It's Clint who finds the last piece.
He doesn't say a word when he walks back into the lounge with his bow slung over his back, his face still streaked with grime. He'd disappeared after they got back to the tower, and Tony had assumed that he'd gone with the Widow, or fucked off immediately like Bruce had, to melt down in privacy over - Jesus, no, Tony can't even think about it yet - over what had happened.
But no, apparently he'd gone back, sneaked past the perimeter - or maybe walked right through it; who would tell him no? - and searched, through rubble and ash and twisted metal and bodies, god, the bodies were still there - hunted for a glint of dull red and blue.
"Here," he says, pulling the fragment of vibranium out of a zippered pocket in his vest and putting it down on the table next to the others. It's no bigger than his hand, sharp at one end, a streak of red across the top, and Steve stares at it blankly.
The other six pieces are laid out in front of him, forming the rough shape of a shattered circle. Steve had known, somehow, when the battle was over and it seemed like they’d won - "For some value of winning," Bruce had put it - that he didn't have all the pieces. Steve pulled off his gloves and scrabbled at the ground until his fingers had bled, until Thor had put a hand on his shoulder and said, "Come, Captain," and Tony had felt like he was going to throw up, the scent of hot blood thick in the air and the anguished look on Steve's face somehow making it all real, the silence that had taken the place of the screams suddenly so much worse than the screams themselves.
The seventh fragment is clearly the last one; it fits like a jagged puzzle piece among its mangled brothers. "Christ, Barton," Tony says from across the table, his hands wrapped around his fourth glass of Scotch. He lets out a shaky laugh. "Jesus fucking - "
"Thanks," Steve says, his voice steady, his eyes locked on the ragged collection of metal.
Clint shrugs, like it's nothing, and maybe it isn't, compared to the rest of the day. He turns on his heel and leaves just as quickly and silently as he arrived, and Steve just stares.
Tony falls asleep on the couch sometime after midnight; he doesn't mean to, but exhaustion and alcohol win over adrenaline and he slips into a dream, all heat and the crunch of metal and Bruce disappearing into the ocean and Clint jumping before Tony can be there to catch him and Steve lying in the middle of the street, his eyes blank and staring, and Tony hears a ripping sound and it's his suit, they found him, they found him -
Tony wakes with a scream halfway up his throat. He's never been someone who experiences the beautiful freedom of momentary amnesia upon waking: he knows exactly where he is, knows exactly what has happened, can feel every remembered fingertip pressed into his skin. It's still dark; he can't have been sleeping for more than three or four hours. The ripping sound happens again, and Tony blinks in the direction of the dimly lit kitchen.
Steve is still sitting at the table. There’s a roll of duct tape around his wrist, and he’s tearing pieces of it with his teeth and lining them up on the edge of the table.
Tony's stomach sinks. He stands up off the couch and stretches, yawns loudly enough that Cap definitely hears him. He pads over to the table cautiously, approaching Steve like he's a wild animal, because maybe he is right now. Tony doesn't know for sure.
Steve's taken off his uniform and showered; his hair is damp and he's scrubbed the blood and dirt from under his nails. Tony wishes, all at once, that he hadn't woken up at all. He wishes he'd never had to see Steve brought down to his basest level, his chest cut open and his guts spilled across the table.
"You look like shit," Tony says.
Steve snorts and lines up two pieces of the shield on the table with his large, steady hands. The break was sharp and clean, and Steve takes the first piece of tape off the table and lays it down carefully, almost reverently, over the shield.
Tony doesn't know what he expects - maybe for it to sizzle, or burst into flames, or reject the tape like a body rejects an organ that doesn’t quite belong - but nothing happens. They both stare down at the shield.
"Cap," Tony says slowly, "Why don't you get some sleep, and I'll take a look at it, see what I can - "
"No," Steve says, and rips another piece of tape from the roll with rather more violence than necessary.
Tony passes a hand over his eyes. Everything is falling apart, everything has fallen apart; the team is as shattered as Steve's shield if Tony fucking Stark is the one pulling Captain America back from the edge. Tony's hands are shaking and he's flown into space with no intention of ever coming back but he's scared and he knows, suddenly, that if he fucks this up it will be the end of all of it for the team, that there will be nothing that can put them back together.
He watches Steve’s hands slide the pieces of the shield over the table, rearranging, making them fit back together in a way they maybe never will again, but he’s trying, he’s taking it into his own two hands and doing his absolute fucking best and failing miserably and Tony knows exactly what that’s like. He puts a hand on Steve's shoulder and squeezes. "Okay," he says slowly. "Okay, then. Can I help?"
Steve pulls the piece of tape from his mouth and sets along the edge of the table with the others. He picks up the smallest piece of the shield, the one Clint brought back, and holds it in his hand tightly. Tony wonders if the edge of it feels like a razor blade pressed into the skin of his palm. He rubs his thumb in small circles over the side of Steve's neck and hopes Steve can feel everything he wants to say.
Steve sucks in a deep breath, and when he exhales, he sets the sharp piece down on the table.
“Sure,” he says. “That’d be nice.”
So Tony sits down next to Steve and smooths down duct tape over the most valuable piece of Americana in existence and Steve’s hands are steady and somehow, when Tony isn’t paying attention, the sun comes back up.