"Doctor!"

"Mr. Stark," Dr. Banner said, nodding as he walked inside of the door. It had been two months since he had been introduced to the brilliant playboy billionaire, and he had grown used to the experience of doing his side experiments alongside the other man on the top stories of Stark's research building.

"It's been too long," Stark said, and added, as he always did: "Please, call me Tony."

"Thank you, Mr. Stark," Dr. Banner said, laying his bag on the nearest table and ignoring Stark's teasing grin.

It had been too long. A week and a half ago, Dr. Banner had received a phone call from one of Stark's assistants saying that Mr. Stark would regrettably be unable to open his labs up to visitors, as he was engaged in a particularly involved research trial. Bruce Banner had not known how much he had enjoyed the biweekly time spent doing research with a partner until it had been taken away from him. A solitary man by nature, he had not quite understood the feeling of loneliness. Until now. It was a strange feeling, and he was glad to shake it off.

"I'm sorry to have kept you away for so long," Stark said, his manner belying an odd sort of awkwardness. Tony Stark was never awkward. He leaned on the table next to Dr. Banner. "You must have missed my company."

"This technology is incredible," Dr. Banner agreed. "Second to none."

"I meant my personal company. Of course, that too is second to none." The billionaire flashed a perfectly charming grin, and the awkwardness evaporated, if indeed there had been any to start out with. "Or so they tell me."

"Indeed," Dr. Banner said, pulling out his computer and connecting it to Stark's lab console. The billionaire was good company. The only company, in fact, that Bruce had let himself grown attached to. It was too difficult to suppress his inner beast when emotions were involved, and so he had created a shell, trying to keep everyone out-where it was safe.

Tony Stark-well, Tony Stark was different. It was nice to have someone around to bounce ideas off of, someone who was an intellectual equal, someone whose personal charms were able to allay the coldness of the doctor. And Bruce knew that he was cold. It was necessary. But Stark, of all people, didn't seem to mind.

"Aren't you just dying to know what I've been working on?" Stark asked. He tilted his head to one side. "Tell me. You've been going mad with sheer anticipation of my brilliance."

"I've been doing my work," Dr. Banner said, refusing to let himself get pulled into Stark's charm. But there was something else in the man's voice, something that Dr. Banner recognized as nervousness. Nervousness mixed with pride, an odd combination for Tony Stark.

Stark put his hand on Dr. Banner's shoulder. "Come, let me show you. I think-" he said, guiding Bruce to the stairwell, "-I think you're gonna like this."

In the bottom stories of Stark laboratories were the experimental nuclear chambers, built subterraneously to withstand a meltdown should anything catastrophic ever happen. The city government would never have granted Stark permission to build these labs, but Stark never asked permission.

Dr. Banner thought that he was crazy to try and hide such a large laboratory, but he was grateful for the opportunity to study gamma radiation without having to drive three hours outside of the city to a nuclear plant with limited research capabilities. Of course, Dr. Banner thought Stark was crazy to let him get anywhere close to his nuclear labs, given his potential for destruction. The monster inside Banner-the other guy-wouldn't blink at shattering a nuclear core or two. The fact that Stark let Dr. Banner inside the bottom floors was either a demonstration of pure trust or of sheer irresponsibility on the part of the playboy billionaire.

Either was acceptable to Bruce, as long as he was able to continue his work.

Now Stark opened the door marked "Maintenance Closet" and pressed his hand against the wall, entering the passcode before the steel door hissed open and let them into the elevator. Once inside, he turned to Banner and smiled, and there again a flash of nervousness passed across his face. Dr. Banner wondered what on earth could possibly make Tony Stark nervous.

Walking out into the lab, Bruce noticed that the back wall had been converted into a chemical lab, and Stark now led him there, his hand pressed confidently against the doctor's back.

"This is all experimental, of course," he said, gesturing to the vats of bubbling liquid.

"Uranium enriched?" the doctor asked, leaving Stark and circling the equipment. "This reminds me of my previous research on my condition."

"Yes, the experiments that failed," Stark said, not bothering to blunt his words, something for which the doctor was always appreciative. "I've been doing some work on them myself."

"Yes?" Dr. Banner said absentmindedly, looking at the distillation chamber.

"Yes," said Tony Stark, and there was something in his voice that made the doctor look back at him. He had a curious smile on his face and when he spoke, it was with uncharacteristic modesty.

"You see, I think I've figured it out."

Dr. Banner froze where he stood.

"Figured it out?"

