Chapter Text
The smoke is curling thickly as they rush down the hallway, walls blistered with heat and beams groaning overhead. Eddie pushes forward, radio pressed to his shoulder, Chimney’s voice crackling in and out through static and distance.
“Teenage son might still be upstairs,” Chimney had said, the homeowner sobbing at his side.
Buck is leading the way a few steps ahead of Eddie, crouched low and axe in hand, his silhouette flickering in the stuttering glow and smoke of the flames.
“Second door on the left,” Eddie calls, voice muffled behind the mask. He’s already sweating under the turnout gear, every inch of his body tense.
They reach the door, and Buck’s already bracing for action. One shoulder hits. Then another. It gives on his second try, slamming open with a hollow bang against the wall.
“Kid?” Buck calls out, stepping inside, head whipping around with frantic urgency.
Eddie follows, faltering in his steps as he takes in the scene before him.
It’s a bedroom, caught mid-transformation. There’s flames licking at the bedframe, sheets smoldering at the edges, smoke curling up the walls like fingers looking for a grip. The fire hasn’t taken it all yet, but it’s starting to. But the far corner?
Untouched.
Not just less burned, but untouched. There’s no smoke, no soot, not even a lick of fire. Like the flames were actively trying to skip it. And standing there, impossibly pristine, is a mirror.
It’s tall. Antique. The kind with ornate brass framing and a warped-glass surface, more decorative than useful. Eddie barely registers it beyond thinking that’s weird before Buck starts moving toward it.
“Buck,” Eddie says, voice sharp.
Buck pauses mid-step. Turns slightly, just enough to let Eddie see his profile. Like he heard him but isn’t quite there.
“I see him,” Buck murmurs, voice nearly lost to the crackling fire around them.
Eddie frowns. “What?”
“There. In the mirror.”
Eddie steps up beside him, scanning the room. There’s no one. Nobody. No sign of the kid. But in the mirror, yeah. A flicker of movement.
Not a reflection. Not quite. Just the suggestion of a shape. Something standing behind them. Wrong-sized. Elongated.
Eddie turns on instinct. Except when he does, there’s nothing there. Just fire and smoke.
He looks back. The mirror’s empty. Just the two of them now. And Buck’s staring at it like he can’t look away. Transfixed on his own reflection.
“Come on,” Eddie says, reaching for his arm. “Let’s clear the rest of the floor.”
Buck doesn’t move. Just lifts a hand and brushes his fingertips across the surface of the glass.
The mirror ripples. Just the faintest shimmer, like the air over a stovetop. A blink-and-you-miss-it thing.
Eddie’s breath catches. “Buck.”
Buck jerks back like waking from a dream. Blinks rapidly, then turns to Eddie with a puzzled smile. “What?”
“You okay?”
“Yeah,” Buck says, like it’s obvious. His gaze drifts around the room. “Where’s the kid?”
“There is no kid,” Eddie says slowly. “At least... not here.”
Buck nods. Too fast. “Right. Yeah.”
Eddie glances at the mirror one last time before they rush back out of the room.
The firehouse is quieter than usual when they get back.
He tells himself it’s just post-call nerves. That kind of fire always shakes something loose in people. For Eddie, it hovers with the type of heat that makes him feel like he’s back in that Humvee, ribs grinding against armour, radio screaming.
But it’s not just that.
Buck hasn’t said a word since they loaded into the engine. He didn’t crack a joke. Didn’t complain about the smoke or his shoulder or the fact that his hair smells like a fireplace. He just sat there, staring out the window, jaw locked like it’s taking effort to keep it closed.
He’s probably worried about the kid, Eddie thinks. The one they didn’t find. No body under the desk, no sign of him tucked into the closet. Maybe he got out. Maybe. But if he didn’t…
If he didn’t, then the only people left to blame are Buck and Eddie.
Did we even check under the bed?
Eddie pushes the thought down. Hard. Follows the soft hiss of the locker room showers instead. Buck’s already there, moving through the motions of unstrapping his gear as wet fabric slaps dully against the tiled floors. Each movement is lagging behind the last, like he’s copying from muscle memory that’s not quite his.
