The common room is unusually quiet for a sunny afternoon.

Light pours in through the tall windows, warm and lazy, dust motes drifting in the air. Someone left a record playing low—old rock, faint crackle. Tony’s on one couch half-arguing with Bruce about something technical, Pepper perched beside him with a tablet. Sam and Steve are mid-conversation near the kitchen.

And Bucky is leaning against the far wall, arms crossed, metal hand catching the sun.

He’s watching her. He always is.

Not in a way that draws attention—just a steady awareness, the same way he tracks exits or counts people in a room. She’s sitting cross-legged on the floor near the coffee table, relaxed, smiling at something Steve says. She looks… normal. Safe. Like nothing in the world could hurt her right now.

The sunlight shifts.

It glances off the windows, refracts—and suddenly flares hard against the chrome of Bucky’s arm.

A sharp, stuttering flash.

Bucky barely has time to register it before she stiffens.

Her smile falters. Her head tilts, just slightly, like she’s listening to something no one else can hear. Then she goes rigid, hands curling inward as her body betrays her.

“Hey—?” Steve starts.

Pepper is already moving. “Tony.”

Tony’s on his feet in an instant. “FRIDAY—scan her. Heart rate, temperature, now!”

The room snaps into motion.

Pepper drops to the floor beside her, guiding her gently, efficiently, keeping her head from striking the table as her body begins to seize. Tony’s voice is sharp but controlled, all fear tucked under command as holograms flare to life around them.

Bucky doesn’t move.

Not because he doesn’t want to—but because his brain has stalled, frozen on one terrible, looping thought.

I did this.

The light. His arm. The way she’d been sitting right there.

He’s seen seizures before—in old war footage, in Hydra facilities—but this is different. This is her. The one who sits with him when nightmares tear him out of sleep. The one who never flinches at his scars. The one who meets his eyes like she isn’t afraid of what’s in them.

No one told him.

No one warned him.

“Epilepsy,” Pepper says calmly, grounding, like this isn’t the first time she’s said the word. “She’s had it since she was little. She’s okay. Just—give her space.”

Epilepsy.

The word hits Bucky like a punch to the chest.

His jaw tightens. His metal fingers curl, reflexive, the arm suddenly feeling less like a shield and more like a weapon. He takes a step back, then another, pressing himself into the shadows like he’s afraid the light will touch him again.

I hurt her.

Tony glances up, eyes flicking to Bucky—not accusing, not angry. Just aware. “It’s not your fault,” he snaps automatically, like he knows exactly where Bucky’s mind just went.

But Bucky isn’t listening.

All he can see is her on the floor, the room orbiting around her, and the terrifying realization that there are parts of her life—parts of her fragility—that he didn’t know.

And that scares him more than any nightmare ever has.