"...se." Nathan heard just the fragment of sound, catching it just as his finger tapped the button on the MP3 player to interrupt his study mix. He looked over at his roommate, hoping to pick up some hint from context of what he'd missed, but Zachary just looked at him expectantly. He had a little crooked grin on his face, that 'I am definitely smarter than everyone else' look he sometimes got when he dropped a bit of neurology jargon into a conversation that he knew nobody else understood.
Nathan tried to pretend he didn't notice. It was usually the best way to deal with Zachary's attitude. Not that Zachary wasn't impressively smart, but there was knowing you were smart and there was thinking everyone else was stupid, and Zachary had a bad habit of losing track of the line between them. Whenever anyone pushed him on it, though, he just got defensive. It was easier to ignore the little smirk, pretend everything was fine, and ask him to repeat himself. "Hey, sorry, I di-"
It was as far as Nathan got before his mind caught up with what his senses were telling him. His hand caught his attention first-it wouldn't move. He started to gesture at Zachary, some insignificant little motion that he probably wouldn't even have consciously noticed...except for the fact that he couldn't make his hand move away from his cock. It felt like it was magnetized in place. He could move it up or down, but not away.
That shock of awareness cascaded into a chain of other sudden realizations. Nathan blushed at the sudden, awkward understanding that Zachary was smirking and staring not just at him, but at the way his hand automatically pumped up and down the shaft of his hard cock. Not just hard, he realized as he looked down. It was an angry, throbbing, purplish-red, with precum already smeared all over it like he'd been stroking himself for ages. He forced himself to stop, but he couldn't pull his hand free. And as soon as his concentration lapsed even a little, it was right back in motion again. He didn't understand how he could have missed it, but now that he noticed how turned on he was, it was difficult to think about anything else.
And he was looking at his cock. That hit his brain like an electric shock-he was looking at his cock, because he wasn't wearing any clothes. He was sitting on the couch just like he usually did when he was studying, he had his wireless earbuds in and his MP3 player on the coffee table with the rest of his stuff, but he was completely naked and sitting on a towel. He didn't remember taking off his clothes. He didn't remember masturbating. The gap in his memories seemed to suddenly yawn open wider and wider as he examined it, swallowing minutes and hours until he realized he had no idea when he stopped having a firm recollection of events.
All of this passed through his head in less than a second as "Hey, sorry, I di-" turned into, "What the fuck? What the fuck is, what the fuck what the fuck what the FUCK?" before he could even finish working his way through it all in his head. The panic he felt appeared out of nowhere, blossoming up under the arousal as he tried with increasing desperation to stop fucking his hand and realized that not only could he not control his hand, he couldn't control his cock, either. Freaking out didn't soften his erection even a little.
Zachary's smirk turned into a full grin. "You asked what I was working on," he said. "I figured I'd show you."
Nathan's stare flashed back and forth between Zachary's leering green eyes, magnified by his thick glasses, and his still-stroking fingers. "Show me?" he asked, the confusion and fear in his voice deepening as he continued to struggle for ownership of his own body and failed. "I, I what, I don't understand, show me what? Show me what?" He didn't remember asking Zachary about anything, let alone anything that could lead to this weird, fucked-up situation. He couldn't even stand up, he realized. His legs didn't want to rise from the couch any more than his hand wanted to stop pumping his cock, and it was increasingly clear that his brain didn't have a vote anymore.
"Calm down, 'dude'," Zachary said, sounding mildly irritated. It sounded so typical that Nathan was momentarily distracted from his incipient freak-out; he was used to Zachary putting little ironic quotes around 'dude', 'bro', 'man', and anything else he could think of to hint that he thought Nathan was a little too macho. Which was more amusing than anything else, usually; Nathan ran track to get him through school while he went for a degree in sociology, he wasn't exactly taking 'Rocks for Jocks' courses. But Nathan knew better than to sing the praises of social sciences in front of Zachary 'the brain is just like a computer' Halliday.
"That's better," Zachary went on. Nathan felt a muted shudder of fear as he noticed the way his panic had subsided into a glassy, helpless calm. "As I was saying, I'm showing you my research. I've been studying a lot about the way the brain processes sound-or more accurately, how it generates sound, because what we think of as 'sound' is really just a set of neural impulses produced by the auditory nerve on sensing vibrations. Sound is a purely psychological phenomenon." He snorted. "It's all in your head, 'bro'."