Buck doesn’t even seem to notice him enter. Eddie’s gut twists, and he forces his gaze away, feeling like he’s intruding on something private, something he isn’t meant to see. He breathes in through his nose, grounding himself in the steam-heavy air, and heads for one of the cubicles instead of the open showers, giving Buck some space. Some privacy.
His movement seems to have caught Buck’s attention, because he catches the subtle tilt of Buck’s head right before he turns, the way Buck tracks his movement, and his gaze lingering until Eddie shuts the cubicle door behind him. It’s enough to raise the hair on Eddie’s arms despite the humid air.
By the time Eddie finishes, towel slung low around his waist, Buck’s standing at the sinks. Staring at himself in the mirror.
Water still clings to his skin, beading and sliding down the slope of his back. His hair’s wet, curling into his neck. It doesn’t look like he even tried to dry off.
Eddie hesitates, towel half-forgotten in his hand.
“Buck,” he says finally, breaking what feels like a decade of silence.
Buck turns his head, but not all the way. Just enough to acknowledge Eddie’s presence with the corner of his eye.
“Yeah?”
“You doing okay, man?”
Buck blinks, slow and almost mechanical. Then, a beat too late, he turns fully and smiles.
The smile is wrong. Not enough to be obvious, but enough. A fraction too delayed. The corners too tight. The eyes not quite reaching it.
“Yeah,” Buck says. “Just tired.”
Eddie watches him carefully. There’s something missing behind his eyes. Not emptiness exactly, but something worse. A displacement. Like a picture shifted in its frame.
He tells himself it’s normal. It’s been a long time since they had a call like that, a kid they couldn’t find. Some calls hit harder than others. It happens.
Still, the feeling gnaws at him.
He pushes through it, forces a smile of his own. “Mirror got you spooked?” he asks, meaning it half as a joke, half as a feeler.
Buck’s smile doesn’t waver. If anything, it freezes slightly more in place. “What mirror?”
Eddie stills. “In the house,” he says slowly, carefully. “In the bedroom. You touched it.”
“There was a mirror?” Buck frowns, brow knitting tight. He says it like he’s trying to piece together someone else’s dream. Distant. Faintly confused.
“Yeah,” Eddie says, pulse kicking up. “You said you saw the kid in it.”
Buck blinks again, slower this time, like dragging himself through syrup. Then his face softens, guilt flashing across his features.
“Oh, right. Yeah. The kid. Sorry, my mind’s just... a mess,” Buck says, rubbing at the back of his neck.
He looks embarrassed, maybe even ashamed. Like a rookie caught zoning out. Eddie watches him for a moment longer, weighing the unease twisting in his gut.
Maybe it’s the truth. Maybe it really is just the call. They all have days like this. Some calls break through the armour easier than others.
No one’s immune to it.
They get a call soon after, and the firehouse kicks back into full swing, the previous emergency slipping into the background as muscle memory takes over. That’s how you survive this job; you stay sharp because even a moment’s distraction could cost someone their life.
Buck’s back to his usual self now, making quick jokes with Hen, carrying his gear like it's second nature and sliding into the truck with that familiar energy.
But Eddie’s eyes keep drifting to him. Half concern, half worry, and half something else he doesn’t quite know yet.
They pull up to a car accident, glass glittering on the asphalt under harsh emergency lights. Bobby barks out orders, Hen and Chim move like a unit to triage the victims, and Buck heads straight for the crumpled driver’s side, already pulling his gloves on. Everything’s business as usual. Fast. Efficient.
But then,
Buck’s hand hovers just a second too long over the door handle. Like he’s thinking about it. Thinking about what to do next. Like there’s a second of hesitation that doesn’t belong.
And when he turns to Eddie, his smile is... off. Too wide. Too perfect. The kind of smile you practice in a mirror when you’re trying to look normal. Eddie feels a cold wave of unease.
“You good, Diaz?” Buck asks, stepping closer, voice light and too casual. Like he’s trying to make sure Eddie’s okay. Like he already knows Eddie isn’t.
Eddie blinks, caught a little off guard. His heart hammers in his chest for no good reason. It's Buck. It’s just Buck.
