A/N: Hey, this is my first (and probably only) Grey's Anatomy fic! I decided I needed to write it or die trying, aiming more for the former option, of course. Enjoy!

Unwritten

It must have been an unwritten law, developed somewhere ages ago, that those things, about which a mother was sure to nag her only son, would come back to bite him in the ass when he didn't bother to listen. At least, in Derek's life, such a law seemed to reign, and he would have turned the irony into a joke, to win Mark over with humor, if he hadn't presently been paralyzed with fear.

"There's a storm coming," Carolyn had said. "You shouldn't be alone when there's a storm coming." She had given him an irksome, all-knowing smile and had added, "We both know how easily you scare."

"I won't be alone, Mom. I'll be with Mark." And Mark will protect me, he had thought to himself. Of course, he hadn't announced this detail aloud because it wasn't necessarily true.

The Sloan boy, while something of a friend to the sole Shepherd son, definitely wouldn't have been spending the evening with Derek if he had had any say in the matter. It was more a twist of fate (and of manipulative parents, who were taking Derek's sisters to a Broadway musical while they were all in town) that was placing them together.

"And what if the power goes down while we're away?" Carolyn had probed, seeming even more worried by her son's faith in the irresponsible Mark.

"It won't, Mom."

And, thanks to the aforementioned law, of course, Derek found himself sitting in pitch blackness, trying to breathe normally so as not to alert Mark to his inner terror.

Why, oh why, had he agreed to Mark's movie choice? Watching a not so fourteen-year-old-friendly slasher film, filled with blood and guts, exposed brains (the selling point), a skillful application of creepiness, and enough surprises to have Derek on the edge of his seat even before the rain pelting the windows had knocked out the lights--successfully ending the video while the serial killer was still on the loose (If anyone asked, neither of the boys screamed.)--had definitely not been his smartest move.

He would have been better off enduring show tunes and destroying his already disgraceful reputation. Then, he might not have had to explain why he was nearly shaking with panic to anyone, let alone the macho guy he sometimes referred to as his best friend.

"You okay, Shepherd?" Mark asked, more teasing than concerned.

Derek wished his voice box would function so he could say something--anything to prove his non-fear, but was he okay? He was distinctly aware of the individual drops of rain that rammed against the roof, walls, doors--of the howling wind and rolling thunder outside, of the suddenly very bright lightning that didn't penetrate the thick curtains in the living room but reflected menacingly off the tiles in the kitchen. He wasn't used to the antiqued creaking of the expensive Sloan estate, and he desperately wished he could see Mark's face, even if it was smirking at his expense. Yeah, that probably meant he was losing it.

"Shepherd?" Mark sounded a little less taunting this time, most likely wondering if the geeky boy on the other side of the couch had died of a heart attack.

Derek squinted into the darkness. "Wh-where are you?" he stuttered after a moment, pulse racing as he realized just how debilitating being completely blind was.

"Uh, I'm where I was before the lights went out." Mark said it like it was obvious, and Derek wondered if he, superior as he was, could see through the lightlessness. "Why? Where are you?" Evidently not.

"Still right here." Derek didn't like the way silence stretched on when he couldn't watch Mark's reaction, when he couldn't really pinpoint the other boy's location based on breaths that were a lot calmer than his loud and choppy ones. "Do . . . do you mind if I . . . uh . . ." He was already extending an arm across the couch, suddenly regretting that he hadn't plopped down right next to Mark. Mark jumped and let out an unmanly squeak of alarm when Derek's hand connected with his shoulder. "That's me," Derek muttered, slightly embarrassed for the both of them. "I just . . . You sounded far away."

"It's not a big couch," Mark shot back dryly, purposely deepening his voice to make up for his previous exclamation.

"Yeah, you weren't that far," Derek agreed, slowly removing his hand, not really reassured.

"Wait."

Derek's eyebrows rose when he felt warm fingers gripping his own, but he was reluctant to pull away. The contact was comforting, in a distinctly uncomfortable way. Derek swallowed nervously as he let his palm move against Mark's, sliding so that they cupped together easily.

Mark didn't say anything, but Derek was sure that if they were at all similar, he was blushing, too. He chewed the inside of his lip and settled back into the cushions of the couch, careful not to move too much and disrupt his and Mark's handhol--He didn't let the word finish in his brain because he was pretty sure there were unwritten laws about two boys holding hands, too.

Mark took a breath before speaking, and Derek unconsciously stared at the space where he thought his face might have been. "Is this weird?" he questioned, for once not cocky and decisive.

"Yes." Derek wished he had lied as he felt Mark's hand breaking free. "But, it's not, uh, bad," he added hurriedly, tightening his fingers and scooting just the tiniest bit closer when a particularly loud clap of thunder echoed overhead.

"Oh." Mark didn't protest, but he didn't return the squeeze. "Listen, Derek . . ." He shifted and his knee bumped against Derek's. "You're my friend; right?"

"Yeah . . ." Where was Mark going with this? And did he really have to discuss their tentative friendship while they were holding hands, alone, in the middle of a dark living room?

"Okay. Good." Mark relaxed somewhat but didn't continue.

