attention. She liked to blend in, to be consistent without being noticeable.

ACCESS KEY REQUIRED

Click*

WELCOME C. MONTROWE

“Welcome, Dr. Montrowe,” the receptionist repeated. 

“Hey, Mo,” she replied. 

Sublevel One was still quiet, the lights running on motion sensors, kicking on only as she passed. 

She entered her lab, keyed the door behind her, and powered on the system. Her station greeted her with the same sterile prompt as always. No alerts. No flagged messages. No follow-up about the folder she hadn’t technically checked out.

Good.

The revisions had grown more complicated toward the end; less about correcting basic math and more about stabilizing Reed’s theoretical model under edge-case scenarios. Emergency spinouts. Irregular solar flare interference. Upper-atmosphere wind shear. The model was brilliant. Still raw. But now, nearly operable. She caught herself almost impressed.

As she annotated the last page from yesterday’s session, she paused and reached for her mug. Cold. She hadn’t remembered pouring it.

That was fine. She didn’t need warmth. She needed focus.

“I passed that over to you an hour ago.”

A voice washed over her that felt like a bucket of cold water. “Dr. Lindh. When did you get in?”

He was standing just outside the threshold of her workspace, coffee in hand, eyes sharp behind his smudged glasses. He wasn’t the sort to sneak up on people, not intentionally, but he had a quietness about him that occasionally triggered Claudia’s fight-or-flight. “About the same time you did,” he said casually, leaning on the doorframe. “Figured you’d already seen the updates, but you’ve been locked in with that file since you sat down.”

Claudia turned slightly in her chair, just enough to obscure the corner of her screen. “I was wrapping up something from yesterday.”

He took a sip from his mug, watching her the way some people watched chess boards. “Same ‘something’ you weren’t supposed to be working on?”

Her spine stayed straight, eyes neutral. “I’m not sure I follow.”

“I ran a sync check on the local simulation node.” Lindh’s voice didn’t rise, didn’t accuse. “Saw a phantom task running overnight. You’re the only one who doesn’t rename her temp files.”

Claudia was silent for half a beat too long.

“Relax,” he added, pushing off the frame. “I’m not going to report you. I just want to know what it is that’s worth risking a clearance strike for.”

She hesitated, then pulled up the revised model on the main screen. Lines of code, plotted descent arcs, corrected coefficients. She didn’t explain it, she let the work speak for itself.

Lindh stepped closer, squinting slightly. His eyebrows lifted before he even finished reading. “This is... Richards’ framework.”

She nodded once.

“This is not Richards’ math.”

“Not anymore,” she said.

He stared at the model for another few seconds, then let out a low whistle.

“You rebuilt it.”

“I refined it,” she corrected. “It was promising, but unstable. Too many assumptions. Too much faith in the idea, not enough grounding in practical input.”

“Well, that’s not exactly news. The man’s a miracle engine. He’s bound to blow a few gaskets.”

“He assumed symmetry under collapse. The system doesn’t freeze at terminal convergence. It splinters. Not into chaos, but into mirrored recursion loops. Like a standing wave in a broken chamber.”

Lindh looked at her, something unreadable flickering behind his eyes. “You know if someone catches wind of this—”

“They won’t,” she said flatly.

“Claudia…”

“I’m not publishing it. I’m not claiming it. I’m fixing it.” She paused, then added, quieter, “Because no one else did.”

For a moment, he didn’t say anything. Then he reached into his coat pocket, pulled out a small, wrapped granola bar, and set it on her desk.

“If you’re going to break rules,” he said, “at least eat something while you do it.”

He left without another word.

-

Two Weeks Later

The presentation room on Sublevel Four wasn’t particularly pleasant. The air ran a few degrees too cold. The chairs were regulation-issue: stiff-backed, thinly padded, designed more for compliance than collaboration. There was no clock on the wall — intentional, probably. Just blank grey paneling, a projector screen with a slight flicker at the edges, and two discrete ceiling-mounted cameras that tracked movement whether you liked it or not. The lights overhead buzzed faintly in intervals. The kind of room that made even good news feel bad. But it was the designated board-level briefing space. Today, Claudia was presenting findings that had, unofficially, made ripples through at least three departments.

She stood at the front of the room, her hands steady, her blazer perfectly pressed, her face composed with the kind of quiet control that suggested she’d slept well, in truth she hadn’t. Beneath the surface, her nerves flickered like static, but none of it reached her expression. Dr. Claudia Montrowe didn’t fidget. She paced her breathing, timed her words. Every step leading to this moment had been deliberate.

It was a dark room where board members were arranged in a shallow arc along a long continuous curving table facing her. There were many empty seats, only housing necessary individuals. Some skimmed their printed agendas; others squinted at her slides, trying to decide whether this was worth their attention. Dr. Emerick, head of Aerospace Systems, sat directly in the center, elbow on the armrest, fingering his temples like he was measuring her sentence by sentence. Beside him was Director Hahn, a chronic pen-clicker with a suspicious streak and a tendency to interrupt mid-sentence. The rest Claudia had studied in advance.

And just off to the right corner, seated in the second row, just behind the board table, with the status of an invited guest, was Dr. Lindh. He didn’t wear a suit. He never did. Today he’d opted for his usual black turtleneck under a faded taupe blazer, the collar slightly uneven, like he’d dressed in a hurry. He wasn’t looking at her slide, no, he was watching her. And though his expression was neutral, he gave her a small, almost imperceptible nod as she adjusted the clicker in her hand. The kind of gesture that said: You’ve got this. Don’t look back.

