This is what I came up with:
There's a bad fight--three of them, actually. One between Arthur and Cobb, over a long distance phone call, and then next in a bar with a few guys Arthur will never remember. The third one is with Eames, who asks what's wrong with Arthur's face when he stumbles into the hotel room at five in the morning. And the guys in the bar weren't even a challenge, so he goes in on Eames and asks, why do you care, and do you know what it is to lose someone? and I'm wrong with my face, until Eames' face twists into hurt and fury and he shoves Arthur. And it's later, when Arthur is face down on the white hotel bedspread because it's cool against the forming black eye Eames gave him, while Eames is in the bathroom washing out his split lip and trying to clean the blood and dirt off Arthur's dress shirt, because he needs to leave soon and look respectable doing it. That's when it hits Arthur, that Eames just got into a fucking fistfight with him and took a few good hits and gave a few better ones, and in two hours, he's going to get in the cab with Arthur and fly eleven hours over the atlantic while Arthur wears the shirt he's washing by hand in the bathroom sink and he's going to hold his hand too tight, as if Arthur has never been to a funeral before.
It's then, face down on the bed, that he realizes he's in love with Eames. He picks these fights like other people make sad faces or hold their arms open, and even if it's a thrown punch or the slow press of Eames fucking him, a touch is a touch, and Arthur is stupidly, irrevocably, dangerously in love.
Eames knows already, he realized way before. Before the criminal in Arthur made him loose, back when everything made him tenser and Eames made him nervous, and sometimes when shit got really hard for Eames and Arthur just sat there looking like he was on the right side of everything except the law, he'd make these comments to him about how he couldn't possibly understand, or not to worry his pretty head about it, but Arthur would just give him these looks like he cared, and offer a perfect solution.
But for Eames that's like. He's been on his own for so long, handling his own problems and facing all his own consequences with no number two, and it fucking baffles him how Arthur can back him up so quickly, offer him all the answers and the resources to make it happen without even thinking about it at all. Like it's not a problem for him and he'd do it no matter how far away he was or what he was doing. And he thinks about it all the time after this one epiphany, and one day he's cornered, basically, and his fence is going to turn him in.
So he calls Arthur, just too see, because at this point he's fucked anyway--he might as well find out if Arthur would actually save his ass for nothing before he goes to prison for life--and Arthur is asleep, and he's confused and a little angry and he asks why Eames would even call him, because they've only done a few jobs together.
And Eames is like, "The thing is, darling, I'm kind of in a pinch," and he explains in as few words as possible because he's been running to catch his train and he's got a broken rib. Arthur just says, "Okay," and hangs up, and Eames can't believe he thought Arthur would do something like that for him, but twenty minutes later his cell phone rings and it's Arthur, and he says "You should be okay now," and gives Eames an address where he can lie low and tells him who and where to avoid, and never to call him again while he's sleeping."
And Eames is just blown away. All he can say is "Good night, Arthur," and Arthur just gives him that dry chuckle and hangs up, and even though he's tired and he's got a broken rib and a debt bigger than some governments right then, he just keeps smiling and laughing, because. ARTHUR. He's in love with Arthur. It is ridiculous and amazing and he doesn't think he'll ever escape it, and he wouldn't ever fucking want to.