"Uh, you're my friend, too; right?" Derek asked because he knew the conversation hadn't really ended.

"Sure," Mark offered, tone already less vulnerable than before. For some reason, Derek felt like he had missed an important opening, but he didn't know how to find it again.

Other than the drone of the storm outside and the resulting groans of the house, there were no sounds to distract the boys from the tension between them as they sat together quietly, hands clasped between them, a solid point of relief for them both.

Derek's breaths weren't as harsh now that he didn't feel so alone, so he could hear the unsteady but soft whispers of air passing through Mark's li--On second thought, that probably wasn't an anatomical area he should have been visualizing at that moment--Or ever! Another unwritten rule made itself known in Derek's head, and he was quickly focused on studying, instead, the hand in his.

Mark's palm wasn't sweaty, Derek noticed first, which was convenient because he hated when he dated girls with clammy hands, like Becky Dittmer, whom he had once taken to a middle school dance. Mark's hand wasn't soft, either, like a girl's would have been. It was calloused on the underside, from playing sports and climbing trees, and along the outside of his forefinger, Derek traced with his thumb a scabbed-over scratch from an everyday accident that Mark might have exaggerated into a drawn-out tale of adventure, under other circumstances.

Derek felt, rather than heard, Mark's breath hitch, and he looked up almost guiltily.

"What're you doing?" Mark asked lowly, and Derek wasn't sure what his dropped voice implied.

He didn't have an answer, really, but he knew well enough to pull his hand back to himself; handholding definitely hadn't been a good idea, like so many other choices he had made that evening. "Uh, sorry," he murmured when his arm was safely returned to his side of the couch.

Mark sighed, and Derek imagined he might have been frowning. "For what?"

"For . . ." Derek hadn't expected that question in response to his apology, so he didn't reply for some time, thinking hard before answering. "For our parents forcing you to hang out with me tonight," he finally decided, waiting a long moment for Mark to comment, but Mark didn't speak; Derek couldn't even hear him breathing anymore. "I mean, I'm sure you had a date planned or something, and I'm not really the kind of person you would normally spend time with, if you had a choice . . ." His continuation yielded nothing, and Derek wondered if maybe Mark had left the room without him noticing. "Mark?"

"They didn't have to force me," Mark declared suddenly, and he sounded a lot closer than before; in fact, Derek could feel the heat radiating off the other boy's body. "I like hanging out with you."

Derek resisted the urge to move away and the even stronger one to reach out and touch Mark (just to find out where he was, of course) and stared harder into the nothingness around him. "Oh."

"We're friends, Derek. I told you that already," Mark went on, tone all but emotionless.

"I . . . I thought you meant we were . . . you know--just . . . fair-weather friends," Derek admitted, and his words seemed meek, even to his own ears.

"Fair-weather . . . What?" Mark snorted mockingly. "You're such a nerd, man . . . But listen, if you wanna talk about the weather, what I know is that even though it's storming, I wouldn't want anyone else here right now."

Now, Derek was frowning, and, for lack of anything else to say, he repeated, "Oh." He didn't have much practice with dating and hitting on girls, but to him, Mark's remark had definitely sounded like a line.

"So . . ." Had Mark wanted more of a response? He cleared his throat awkwardly. "Anyway, I should go find some flashlights or something."

Mark was already rising off the couch when Derek reached out to grab him because he would rather have endured the blackness than been left alone for any amount of time. "Don't go," he hissed, cheeks flushing so warm, he was surprised Mark couldn't see them glowing.

Mark turned around, and Derek realized he had caught hold of the hem of his T-shirt, the color of which he couldn't remember and certainly couldn't see. "Shepherd--"

A monstrous crack of thunder shook the house, and Mark threw himself back onto the couch thoughtlessly, obviously afraid in spite of himself. His body collided with Derek's without warning, Derek found himself almost laughing at the situation as limbs tangled and before discomfort started to set in.

If Mark was embarrassed, he wouldn't let Derek know it. "Sorry. I tripped," he lied, mouth somewhere near Derek's ear.

The moist breath that displaced the hair on Derek's neck caused his eyes to widen, and he froze, mid-detangling. "S'okay," he whispered, not capable of doing much else without his voice cracking.

Mark didn't move either, and Derek sensed that he was thinking, determining what to do next; he just wished he knew what options were being considered.

Mark's breathing became shallow, and Derek distinctly heard a gulp over the screams of the weather outside. "Hey, Der . . ." Mark hadn't called him that before. "Don't be scared."

"Of the storm . . . or you?" Derek had the chance to joke before he was stunned into silence by the surprisingly soft lips that met the corner of his mouth.

"Me," Mark breathed, redirecting his aim so he connected with Derek's lips head-on, one hand making its way into the thinner boy's curly hair as he pressed against him a little more forcefully.

Derek didn't react much at first, though he had to admit it felt nice. It was just that unwritten law thing again, distracting him from the fact that Mark was really good at ki--Somebody had to have made a rule about not making out with your best friend; right?

But if it's not written . . . Whatever the law was, they didn't bother obeying it.

A/N: Review if you like.