She had watched him go under.
He hadn't come back up.
It was the drugs. Natasha had seen them administered, watched the doctor inject him. He'd succumbed to sleep, but not before asking her something. Something that changed her.
"If.. If I'd asked you to marry me, would you have said yes?"
She'd told him yes, and he'd smiled hugely as he closed his eyes.
A day later, she'd gone back to see him.
The same doctor as before had come up to her, his eyes sombre. He told her that something had gone wrong, and Clint hadn't woken up.
She doesn't remember much of what happened. In a trance, she'd swung her arm at the doctor, who went down. She'd shouted obscenities in Russian at the hospital staff as security restrained her.
She comes back the next day and demands quietly but firmly to see him.
They let her in reluctantly, warning her to be careful.
She walks in, feeling oddly light, as though her body knew that it would take much to push her over the edge. As though her brain knew how unstable she was, and warned the rest of the body to tread carefully.
She walks in, and she stops.
He looks so small.
She's scared of how vulnerable he appears. This isn't her partner. This isn't the man who joked with her, or held her when she cried (and she only ever cried in front of him). This isn't the man whose eyes blazed with fire in the rage of war.
This isn't Clint Barton.
But it is. And she's scared of him.
I did this, she thinks, and a surge of something worse than guilt courses through her. My bullet. Aimed for me. My fault. My fault.
Clint's breaths are shallow.
She sits there all day, looking at him. Vulnerable, small... But more peaceful than she's seen him in a long time. Heaven knows he needed the sleep. Maybe that's the only reason he hasn't woken up yet. Maybe he's just asleep. That's what she tells herself to stop the overwhelming guilt from drowning her.
Night falls, and the hospital staff enter. They have to drag her out as she sobs and screams protests at them. She begs and she pleads, she threatens and she bargains, but still they drag her out and she breaks down into tears as they pull her out the door.
She comes back the next day, and every day after that.
Fury tries to reason with her, but she swears at him and stalks back to the hospital. None of the other Avengers can touch her or even talk to her without her turning and hissing at them.
She knows they don't understand why she's so unhappy. But she does, clear as day. She knows it's not just because she loves him, although she does. But Natasha Romanoff is cold and calculating. She can handle a loss, even a great one. Or at least, she can hide it.
But this one is her own fault.
She despises herself.
It's her fault, she tells herself. Her fault that the man she loves lies motionless.
She goes back to the hospital for the fifth day in a row.
He still hasn't stirred.
She stays again. All day. Just sitting. Not talking, not touching. Just looking at him.
A tear slips down her cheek.
Night falls again, and she prepares to be talked out of the room.
A doctor comes in. The one she punched out.
"You can stay tonight," he says quietly.
"Just let me stay for another minute- What?"
He smiles, a small smile. "You can stay tonight. We trust you."
She looks startled, but manages a smile back. A genuine one. "Thank you," she says, and means it. "I'm sorry for hitting you," she adds. "You didn't deserve that."
He shrugs. "Don't sweat it." He nods at her and leaves, and she sees the lights go off outside of the room.
She looks at Clint. "Hear that, Clint? You're- You're stuck with me tonight."
He doesn't say anything, of course. She thinks he's improved. He looks stronger, more like he's simply asleep rather than... Well, he looks better.
She hesitates. Slowly, she lifts up one corner of the blanket and slides in. She cuddles up to him and mumbles, "G'night, Clint..." And she falls asleep.

She wakes to his fingers in her hair.
She looks up, her face directly under his.
He grins at her tiredly, eyes still slightly clouded with sleep. "Morning, gorgeous," he mumbles cheekily.
She sits up so fast that she squeaks and falls off the bed.
While he's chuckling at her, she scrambles up, distinctly ruffled. "You're awake," she says dazedly.
He rolls his eyes at her. "Nah. Still asleep, Nat."
She pokes her tongue out at him and goes to tell the hospital staff.
Clint stops her. "How long was I out?"
"Five days." She hesitates. "Why did you choose now to wake up?"
Clint shrugs, or shrugs as much as he can all wrapped up in a bandage and tucked in bed. "Dunno. Felt a big, warm lump on my side. My brain cleared a little then because I figured it was you, I guess. I mean, who else would it be? Figured you must've been desperate to climb into bed with me." He smirks as she glares at him. "Guess my thought process improved once I felt you there. Enough to wake me up. I dunno. I'm no scientist."
She doesn't quite know what to say, so she goes back and kisses him on the cheek. "Welcome back, Clint."

"How the bloody hell should I know?" she mutters. She stalks over to the room he's shouting from. "Clint, honestly, you should really- What are you wearing?"
He's bent over in his sock drawer, presumably looking for socks. She's used to this; he's been doing almost exactly this since they started spending more and more time in Clint's apartment. The difference was that he was wearing a suit.
Clint reaches to the very back of the drawer and grasps something. "Gotcha!" he says. He turns around and walks up to Natasha.
Natasha freezes as he sees what's in his hand.
Clint gets down on one knee.
Natasha starts to say, "Oh my God.."
Clint grins. "Nat, we're basically living together now and we've know each other for so long... You know I'd do anything for you." He gestures at his chest, where a bandage is still wrapped, albeit smaller than it had been a month ago.
"Natasha Romanoff, I love you. Marry me?" He cracks open the little velvet box to reveal a gold band with many small diamonds studded along its length.
Natasha's eyes are wide and and her mouth is open. She finds her voice. "I- When you semi-proposed that time when you were drugged and injured, I... I didn't think you were really serious."
Clint waits nervously, fidgeting with the box.
Natasha squats down to sit on her knees so she's eye level with Clint. "Yes," she breathes. "I'll marry you." She leans forward and kisses him softly.
Clint's face breaks into a huge, goofy smile, and he fights to keep his cool.
"Really?" The word slips out before he can stop it and he claps his hands to his mouth.
Natasha laughs at him, a little giddy. "Yeah, Clint, really."
"Brilliant!" He looks like a small child again, she reflects with a twinge of happy nostalgia. "Do you like the ring?" he asks her, uncertainty crossing his face. "I mean, the diamonds aren't huge, but I thought you'd want something practical, so there aren't any big bumps in it and it can be covered up with gloves or armour or suits without leaving a lump, but if you want a fancy one with a big diamond, I can do that, I mean-" He stops rambling as Natasha leans in and kisses him again.
"Oh, shut up and kiss me," she mumbles around the kiss.
She feels him smiling. "'Kay, I'm cool with that," he answers.