Claudia didn’t.

Behind her, the screen flickered faintly. Her calculations. Her corrections layered cleanly over the bones of a framework that, two weeks ago, had been buried in an unmarked folder, mislabeled and forgotten.

Now it was the centerpiece of a closed-door presentation with top-level clearance.

Dynamic Descent Modeling — Preliminary Integration Trials.

She raised the pointer.

“Good morning. I’ll begin with a breakdown of the reentry conditions modeled under the new dynamic descent protocol.”

And just like that, the room shifted; pens poised, brows furrowed, silence folding in tight around her words. The audience wasn’t large, but it mattered.

“This model integrates live-response correction during reentry events, including unpredictable variables such as, atmospheric turbulence, onboard inertia drift, and solar interference events,” she explained, the laser pointer gliding cleanly across the screen. “Our composite algorithm reduces fatal deviation margin by 42 percent compared to current gold-standard parameters.”

A few of the directors exchanged glances. Someone scribbled a note. Another nodded, half-impressed, half-still-trying-to-understand.

Claudia continued, calm, precise.

She didn’t see him at first.

Not until she shifted to the next slide, the core correction equation. The one she’d rebuilt from scratch. The one that had started as someone else’s half-finished thought. 

She glanced toward the back of the room. Second row. Left side.

Reed Richards.

He hadn’t been listed on the attendance docket. Probably last-minute. Possibly invited by one of the quieter directors for commentary. But there he was, posture relaxed but eyes fixed on the screen with an intensity that cracked his otherwise neutral expression.

Claudia didn’t flinch. She didn’t pause or stutter or acknowledge him in any way.

But she saw the way his jaw flexed. The flicker of tension at his temple. The fact that his pen, which had been tapping slowly against his knee, stopped completely when she moved to the validation slides.

He recognized it.

Of course he did.

This was his framework, but rewritten, made viable. But the shape of the original idea was still buried in the structure like a watermark.

She went on.

“This model has been tested across 1,200 reentry simulations, with a 94 percent stabilization rate. I’ve attached projections for onboard implementation protocols, as well as failure mode thresholds for next-stage testing.”

A director leaned forward. “You ran these simulations alone?”

Claudia nodded. “Initial drafts were supported by archived frameworks. Rewritten internally.”

Another director turned. “Dr. Richards, you’ve worked in descent modeling before. Any thoughts?”

For half a second, Reed looked like someone had pulled the floor out from under him. But his face recovered fast. He smiled, slightly. “The model’s impressive. It’s an elegant approach. I’d be curious to see her variable suppression algorithm in long-term prediction ranges, but… yes. It tracks.”

“And the archived framework she referenced?”

Reed shrugged just enough to sell it. “Could’ve been one of a hundred from the last decade. Half the Institute’s dusty subdirectories are full of that stuff.”

A few chuckles.

The moment passed.

But Claudia saw the tightness behind his eyes and neck. The calculation. The recognition that something he’d buried had resurfaced but better and no longer his alone.

She clicked to the final slide. “Pending clearance, the model is ready for Phase II development.”

The room gave a polite round of approval.

She nodded, stepped back, and let the screen fade to black.

The moment the meeting ended, the usual rustle of chairs and shuffling of papers began, low and procedural. Directors offered polite nods to one another, a few mutterings of something about follow-up schedules and external clearances. The screen behind Claudia blinked off.

But Reed Richards didn’t speak.

He stood, not hastily, but with a movement that signaled no interest in lingering. His face remained neutral, unreadable to everyone else in the room. But Claudia saw it: he was avoiding her. Quickly shaking hands with a few attendees, Reed made a scan of the board before exiting without so much as a glance in her direction.

Gone.

Out the door, down the hall, no parting comment. Not even a nod.

Claudia’s mouth felt dry. She tucked the pointer into her folder slowly, carefully. Too carefully. Her fingers felt stiff. Behind her, someone muttered something complimentary about the model. Another director mentioned follow-up testing. It was the kind of benign post-briefing chatter that usually meant things had gone well. But her focus stayed locked on the door Reed had disappeared through. She felt Dr. Lindh come up beside her. “He didn’t say a word,” she murmured.

“I noticed,” he said under his breath, handing her a tablet she didn’t need. “Too pleasant. For him.”

“You think he’s going to flag it?”

“I think,” Lindh said carefully, “he didn’t expect to see his work reflected back at him without warning. Especially not like that … neat, functional, and presented by someone else.”

Claudia kept her expression still, but her jaw ached. She hadn’t taken credit. She hadn’t claimed authorship of the framework. But she hadn’t cited it either. And now, for the first time since she’d opened that dusty folder, she wasn’t sure if she’d made the right call.

Lindh lowered his voice further. “If he wanted to blow it up, he would’ve done it in the room. That’s his style. You saw how fast he left. That was... meaningful.”

“Which means?”

“Which means he’s either letting it go… or thinking very hard about what to do next.”

Claudia exhaled, slow and shallow. “Wonderful.”

They walked out together. The hallway lights buzzed softly overhead, the hum of fluorescent fixtures somehow louder in the wake of Reed’s silence. The model was good. The math was sound. The presentation was a success. And yet, for the first time in weeks, Claudia felt like she might have stepped into something she couldn’t control.