“Yeah,” he says, clearing his throat. “Let’s just get this over with.”
There’s a flicker in Buck’s eyes. Quick. Sharp. Gone before Eddie can catch it. But he feels it, like a static charge brushing over his skin.
“Right,” Buck says, snapping his gloves into place. “Let’s do it.”
The tension between them is thick enough to choke on, heavy in a way Eddie can’t explain. Like standing at the edge of something he can’t see.
Something’s off today. Eddie doesn’t know exactly what, but it’s there, curling in the pit of his stomach. He tells himself it’s just exhaustion – the tail-end of a brutal shift, too many calls stacked too close together. His body’s running on fumes. His brain's probably making ghosts out of smoke.
That has to be it.
Because on the surface, Buck's acting exactly like he should – laughing at Hen’s jokes, trading wisecracks with Chimney, tossing Bobby a playful salute. Perfectly normal.
It almost convinces Eddie he’s overthinking it. Almost.
Hours later, they’re sprawled around the loft, decompressing. Phones out, scrolling aimlessly. The scent of tomato sauce and something buttery is curling through the air credits to Bobby and Chimney at the stove, with the latter pretending to be auditioning for MasterChef.
Hen’s at the counter, sipping coffee and scrolling through her tablet. Buck’s at the kitchen table, feet kicked up, grinning at something Bobby said.
Normal. Fine.
Until Eddie hears Buck teasing Chimney about something dumb, probably one of their endless inside jokes, but the words taper off weirdly at the end. The rhythm’s wrong. The laugh that follows is a beat too late, a hair too soft.
Eddie’s gaze flickers to him without thinking. Watches the way Buck’s smile strains just a little, the way he blinks like he’s steadying himself between words. It’s small. Barely anything. But Eddie notices.
He looks away, telling himself he’s imagining it. Telling himself he’s tired, stretched thin, hyper-fixating on nothing. He shoots one last text to his group chat with Chris and Carla, and pockets his phone, joining the rest of them in the kitchen.
Eddie slides into his usual seat. Buck tosses him a grin, easy and bright, and holds out a mug already filled the way Eddie likes it: black, a splash of milk. It’s automatic. Familiar.
Eddie takes it, their fingers brushing for just a second too long. He pulls back quickly, but Buck’s smile stays warm.
And then Eddie notices. Buck’s holding the mug with his left hand.
He always uses his right. Even when his shoulder was busted last year, he stubbornly favoured it, saying the weight felt more natural that way.
It's nothing. It's probably nothing.
“Thanks,” Eddie says, forcing a grin that he hopes reaches his eyes.
Buck’s eyes linger on him a little longer than normal, just a beat too long. Then he nods, almost like he's trying to remember something. "Of course," he says, with that easy confidence that feels too calculated. Too smooth.
Eddie feels his stomach twist.
Bobby hands out plates, and they dig in. Everyone’s talking over each other, teasing Chim about the overcooked chicken and complimenting Bobby for his pasta. Buck’s bantering back with ease, smirking at Bobby’s dad jokes, rolling his eyes when Hen roasts his haircut.
Eddie watches him the whole time.
Buck's got the rhythm down perfectly – the timing, the expressions, the casual shoulder nudges. But it’s like listening to a song with one note slightly out of tune. You don’t catch it at first, but once you hear it, you can't unhear it.
He's mimicking Buck.
No. That’s stupid. That’s crazy.
“Eddie,” Buck cuts into his spiralling, pointing his fork at him like it’s part of the conversation, “how about I take Chris to the arcade during your session with Frank this week?”
Eddie blinks, something crawling up his chest. He shifts in his seat. It's not exactly public knowledge that he stopped going, but he also hadn't mentioned Frank in months, so everyone just assumed he’d stopped anyway. “I haven’t seen Frank in a while,” he says carefully.
“Oh,” Buck says, and laughs, like it’s a shared joke. “Man, time’s fake. Could’ve sworn it was more recent.”
Bobby pulls out his phone, disrupting the creeping tension. “Check out this photo Athena sent me. Brisket in that weird sun hat.”
