Inspired from a Tumblr post from YEARS back:

"Bucky manages to avoid being found until one night, with no warning, he shows up in Tony's kitchen. Tony is understandably kind of alarmed when he finds an assassin sitting at his table, but Bucky just kind of holds his arm out toward Tony and very quietly tells him, 'I don't know how to fix myself.'"

Takes place post-Captain America: Winter Soldier.

Tony stood in shock at what he was witnessing.

His right hand hovered over the light switch, the other clutching the door handle for dear life. After talking to Steve for months, begging for the details on how him, Natasha, and Sam had managed to bring down the entirety of SHIELD, he would be an idiot to not realize that James Buchanan Barnes was occupying his kitchen.

Nazi assassin Barnes.

With the metal arm of death.

Right.

Suitless and scared shitless, Tony slowly inched forward feeling the intruders eyes watching his every move.

Tony cleared his throat. "Anything to drink?"

He did not expect an answer but the awkward air was becoming quite uncomfortable. When it seemed as though there was no answer coming, he tried a different approach.

"Did you come to kill your boyfriend?" Tony smirked as he leaned against the counter, his arms crossed upon his chest. "Because I can tell you now I'm not going to let that happen."

Tony could swear he saw a small smile break across Bucky's face but he couldn't say for sure. The man, however, did nod his head from side to side in a gentle motion.

The genius was stumped. If not to kill Steve, then what was he doing in Avenger's Tower?

As if he had read his mind, Bucky slowly yet deliberately held out his mangled and torn metal arm. Through the long hair and the dark circles on his face, it was easy to see the sadness flash across his face as he confessed, "I don't know how to fix myself."

It felt as though the room was holding its breath in anticipation to Tony's response. He looked at the fallen hero and in doing so found a humanity he could trust.

Sighing, he pulled a small tool kit from a nearby cabinet. "I swear, if you try to kill me, I will bring Steve down here to kick your ass again."

This time, Tony could see Bucky let himself smile.