Stark walked over to him, pointing to the tubes next to the distillation chamber. "It was a problem with the midreaction distillants."

"They were unstable," Dr. Banner murmured, looking back to the chambers.

"Only if you let them stand for more than a few milliseconds." Now Stark leaned forward with unabashed excitement. "I figured out a way to separate the reactive elements out-"

"How?" Dr. Banner asked.

"That wasn't even the coolest part," Stark said, now almost giddy with explaining. "Once that was done, they kept refusing in the fifth reactive step, so I had to build a heavy metal extractor to remove them immediately."

"How?" Dr. Banner asked, Stark's excitement contagious.

"Look," Stark said, putting a hand on Bruce's shoulder. "I'm not sure this works. At least, not yet. There's not many experimental subjects I could try this out on. But that's why I wanted you here."

Bruce's heart dropped in his chest.

"You want to test it on me? Now?" He was thrilled at the prospect. Thrilled, but also terrified. It had been so long that he had been living with the monster inside of him that he paled at the thought of trying to erase it.

"Carpe diem, that's what I always say," Stark said, looking into the doctor's eyes in a moment of seriousness. "Unless you don't want to."

The words were a challenge, but the doctor simply nodded.

"Yes."

Stark grinned. "I knew I'd win you over."

The machines were set up and Tony Stark had evacuated the bottom floors of the building, citing a chemical spill that necessitated cleanup. Dr. Banner didn't want to ask how many millions of dollars Tony Stark was losing by sending half of his employees home early for the day, but he was utterly grateful for the man's insistence. He had abandoned hope so long ago that it scared him to begin hoping again now. It was only Stark's perseverance that convinced him to stay now.

Preparations were intensive, and Bruce waited patiently, his heart pounding as he watched Stark work. Stark worked carefully, patiently, and professionally, giving Dr. Banner confidence that he was doing the right thing by allowing the man to test the potential cute on him. The only lapse came when Bruce stripped down naked to climb onto the medical table and Stark averted his eyes.

"Not used to working with the human body, Mr. Stark?" Bruce said, trying his hand at teasing.

"Not like this," Stark said, pulling the straps over his arms and legs. His hands were strong, but when he brushed the doctor's skin inadvertently the fingers drew back, as if touching a hot stove. Bruce was surprised at how gentle he was when inserting the IVs, although he could sense that the man was nervous. About the experiment, no doubt.

Tony Stark looked over him once more on the table, his eyes flicking over the doctor's body.

"You're nervous, Mr. Stark," Bruce said.

Stark looked up into his face.

"It's not the experiment, Dr. Banner, I can assure you." Tony Stark cleared his throat. "You're a very attractive man. Almost as attractive as me." His hands moved over the lines, making sure the machines were set up correctly.

Dr. Banner's mouth dropped open slightly. That was it? He hadn't thought anything of the man's flirtatiousness-thought that it was simply Tony Stark being Tony Stark-but now, thinking back, he was not shocked by the revelation so much as the fact that he had missed every sign.

Not knowing the right thing to say, Dr. Banner merely kept his mouth shut. Stark checked and double-checked every piece of equipment, and then went back to check again until Bruce finally spoke up.

"The lines are clear, Mr. Stark. Or they were two minutes ago when you last checked them."

"Just making sure," Stark murmured, his attention focused on the machines. "But please. Tony."

Dr. Banner heard for the first time in the man's voice a hint of need, and he acquiesced.

"Tony." Saying the name, he was struck by how safe he felt in the man's hands. Even now, strapped to a machine which was about to pump irradiated chemicals into his bloodstream, he was comfortable, almost giddy.

Stark came over to his side and put the final strap in place across his face. His hand lingered on Bruce's cheek, the fingers gently brushing his skin, and the doctor shivered as the gentle touch sent his nerves afire. He was not used to being touched in this way, and with his adrenaline already running at full blast, such tenderness only served to make his senses more acute.

"Bruce," Stark murmured, his fingertips tracing the doctor's chinline. "I hope I don't kill you."

Dr. Banner swallowed hard as the billionaire flashed a quick smile.

"Don't worry, you just let me check these lines one more time. This is gonna hurt like a bitch but you just keep your temper and everything will be okay." He moved briskly now, setting the machines to standby. "And...we're ready!" He looked over at the doctor with eyes that asked for permission.

Bruce's heart was beating fast, whether from the attraction he was feeling or the fear of the unknown cure that awaited him he did not know.

"Yes," Dr. Banner whispered. "I'm ready."

