It was supposed to be their secret.
Legs rubbing each other under the communal table, hands brushing when passing in the hallways, falling asleep on her shoulder during the mandatory team movie nights that pulled him away weekly from his science benders.
The kisses she would steal in the elevators between floors.
Her hands sneaking beneath his lab coat and down the front of his pants whenever she would catch him working late in the lab for the third night that week, kisses being peppered along his strong neck and jaw as they stumbled to his old couch as his current obsessions lay forgotten across the steel tables and under microscopes. The lights dimmed and the glass walls turned opaque to shield them from the rest of the world. Whispering soft nothings as she slept in his arms satiated. His life had been changed.
She was too young. He was too damaged. In those moments it didn't matter.
He insisted she continue on with a life outside of the tower. Meet with friends for drinks, go to concerts in the city, and try the new restaurants that caught her eye. She humored him and did.
All without him.
He thought it would make it easier when he left.
He was not blind to the poorly shielded adoration in her eyes during the early days of their relationship that started during the early mornings in the kitchen over tea and coffee that had slowly shifted to one of love and pulled him in deeper than he ever could have imagined. How in the cliché of all romantic poems they were magnets that were always drawn to each other no matter the distance or time spent apart. No matter what she did outside of the tower, she always returned to him at night. A bit of selfishness that she said he deserved and he still refused to believe.
Thoughts about golden rings and eternal vows were abruptly pushed aside as what they had was too pure to be contaminated by the unrelenting critics of their society who had still yet to accept him. It was their secret.
She was as reliable as the sun.
It was why he never imagined she would be the one to leave without a word.
That morning he drank his tea and read the newspaper on his tablet alone in the communal kitchen, assuming she had started her day earlier than he as sometimes happened when Jane was close to a breakthrough in the stars.
He continued his day as always, consumed once again by his latest samples. Nights came and went and he continued on in that void.
It was Natasha who was sent later that week to evict him from his lab to prepare for team movie night. Containers of half eaten food brought by lab assistants scattered across his desk. Bags under his eyes, phone silent despite the number of texts sent, pleas for her to come home. Calls that went straight to voicemail and were not returned.
The couch remained cold.
He was hyper aware in that moment that his life had once again been irrevocably changed and not for the better. For the first time in a year he stayed awake through the movie, silently searching for that something but unwilling to ask. The team surreptitiously observing him from the surrounding furniture, unwilling to interfere.
For the first time since moving to the tower he didn't go to the lab the next day.
He meditated on the last year to see where it went wrong. Flipped through the photos that she had insisted that they take and sorted chronologically into a digital photo album she had gifted him for his birthday. Her eye's bright under her red knit beanie, snowflakes settling on her dark eyelashes as he leaned over her shoulder to be in the selfie during her first winter in New York, strings of colored lights reflecting in the background. Pictures from spring trips to the zoo and Central Park, his eyes always glued to her smile. The summer nights spent stargazing on his balcony, his head resting in her lap.
From there the pictures became more infrequent. He had been getting too close; she had wormed her way in too far.
It was no longer a secret.
Pictures became fewer. For the first time he noticed how the light had dimmed in her eyes. The smiles looked more forced. Her face looked thinner, cheeks no longer naturally rosy.
There were no pictures from outside of the tower.
He had smothered her spark. Forced her slowly out of his life under the guise of caring while still expecting everything from her.
His pity turned to uncontrolled anger. The Hulk proof rooms received nightly testing and the calls to assemble no longer filtered through to his phone. He wanted to leave but he couldn't because she was still here. Sitting on that couch. Drinking coffee out of that mug. She was sneaking up behind to ruffle his curls while he was bent over his computer analyzing yet another spreadsheet.
Her thighs were spread wide on his bed while his tongue coaxed out one more orgasm before he finally slid home to find his own release. No longer able to tell where he ended and she began.
She was always wearing his shirt the next morning as she snuck back to her rooms, a mischievous smile always on her face as she tiptoed out his door.
It was a month later that he was finally approached by Tony and found out where she had gone.
Apparently being on the same planet had become too much for her. She had fled to another world entirely to escape him.
He had known she was leaving to attend Jane's wedding on Asgard as only she and Jane had permission from Odin to travel the Bi-frost for the royal occasion. The celebrations following the ceremony were to last for 2 weeks but she was only going to stay for three days as the longer mortals remained, the harder it became for them to leave. She had let the team know the change of plans only as she was leaving and requested that he not be notified.
She had needed a clean break and the team had agreed.
Months passed before he finally calmed down enough to return to his lab.
Notes from his time spend in his self-imposed isolation drove his research in new groundbreaking directions. Camaraderie with the team slowly resuming as the broken relationships and trust slowly reformed.
It didn't make it hurt less when five years later the bi-frost was once again reopened as the Avengers officially joined forces with the warriors of Asgard lead by Thor to no longer just protect Earth, but the Nine Realms as well.
He saw her for the first time then; as he stood in the back listening to Steve make his speech about new alliances in an ever-changing world.
Standing on the edge of the stage with the Asgard delegation and wearing a gown of hunter green with golden trim, her dark curls longer than ever held off of her face with a golden circlet she stood next to Loki. One arm wrapped around her waist, his other holding a dark haired child on his hip.
For a moment he couldn't breathe as the pain came rushing back and he stood there imagining what could have been.
But then the moment passed.
He saw with clear eyes for the first time the happiness on her face. The roses back in her cheeks, the life back in her eyes, and in that moment he was able to finally let go.
It would always be their secret.