Natasha Romanoff appeared in front of Bruce one eyebrow quirked and a cup of steaming coffee clutched in her left hand.

"Are you done yet?" she asked.

Bruce glanced over his glasses and gave her a small smile. He shook his head.

Natasha shrugged. She handed him the coffee, saying, "That's what I figured."

Doctor Banner took the mug, wrapping his palm around its center and inhaled the scent deeply. The heat of the liquid danced across the bridge of his nose, stinging the skin beneath his eyes, but somehow woke him up. He blinked the steam away and carefully placed his lips on the edge of the cup. He took a sip.

It burned going down, but God it tasted good. Bruce set the cup down on the edge of his desk and smiled again, "Thank you, Agent Romanoff."

Natasha suppressed the urge to roll her eyes. She walked around the length of the desk and perched herself next to Bruce's computer. The Doctor found his eyes wandering between the screen and the beautiful Russian. His gaze settled on Natasha.

Agent Romanoff found a small smile gracing her lips as Bruce's eyes landed on her. A flash of pink filled his cheeks. God, he was adorable.

Taking her finger, Natasha traced the length of his jawline and tipped his chin up. She leaned down and pressed her lips to his.

"You make it so hard to focus," he mumbled against her mouth.

Natasha pulled away. "You know," she said, "When you have trouble focusing, it's usually a sign that you need to take a break."

Bruce rolled his neck from side to side. He adjusted his glasses and sighed. "Natasha," he said, "as much as I would love to take a break, I have to get this done."

Natasha licked her lips.

"Fine."

She stood and began to leave the lab, knowing Bruce's eyes were following her. She had just made it to the door when the realization dawned on him. "Are those my clothes?" he asked.

The agent turned around, a smirk pulling at the corners of her lips, "Took you long enough to notice."

Brue swallowed audibly, "Forgive me, Agent Romanoff, I was quite busy… but now. Well now…" His voice trailed off as he stood and crossed the room. Two strides later and he was standing in front of Natasha, eyes dark in the otherwise brightly lit lab.

He took three deep breaths. Taking his hand, he allowed two of his fingers to skim the hem of his shirt, careful not to let their calloused tips touch Natasha's skin.

"You know," he whispered, voice dropping an octave, "Purple looks good on you."

Natasha snagged her lower lip between two teeth and chewed on it momentarily. Releasing it, she dropped her eyes before meeting Bruce's gaze steadily.

"I think anything involving you looks good on me."

Her voice was sexy. Husky. Deep enough to allow a shiver to course up and down Bruce's spine, and yet there was a sincerity behind her words. A softness that let Bruce know she was being honest. Truthful.

Any ounce of control Bruce had planned on containing disappeared as he crashed his lips against hers, pressing her back into the lab's door. Natasha arched her neck upward, allowing the Doctor better access at her mouth. She found her hands weaving themselves around Bruce's neck, fingers intertwining.

Bruce's palms lay gently against her hips, hesitant despite the intensity of their kiss. Teeth clashed. Tongues fought for dominance. A soft moan escaped the back of Natasha's throat and suddenly her fingers were running through Bruce's hair, pulling at the curls while forcing him closer and closer. The Doctor pressed his body flush against the Agent's, lips molding against hers. He slid his hands to the small of her back.

The tips of his fingers danced up her spine, under the hem of his shirt. Natasha shivered. He pulled his mouth away from hers, leaving a trail of kisses along her jaw and down the length of her neck. Natasha's breath hitched as he nipped slightly at the skin of the base of her collar bone.

Shoving him off, Bruce stumbled backward, surprised. But then Natasha was pulling his shirt off her head, revealing a lacey, black, bra. His shirt tumbled to the floor, landing in a pile by their feet. The Doctor closed the distance between them once against, allowing for his palms to rest fully against her back, drawing her to him. He kissed the edge of her shoulder, teeth scraping near her bra strap.

"F-fuck." Natasha hissed through clenched teeth as his lips found the edge of her jaw. Bruce suppressed a chuckle, allowing his gaze to drop so he could just pause and take in how beautiful she was. How delicate yet strong. How her lines were nearly perfect, all telling stories he couldn't wait to hear about. His eyes sought the length of her stomach, the curve of each breast beneath her bra, and the slivery glint of a chain around her neck.

Furrowing his eyebrows, Bruce pulled back to get a better look at the necklace. Natasha huffed in protest.