The initial shock of the irradiated chemical tracers wore off almost as quickly as they came, but Bruce felt the aftereffects of the radiation lingering in his body, sending shooting pains down his legs and arms. He jerked under the straps involuntarily as the radiation field intensified.

"How are we feeling?" Stark said, swinging over to another machine to check on the doctor's vital signs. "Pain? Anger? Tell me none of that last one."

"'S alright," Bruce said, through clenched teeth. It wasn't alright, not by a long shot, but he knew that the procedure was the only way to eradicate for good the neuronal connections that caused his emotional swings to release his other side.

The other guy.

He winced in pain again and felt his arms move without his control. This was dangerous. If he let his body get away from him-if he let the other guy get control-there was no telling what could happen.

Bruce blinked hard as the radiation worked its way through his blood. He could feel it now, deep inside of him, wrenching away at that partition that he had worked so hard to develop. He gasped and his heart rate jumped up. A sensor began to beep.

"Easy there, now," Stark said, moving to turn off the sensor. "Just a few minutes more." He pushed himself out of his chair and came over to Bruce's side. Bruce swung his head away from the man, not wanting him to see the fury that was boiling behind his eyes. Sweat beaded on his brow as he tried to maintain control, but the flashes of pain lowered his defenses. He felt the other part of him, the angry part, pressing against the doors.

Another sensor went off. He was scared now, the trickles of sweat rolling down his neck as he thrashed under the straps. The other guy was pushing through, slamming against the doors inside of him, and he was having a harder time pushing back. His heart seemed to beat through his chest as the flames of pain coursed through his nerves roughly.

"Bruce. Bruce." He heard the words as though from a great distance, the voice indistinct, blurry through the pain. He snapped his head back to the side and saw Tony Stark's face looking down at him with worry. His vision swam for a second and he felt the other guy beginning to take over. His arm swelled and the strap broke. Easily, too easily. Pure strength moved through him and he tamped down the rage that accompanied it.

He was terrified, not so much for himself as for the man who was now adjusting the controls on the irradiation lines. He reached out his hand to tell him to stop, to tell him that the experiment had failed.

"Not long now," he heard Stark say, but he was already falling away, falling back and letting the other guys through, his hand waving in the air in mute warning. He opened his mouth and a growl escaped, the sound reverberating through the room full of metal equipment.

He felt pressure against his skin and looked up to see Stark holding his hand, clasping it tightly between his. Bruce shook his head. He could crush his arm with one fist. Didn't he know?

"Not long now," Stark repeated, and his voice was kind. Bruce looked up at him in supplication, fear tearing across his mind and making it blank with pain. His voice was an incoherent garbling of syllables, and he bit down on his tongue, tasting blood. His eyes were clenched as the monster Almost there-almost there-

Then a strong hand grasped his chin, tilting it upwards. He opened his eyes just in time to see Stark leaning over him before his mouth was pressed into a kiss. His eyes widened in shock and he felt his body responding, torn between pleasure and pain. In spite of himself, he pressed upwards into the kiss and felt it deepen, Stark's hands moving over his body in ways that were decidedly inappropriate for scientific work.

His mind cleared. The partition snapped shut on the beast as Stark leaned back, breaking the embrace. Bruce panted, a sheen of sweat over all of his skin. He felt his nakedness acutely, but the embarrassment of his arousal was infinitely preferable to the alternative. That alternative, of course, being death and destruction.

A buzzer went off; the lights above the table blinked and were extinguished. Tony Stark smiled.

"All done!" he said, moving away. Dr. Banner caught his arm.

"Done?" he croaked.

Stark sat back down beside him. Bruce could feel the irradiation still in his body, but the pain was receding, ebbing back into his limbs and bones as just a faint trace of what it had been. And the anger was gone, all gone.

Bruce tested himself, opening up the partition and looking inside of himself to see if the other guy would emerge. The anger was there, always there, but now it wasn't, just an empty place that was void of emotion.

When he refocused his eyes, he saw Stark looking at him with concern on his face.

"It's gone," he whispered, and saw Stark's shoulders move in relief.

"Well, that's a cool million in research I'll never use again," Stark said, the sarcasm hiding something deeper as he moved to untie the straps over Dr. Banner's body. Once Bruce's arms were untied, he helped unsecure the IV lines and found that his fingers were trembling, along with his whole body.

