In hindsight, it was probably obvious.
But while it happens, it's really not, even if Natasha should have been able to read the signs. But Darcy is touchy with everyone, even been known to lay a hand on Fury's shoulder in a tense moment. She doesn't exist in anyone's chain of command, except for Jane, and if it weren't for how pervasive she is, like a weed growing wild in their social calendars, she'd be a no one at all.
And James and Steve have a natural gravity to each other. They'll fall in line, with Bucky following Steve through the ends of the earth, so nothing seemed out of normal. They came from a demonstrative time, the reserved fifties never really hitting each other of them. Steve might be straight-laced but he's not uptight. When Bucky came back the second time, after he'd recovered and then after he left to find himself (or more likely, to shoot things until he felt better, someplace far away from anyone he's known or wronged), he fell right back into old habits.
They leaned, they fought, they navigated a world of different treacheries together, things they only imagined as children and things they never thought of even then. So Natasha never thought anything of the time the men spent together. She's been navigating her own relationship with James, and found her heart so hard had changed so much about them.
He's not the James she knew, and he's far more willing to be Bucky.
In hindsight, it really should have been obvious.
The first time when James came back, when he spent his days pouring over history texts and figuring out his place in the world, he grasped for anything familiar, anything that brought a happier memory. And he made his play for Natasha, a desperate kiss in the gym, trapping her to the mats in a elegant move. It was nice, it was hot and it was a breaking in her mind of all the things she remembers all too clearly.
They were both too much of the same cloth, the same magnetic centers. Too similar and she had to push apart. He ran.
The second time he came back, it was with a casual contenance and a slink again in his step. It's part artifice and part, she couldn't put quite a finger on it, but it was akin to acceptance.
He fought a war in himself and he chose Bucky, he chose Steve. James did not choose Natasha, did not choose to hang on to his ledger.
Bucky takes up his job again, going into the places that Steve never could. He can shoot and spit and lay waste, for love of country and love of being useful and in the right. Steve is America ideals, apple pie and golden waves of grain. Bucky, Bucky is the cynical, sharp tongued scavenging America, who eats glass to survive.
And Darcy comes into both of their lives as America as it is, glossy and sarcastic, a little too much and yet, everyone wants to devour and drink it in.
So really, in hindsight, Natasha is downright stupid for not seeing it coming.
But Darcy is touchy, and Steve and Bucky have been and will always be magnetically pulled together, and as Darcy invades everyone's lives and personal space she draws a more genuine smile from James.
Natasha should have seen it coming the day James returns Darcy's touch and not with his flesh hand, but with the bionic one, the one that is more sensitive than he ever lets on. James and Steve study history like tacticians, and can pull threads that no one else sees, but Darcy is the one that puts it all into context.
She doesn't think much of it then, Darcy and Bucky playing a trivia game in the common area, neither of them winning because there's so much neither of them know. And that turns into Darcy falling asleep with her head in his lap after talking about how it feels like her life is at this weird state of standstill, waiting out the recession with a halfway decent job, rather than toughing it out in grad school like her classmates.
She didn't think anything of it then, but now she can see them in her head, his fingers combing through Darcy's hair almost in reverence as she sleeps.
Hindsight is 20/20.
Because the closeness and the jokes between Bucky and Steve only get worse, and they only spend more and more time together. It always seemed to be some combination of the three of them together. That was good, that was normal. Darcy's just barely younger than them, technically speaking, and Natasha's older, also technically speaking. James still spends time with her, they are still close friends, partners even, and it would be foolish to see another woman as a threat to that.
Darcy's sweet after all. She makes cookies and food from scratch, leaves paperback books around when she's finished reading them, dogeared and the spines cracked, and everyone has snuck at least one back to their rooms to read during the nights they don't sleep.
So she really should have seen it coming now that James has his gravitas back, the dark faced Winter Soldier, and Steve is barely keeping it together. He's rubbing circles into his shield, just waiting for the moment they can go into the scientific supply shop where Foster and Darcy are being held hostage by run of the mill, everyday criminals with chemistry degrees
It's not merely friendship, there's a possessiveness to their anger, that mark of rashness that's keeping them both from being first out of the gate. They don't try to stop Thor from going in, who could, really? But they aren't being held back willingly, and Natasha does notice that they don't hide how they touch and support each other. It's not their normal, boyish shows of affection, the arm slung around a neck as they hurl insults at each other.
This affection is between lovers, and frightened ones at that. That just makes Natasha more concerned, because if these two are nervous, that means there's another variable at play.
There's shots from inside the store, and they are both off like bullets themselves but out walks Barton and Thor, each with a woman held close. Darcy wrests herself away from Barton as quick as she can and she buries herself into Steve. He drops his shield for her, wraps his arms around her and kisses the top of her head, rests his chin there.
Then Steve lets go, and she and Bucky repeat the actions, a refrain of comfort.
"Well, that's just not fair," Barton says, coming up behind her, an arm around her shoulder, "All hogging each other like that."
James doesn't even look to see who is watching, kisses Darcy until her breath actually steadies.
It doesn't break her heart, it breaks her history.