"What are you doing?" she asked. Her breaths were coming in short gasps.

"Where'd that come from?"

Bruce pointed to the charm that lay at the hollow of the assassin's neck. It was small, barely noticeable, yet he was painfully aware of it. A single arrow, about three inches in length, lay across her skin.

Natasha glanced down.

"Oh, that?" her fingers found the worn chain and fiddled with it, "Clint gave it to me."

She took too steps forward and wrapped her arms around his neck in attempt to pull his lips back to hers. But he resisted.

"When did he give it to you?"

Natasha frowned, "Does it matter?"

Bruce didn't answer. No, it really didn't matter. But in a way it did. How had he never noticed it before? How had Natasha not told him about it? Why had it never come up?

He knew he was being stupid. Irrational. But seeing the archer's symbol splayed across the skin of his girl, it evoked something in him he couldn't quite explain.

Natasha dropped her hands and sighed, "It's from Budapest."

"The same Budapest that has come up in conversations before?"

"There is only one Budapest, Bruce."

The Doctor held up his hands, begging for her to work with him. To be patient. He was trying to sort through this.

"The same Budapest that you and him remember differently?" Bruce tried to keep his emotion in check, but he could feel the concern in his voice. He could feel the insecurity seeping into his words, his worriedness taking a toll on his rational thoughts.

Natasha blinked in surprise, "It's not like that."

"Then why haven't we talked about it before?"

"Because there's nothing to talk about, Bruce."

"Well obviously there is if he gave you a necklace that you're still wearing." His words came out sharp. Harsh. God he needed to get a grasp on things. To shut up. To just grab Natasha and kiss her stupid until his mind shut down and they both forgot about this.

"He's my best friend."

"I've heard that one before."

Natasha shook her head in disbelief, "He's married!"

"So?"

The assassin's hand collided with the doctor's cheek, the sound of skin on skin echoing off the tile of the lab.

"How dare you."

Bruce's jaw twitched, half in pain, half in anger. His fingers flexed at his sides, threatening to curl into fists. He needed control. He could not afford a code green. Not now. Not over this.

He swallowed thickly and turned his head back to look at Natasha. Her green irises' were narrowed, arms crossed over her chest in offense. She dropped her gaze and her voice, "I can't believe you would think that low of him. And me."

Bruce blinked twice, eyes widening. He took a step forward, trying to grasp her hands in his, but she refused to budge. Any sign of the Other Guy had been pushed aside as guilt coursed through his veins.

"That's not what I meant, Natasha."

She didn't respond.

"Natasha, please."

She ran a tongue across the front of her teeth. Bruce dropped his hands before he began running them through his hair, ruining the already unkempt curls. He paced back and forth, only three steps each way so he could keep looking at Natasha from the corner of his eye.

He paused once he had a firm grip on his words.

"I wasn't trying to imply anything, Natasha. I-I would never try to offend you or Clint." He stopped and took a shaky breath, "Maybe it's because I don't understand your friendship. I've never really had a friend before," he gave her a small, sad smile, "But seeing you guys together…. I guess I just get jealous. You two are so… aware of one another. You know each other's next move before you make them. I've never had that. But I want that. With you. And seeing you, wearing a necklace that represents him… I just got jealous."

Natasha's rigid shoulders softened.

"I know you didn't mean it."

Bruce let out a breath he hadn't realized he had been holding. "I am sorry."

The Agent uncrossed her arms. "You know?" she said, "I knew you had a temper, but I never thought jealousy would become a problem."

Doctor Banner shrugged, "I guess I've got some issues with green monsters."

Natasha tried but failed to suppress a grin.

Bruce took a step forward and grabbed her wrists, "Forgive me?"

Natasha nodded.

"Thank you," he whispered, leaning in and brushing his lips against hers. His hands dropped her wrists and pulled her into a hug. Natasha's red curls tickled his nose as he pressed a kiss into her hair. She turned her face into Bruce's neck and inhaled deeply.

They stood there for a moment, listening to one another's breath. Bruce stared at the doors in front of him, willing himself to memorize the way her body fit against his. To remember how she smelt, and how her chest hitched with every third breath. He allowed himself to smile before he pushed her away so she rested at arm's length.

"So are you going to tell be about Budapest?" he asked.

Natasha rolled her eyes and drew him into another hug, "You wish."