Disclaimer: Half Life and all related characters are not mine. They belong to Valve. I make no money off this - it is purely for shits and giggles.

Author's note: This little story has been bouncing around in my head for a while now, ever since I wrote my previous one-shot, Half-Life: Gravity, and I just wanted to write a fic where our favorite physicist gets a bit impulsive. Yeah, I like Gordon/Alyx. This is set late in the Half-Life 2 canon.

Gordon Freeman (graduated MIT, PhD in Theoretical physics, formerly employed by Black Mesa before it was invaded by aliens and nuked into a glass crater in the middle of what had once been New Mexico) pounded his fists into the punching bag that had been set up in the training room. In truth, it was a scavenged and patched mail sack that someone had filled with sand and sealed off, but it suited its intended purpose just fine. At the moment, it served as a cathartic proxy for every alien menace that he had ever faced. They still haunted his dreams sometimes, the events of Black Mesa in particular, but more recently the events surrounding City 17, the Citadel, and the Combine.

So many people – good people, brave people – had lost their lives during the Resistance. He hadn't met most of them, but he knew that a lot of them had entered the fight with his name on their lips, like he was some sort of patron saint of defending brave people from alien death rays.

He stopped punching, internally scolding himself for his own facetiousness. His hands were getting sore in any case, and he shook out his stinging fingers.

"Fighting some demons?" Alyx said from the doorway. He turned, startled, at her voice; he hadn't even heard her approach. She was dressed in a tank top, sweatpants, and sneakers, apparently here to keep up on her hand-to-hand combat skills, as he was.

"You could say that," he said quietly, pausing to wipe his sweaty forehead on the front of his T-shirt, "Sometimes I come here to think, too."

"Thinking is good," Alyx agreed, "but sometimes action is better." She smiled. "Need a sparring partner?"

He glanced at the punching bag, and then back at her, feeling awkward. "Alyx, I couldn't…" She put her hands on her hips, inclining her head dubiously. "I mean, I'm twice your size…" She folded her arms, pursing her lips in annoyance. It occurred to him suddenly that she didn't appear to be wearing a bra. "That is to say… I don't want you to… get. Hurt." He realized how stupid that sounded even as he said it, because she had proven herself to be quite a capable fighter.

She snorted. "Oh my god. First Barney, now you. I'm not made of porcelain, you know. I'm not gonna break." She grinned at him, assuming a fighting stance. "So let's see what you got, tough guy."

He mentally shrugged, assuming a fighting stance of his own. Her first attack came in low, and he moved by instinct alone, half-turning to defend his groin while deflecting her foot away from his abdomen. He leaned back to avoid the high punch to his face but was caught off-balance when she hooked her foot around his ankle and yanked him off his feet. He air was driven from his lungs in a sharp cough.

"Don't want me to get hurt, huh?" she asked, offering him a hand up. He grabbed her wrist and, putting his foot in her stomach, tossed her over his head. She rolled to her feet as he got up. "Not bad. Your landings need work, though."

He smiled benignly and shrugged, adjusting his glasses with a habitual poke to the bridge before assuming another ready stance again. "Again?" he asked. She grinned dangerously.

It didn't take him long to get used to her fighting rhythm. She tended to be impulsive, which was good when one was fighting a zombie and had to strike fast or die, strategy be damned. He admired her grace, her boldness, and her tenacity. She was like some jungle cat, picking her target and pouncing in as much time as it took to blink. She struck fast, aiming for vitals and pressure points to take down her opponent quickly, while he did his best to deflect or block, all the while maneuvering her to the spot he ultimately wanted.

It was then that he went on the offensive, striking with jabs and kicks at the holes he'd seen in her defenses. She laughed with delight at his newly-discovered boldness, trying to adjust her tactics to keep up and clearly loving the fresh challenge. The world entered an even sharper level of detail as he focused on his little project, to the point that he could see droplets of sweat being flung from her hair as she dodged. He never landed a blow – she was too skilled – but that was not his aim.

He felt a certain inner satisfaction when he saw that she did not even recognize his gambit until her back hit the wall of the training room and he let his momentum carry him against her. He caught her wrists as he closed, effectively pinning her.

It was a breathless moment, with her back against the wall of the training room and his body pressed against her, so close that he was able to confirm his earlier theory about her lack of bra. They were both breathing hard and soaked with sweat, their hearts pounding but not entirely from the sparring. The air between them (what little there was) was thick with anticipation and smelled of sweat and sex and science. Their faces were inches apart, and he could feel her hot breath against his lips, slightly ruffling his goatee with each exhalation.

Gordon's mind spun, like the driveshaft of a car in neutral with the gas pedal floored. He had dreamed of similar situations in recent weeks, since he had met Alyx and seen her fight. Her bravery, her strength, her beauty, her complete and utter belief that humanity would prevail in the face of overwhelming odds, inspired in him…

Oh, who was he kidding? He was completely hot for her.

He quickly decided that he was done thinking about it and leaned in, kissing her. Her lips were full and soft and slightly salty under his mouth, and the way she leaned into the kiss told him that his impulsive gambit had paid off. He closed his eyes, savoring her as his hands, completely unbidden, released her wrists and slipped around her slender waist. He felt her fingers first caressing his face, then twining into his hair in a way that gave him goosebumps. His tongue quested curiously at her teeth, and her mouth opened, admitting him to the sweet ambrosia of her mouth—

There was a discreet clearing of the throat behind him, at the doorway. He tore himself away from his taste of heaven and whipped his head around to stare, red-faced, at Barney, who was leaning against the doorframe with his arms crossed and an amused look on his face.

"Now, far be it from me to give you crap about this," Barney said, "After all, you two are consenting adults and can do whatever the hell you want – but could you at least free up the training room and go play tonsil hockey somewhere else?"

There was a long, baffled pause as Gordon tried to regain his equilibrium. He scratched his head slowly, mussing his hair even further than it already was. Behind him, Alyx burst into helpless giggles at the absurdity of the whole thing, before grabbing him by the wrist and dragging him out of the training room.

Gordon paused as he passed Barney.

"Dude, you are a complete ass, you know that?" he hissed at the former security guard.

Barney shrugged helplessly. "Hey, like her dad said, if anyone could handle her…"

Gordon glared at him, but allowed Alyx to pull him away.

Barney chuckled to himself, noticing that they were headed to Gordon's room.

"Lucky dog," he murmured.