He stood up and stumbled on legs weak with pain, but Stark was there, catching him immediately and lowering him back down to the table. Bruce's body was still in a terrible state of arousal, and having the other man so close to him right now only heightened his lustful state. He breathed hard, his hands on his knees.

"Easy there," Stark said, in a voice that pretended admonishment even as his hands moved to steady the doctor. "Is this how you repay me for a successful cure? By playing hard and fast with the results of the experiment?"

Bruce looked up into his face and Stark raised his eyebrows.

"Of course, if you want to repay me-

Stark never finished the sentence, for before he could say anything Bruce had reached out and grabbed him by his lapel, pulling him into a hard kiss. He felt the other man tense up, then release. Stark's mouth moved against his and he ran his hands down the man's back.

"This must be...an unintended...side effect... of the experiment," Tony Stark murmured, as Bruce moved down to kiss his neck. "Ah!"

Bruce smiled against Tony's skin, noting the spot. It was unusual for him to be able to indulge in strong emotions, and now he reveled in the fact of his lust, wrapping his arms around the other man and holding him tightly. Enjoying the way Stark's muscles moved under his hands, responded to his touch. He felt the other man's cock beginning to harden against him.

"Doctor," Stark said, pushing back from the embrace. "I'd hate to stop things just as they're getting fun, but I don't want to take advantage of you in a weak state-"

In response, Bruce threw Tony Stark back onto the table, pinning him down with his arms. When he breathed, he felt the other man's body move against him, making him even more aroused.

"I'm never weak," Dr. Banner said, following his words with a long hard lick that began at the base of Stark's neck and ended with a shudder just under his earlobe. "And feel free to call me Bruce."

With a grin, Stark arched upwards into Bruce's embrace. His clothes flew to the floor as the two men rolled across the table, their hands moving over each other's bodies as though there were no time left. Bruce felt strong, so much stronger now that he did not have to focus on keeping his emotions in place, and he held Stark down as the man writhed under his grasp.

It was strange to be able to sink completely into lust, a delicious feeling, and Bruce shivered as Tony rolled over to give him access.

"Don't go changing halfway through now, Bruce," Stark said. "You're going to split me in half already as is."

Bruce's cock twinged as he pressed against Stark's back. The man's body was perfect, tan and muscle, all curved planes and lines that spoke to the care he took of himself. Then the man shifted back, pushing into him, and Bruce felt his cock come to rest against the tight hole, his cock already weeping from want. He breathed hard with desire.

"Please," Stark whispered, and the admission of vulnerability in his voice made Bruce wild with lust. He thrust himself in deeply, the flesh tight and sweet against his shaft. Friction, delicious friction. He had not known such ecstasy in years.

The man under him bucked and he held on tightly, thrusting harder. He heard Stark gasp with delight, rocking back against him and pushing him ever deeper. His swollen cock worked back and forth, burying itself in the sweetness. He heard cries of pleasure that he could not recognize as his own.

Moaning, he thrust faster, increasing the tempo as the man's body slid against his, slick with sweat. He clasped Stark's chest as he moved, not wanting an inch of distance to separate them. His hand found Stark's shaft, already throbbing and fully erect; his fingers explored the length of his shaft. Tony Stark began emitting soft cries, making the doctor impossibly aroused. His hand slicked back and forth, working in tandem with his thrusts which made the pressure inside of him grow to beyond bursting.

Now both of them moved in deep synchrony, their moans of lust echoing in the empty lab. Bruce felt his heart tear out of his chest, his emotions finally able to find themselves without fear or caution. Rocking into the man under him, he felt the cock under his fingers jump and jerk once, then twice, spilling hot come over his fingers. This threw him over the edge of desire, and he buried himself into the man, jackhammering his cock deep into Stark's body until he felt the coiled lust inside of him unclench and erupt. He spasmed again and again into Stark's ass until he was spent.

Letting himself fall to the table, he breathed hard as Tony Stark turned to him, planting a soft kiss on his forehead.

"You-" Dr. Banner said, his fingers running through the genius's dark hair. "You-are amazing."

"I must just be the world's greatest scientist. Improvisation, saving the experiment. Saving lives," Stark added, raising his eyebrows in self-congratulation.

"You kissed me." Bruce frowned. "How did you know that wouldn't make me angry?"

Tony Stark looked into his face and grinned. When he spoke, every word dripped with his famous charm.

"Because, Doctor," he said, his capable fingers tracing circles on Bruce's skin. "I'm also the world's greatest kisser."

Dr. Banner smiled. He looked forward to seeing what else Tony Stark was great at.