It doesn't start where logic says it should have.
It doesn't start with Clint and Phil: their relationship is as professional as any relationship with Barton can be. Handler and specialist. Uptight pedant and loose cannon. Outrageous flirting and disapproving silence. That's not where it starts at all.
It starts with Phil's arm under Bruce Banner's bare ribcage as they heave him into the back of a nondescript SHIELD car, naked except for the shredded remains of his trousers hanging off his hips, and the half hour of semi-lucid conversation that follows. Mostly, Phil tells him that he's going to be all right, that they aren't going to hurt him, and asks him about his research when reassurances falter. Bruce talks on autopilot at first, then his hands start to move and his eyes light up, and Phil's more than a little bit intrigued by the time they drop him off in medical.
It begins, actually properly begins, with Bruce's nose in his hair and his mouth almost on Phil's jaw, lower lip resting in the dip between face and neck. They've been circling closer for months, between start and beginning are a lot of quiet conversations, almost reaches, awkward greetings and lost evenings. They keep similar hours; Phil spends most of his life on site at SHIELD (wishing there were more hours in the day) and Bruce can't leave (he wants more hours in the day too though, they've talked about it and decided that another six would be ideal) and their individual orbits start brushing, then crossing, and suddenly there's a routine.
Suddenly, Bruce is sitting on Phil's office couch most nights, clipboard stacked with paper from the printer and balanced on his knee, a blue pen twirling idly between two fingers, and they're having conversations.
They're interesting conversations. Phil starts looking forward to them. Bruce starts eating dinner in the cafeteria with him. His hands wave delicate emphasis and his eyes light up and change his whole face, and it hits Phil, unremarkable Phil Coulson in a blandly well cut suit, that Bruce Banner is actually, legitimately, completely brilliant.
He's always had a thing for that; unusual brightnesses, uncanny skills, sharp blades that cut on both sides draw him like a moth around a flame.
There's definitely a vibe. A feeling. Something buzzing in the air between their hands that never brush because they're both too cautious, too aware. Whatever it is, it's there, and Bruce spends all his time biting his lip and Phil tries not to say anything too stupid or too classified, and it seems to be going well. One night, sitting on the lumpy black cotton-covered couch, Phil puts his hand in Bruce's hair and rubs his fingertips over his scalp. And that's how it begins.
It doesn't end, or, it hasn't yet, but it has changed.
The change has a name. The change is Clint Barton.
He's been off and on Phil's radar for years, dancing around with careless fingers almost brushing the waistband of Phil's trousers, touches that lingered and brash flirting over the comms. For a while, when he was younger and stupider, Clint's inappropriate behavior was something he held close, a warm memory and a gift and a vague hope for the future. After hearing him mutter similar nonsense down the comm at Hill and Woo and Sitwell, after Fury swats away an attempted hand on the shoulder, after he works out how many handlers got the exact same treatment, the small warm feelings go cold and heavy like lead and ice, pressing down on his lungs.
He can't look him in the eye for weeks, but that's okay because Clint's never been an eye contact kind of guy.
Phil moves on. Or he doesn't, it's hard to say. Barton doesn't seem to notice anything, he certainly doesn't stop, but the lack of notice may be a lie (it is, he notices everything) because now he sometimes hesitates, words almost stumbling blocks, and Phil retreats. It's for the best; loneliness is solid and dependable and then, years later, now, Bruce Banner's hands are never careless and his smile is shy. Phil is happier than he had been for a long time and he doesn't seem alone in this, but there's a space neither of them reach to occupy and they can never quite settle down.
They get close though. Really close. It's probably enough, and the space can just stay there, Phil figures, empty and quiet. He's not even sure what might fit into it anyway.
One evening, Bruce tells him how Barton has been hanging around in his lab a lot lately. He hasn't broken anything yet, he's generally well behaved, and Bruce pushes his smudged glasses up his nose and asks if he flirts like this with everyone. Phil lets a tiny twist of territorial anger spark in his chest and tells him yes, yes he does, he's incorrigible.
Bruce just laughs. They settle down on the office couch and Phil falls asleep with chemical stained fingers raking through his hair, thinking about Clint Barton; an old dull ache, but an ache none the less.
The day it changes lasts sixty seven hours, starts on Thursday at eight am and finishes in the small hours of Sunday morning when Bruce staggers in from the medical bay, wearing only his trousers and a blanket. He doesn't look too much worse for wear, just exhausted, slumped on the couch. Phil's got some impressive bruises and six stitches under his hair but they're both okay, and huddling under Bruce's stolen blanket, careful hands and slow breathing, is really a way of confirming that they're alive and here and mostly whole. The empty space hangs over them, this time echoing with things they'll never say with words and can't say with their hands. Most days it's enough, but today it isn't.
Phil tells him: I don't know what to do, I don't know what I can do, I think something is wrong here. Bruce leans forward, blanket slipping down his narrow back, and breathes deliberately and loudly with his elbows on his knees. He's not going to change, Phil's never been afraid of that, but everything else has changed and their arms aren't pressed together any more, the easy silence is getting thicker, more like water or sand, grating with every breath.
Phil waits so long for Bruce to say something, thinks twice three five ten times about everything he could say (I love you and I wish I could make things easier and you make me feel inadequate but also like I want to try to be and I can never be enough for this) and falls asleep, eighteen inches of empty space between them. It might as well be an ocean and a chasm and a million years. Bruce's face is closed off and his hands, the best barometer of his mood that Phil's ever found, twist in the blanket hem and grip awkwardly at his knees, nails gouging over already reddened knuckles. He stares at this until he falls asleep.
When he wakes up, it's light through the white plastic blinds. He's not wearing shoes or his tie, and there's a blanket over him, a warm chest gently shifting beneath him and a half second of pure hot relief (it was a dream) until he realizes that Bruce doesn't have muscle like that, doesn't wear hoodies, doesn't twist his fingers through Phil's short hair that way.
It's Barton, Clint, and he doesn't let go when Phil leans away, just smiles a bit, sleepy and friendly, and says good morning, sir. He's dusty, plaster clinging to his hair and neck.
His other hand is on the back of Bruce's neck, lacing through his hair while his thumb rubs circles into his skin. Bruce is lying on his side, face pressed into Clint's abdomen and body curled protectively around his own hands.
You two are hopeless, Clint says fondly. His blond hair is sticking up at all angles in tufts. The cold weight in Phil's chest lightens a little, warms just enough that he can breathe, and when he puts a hand over Clint's on the back of Bruce's neck (he hums, pushes back into it, Phil's hand is bigger, Clint tips his head so their foreheads bump lightly) there is no sense of empty space, no echo of doubt in silence and enough hands to say everything.