Buck leans in, laughing. "Oh, that's adorable. How old is he now?"
Everyone’s laughing, focused on the picture, but Eddie freezes.
Because Buck knows Brisket. He was there when they adopted him. He held the leash. He bought him a steak-shaped toy. He brings treats every time he visits. Buck knows that dog like family.
And yet he asks the question like he doesn't.
Eddie keeps eating. Keeps watching.
After lunch, Eddie props his phone against his thermos and calls Christopher on FaceTime. It's shaping up to be a slow evening, the kind that stretches too long, which is exactly why Buck perks up from where he’s sprawled on the couch, hearing Christopher’s voice echo too loud in the quiet loft.
“Hey, Chris,” Buck says, pulling up a chair next to Eddie. “You still working on that mural project?”
Chris frowns. “That was last semester.”
Buck pauses, only for a beat. “Right. I meant the poetry one.”
Eddie glances over, something cold slipping down his spine.
Because no. Buck hated the poetry unit. Groaned about how hard it was to help Chris come up with metaphors. Teased Eddie for being “weirdly good at that stuff.” He’d called it their “mutual suffering arc.”
But now he’s acting like it’s just another update.
Chris doesn’t seem to notice. He shrugs. “It’s kind of boring. I’m doing a book report now.”
“Nice,” Buck says. “What book?”
Chris holds it up to the screen: The Martian. The corners are dog-eared and there's a sticky note peeking out.
Buck grins. “Love that one. The potato scene’s the best.”
And yeah. Buck’s probably read it. Probably seen the movie. He could be telling the truth.
But Eddie remembers something else.
Buck stayed up late rereading Hatchet because Chris was struggling to connect with it. He muttered, “Why is this kid just eating berries and thinking about planes?” and Chris laughed so hard he he almost fell off the couch.
That was the book he’d planned to do the report on. They’d talked about it last week. Hell, it was still on their kitchen table two days ago.
Eddie clears his throat. “Didn’t you just start Hatchet, mijo?”
Chris looks confused for a second, then nods. “Yeah, but I switched. I like this one better.”
“Oh,” Buck says. And again, it’s just a little too smooth. “Cool.”
Eddie doesn’t say anything, but his fingers tighten on the handle of his mug, because Buck should’ve known that. Because Buck never forgets what Chris is reading.
The call ends a few minutes later, Chris waving goodbye. Eddie pockets his phone, mind still racing from Buck’s behaviour, when he sees it.
Buck. Watching him.
Not smiling, not teasing. Just watching. Blank-faced. Studying.
Eddie’s heart stutters. His hand tightens instinctively around his phone.
Buck blinks, and just like that, the moment’s gone. A wide, easy grin spreads across his face. He jabs a finger toward Eddie. “You got a smudge on your cheek.”
Eddie forces a huff of a laugh, wiping at his cheek automatically even though he knows there’s nothing there.
Buck’s already leaning back in his chair, casual, relaxed, like nothing happened at all. But Eddie can't unsee it. Can't unfeel the chill working its way into his bones.
There’s something wrong. Something very wrong. And Buck’s smile, so bright and effortless, feels like the biggest anomaly of all.
It’s only much later, at the end of the shift, when Buck moves to grab his jacket, heading out of the locker room with his usual energetic pace, that Eddie notices the next thing.
Buck pulls the jacket on with his left arm first. The arm that isn’t his dominant one.
It’s another strange, tiny thing, but it’s enough to lodge itself in Eddie’s mind like a thorn. Buck never does that. He always puts his right arm in first. Always leads with the shoulder he trusts, the one he can move without thinking.
Eddie’s breath catches, but he doesn’t move. Not yet.
"Got a date with a hot dog stand," Buck jokes, spinning on the balls of his feet, grinning. He’s already back to the Buck Eddie knows. Too much like the Buck that Eddie knows. "You coming, Eddie?"
Eddie looks up, his eyes narrowing just slightly.
"I’ll pass," he says, forcing the words to sound normal. "Carla’s waiting on me. Don’t think hot dogs are a good enough excuse to be late."
Buck chuckles, like it’s nothing, like it’s just normal. Like everything that’s been bothering Eddie isn’t there at all.
“Yeah, fair,” Buck nods. “Well, send Carla my regards! See ya,” Buck calls over his shoulder as he leaves.
Eddie’s hands are still gripping his t-shirt, hard enough to form creases, as he watches Buck go. His heart beats in his ears, quick and messy. Buck doesn’t wait like he usually does, and Eddie doesn’t follow Buck out like he usually does, shoulders bumping into each other all the way to their cars.
Everything’s fine.
But it isn’t. It isn’t fine. He knows it’s not fine, but he doesn’t know why. And it’s gnawing at him in a way that makes him want to tear the whole damn place down to look for answers.
But he doesn’t.
It’s not like he can say anything. Not without looking insane.
As days pass, the shift in Buck’s behaviour is like a thread slowly unraveling.
It’s the way he ties his boots in the morning. Left foot first. Not his usual right. Buck’s always been right-handed. He always leads with his right foot. The thought clings to Eddie like static.
Eddie’s watching from outside the glass walls of their locker room, half-hiding behind a pillar, but Buck doesn’t notice. He never does anymore, which is bizarre by itself.
“Hey, you okay?” Chimney’s voice cuts through his thoughts.
Eddie blinks, shaking himself back into the present. “Yeah. Just... you ever get the feeling like something’s off?”
Chimney raises an eyebrow. “You’re not getting superstitious on us now, are you?”
Eddie half-smiles, but it doesn’t reach his eyes. “No. I’m just... tired, I guess.”
But as Chimney moves on, heading toward the locker room, Eddie’s gaze returns to Buck.
He’s still doing it. Still mirroring the right-to-left shift. Still too perfect in his behaviour, too practiced, like every motion has been rehearsed.
He does it again, when they’re going through truck equipment checks, and Buck’s holding the pen in his left hand – wrong – and the clipboard on his right. Wrong.
It’s nothing obvious. Nothing you could point to and say, See? That’s not him. No smoking gun. No missing memory, per se. Buck walks into the firehouse like he always does – shoulders back, smile easy, joking with Hen, handing Chimney a coffee like muscle memory.
But Eddie knows.
He’s standing in the kitchen, holding his mug too tightly. Watching.
The way Buck walks two steps behind Bobby instead of beside him. The way he doesn’t greet Christopher with his usual, excited Hey buddy!, instead with just a wave and a smile, or a casual Hey, Chris!
The way his laugh hits a half-second too late.
“You good, Eddie?” Hen asks, nudging him. “You look like you’ve seen a ghost.”
Eddie’s jaw twitches. He doesn’t answer. He doesn’t exactly know what he’s seeing.
Later, in the locker room, Buck strips off his turnout and says, “You still using that blue school bag for Chris? The one with the frayed strap?”
Eddie freezes.
Because that bag was misplaced at the zoo last year. And Buck had never liked it – said it was falling apart. He got Chris a new one himself. It’s in Chris’ room, which Buck saw himself two nights ago.
“That’s not the one he uses,” Eddie says slowly, heat already sparking in his chest.
Buck blinks. Too slow.
“Oh,” he says. “Right. Forgot.”
The world narrows to a pinprick.
With a sharp, furious motion, Eddie slams his locker shut, the metallic crack echoing through the room like a gunshot. The sound makes Buck flinch, barely, but Eddie sees it.
He pins Buck – this Buck, this stranger wearing Buck’s face – with a stare like a blade.
“What did you say to me the night of the blackout?” Eddie asks, voice low and lethal.
A flicker of something passes over Buck’s face. Confusion. Surprise. Panic?
He recovers too fast.
“I said a lot of things,” Buck replies. “You’ll have to be more specific.”
He steps forward, slow and unrelenting, until they’re chest to chest, until there’s nowhere for Buck to look but at him. Fire between his teeth, rage in his blood.
“No,” he says, voice low, measured, deadly. “You said, ‘I’d stay with you even if you asked me not to.’ And I said— What did I say, Buck?”
Buck says nothing.
Eddie's fists clench, and the last of his restraint snaps cleanly in two.
“Get the hell away from me,” he growls.