Carl doesn't hear the door open, but when he turns his new roommate his hovering behind him.

"Whoa! Somebody's light on their feet," he says, rising from his desk. In future months, he'll get used to the silence of his roommate's footsteps. "You must be Sam. I'm Carl."

Sam Winchester smiles and offers his hand.

Carl's first impression is that Sam is a "gentle giant." He has a firm handshake and a shy smile. He's unusually tall, but slouches considerably. His eyes, hidden under shaggy bangs, immediately latch onto the window. Then they flit to the door. Most new students give the room a once over upon arrival, but they look for the furniture, not the escape routes.

"Welcome to Stanford. We don't get transfer students too often, so I'm sure you'll get a lot of attention."

Sam groans. "How do I avoid it?"

Avoid it? What college guy doesn't want attention? Besides, Sam is pretty good-looking. He'll get plenty of interested girls.

"Listen, there's a party tonight downstairs. I'll introduce you to some cool people."

"Thanks, but, um, I'd like to unpack." Sam drops an army-green duffel on his bed.

"Is that all you have?"

"Uh, yeah." He pauses and casts his eyes up to gauge Carl's reaction. "I travel light."

Light? He can't have more than a change of clothes and a toothbrush in there!

"Where are your textbooks?"

"I don't have them yet. The, uh, college is covering those fees."

Textbook cost coverage only goes to kids with full rides. Then it clicks in Carl's head – the scholarship, the lack of belongings. This guy must be dirt poor. So he stops asking questions.

Damn, Sam Winchester must be a genius to get a full ride to Stanford. Carl can't help but feel curious towards his roommate.

Over the semester, Carl discovers more small quirks of Sam's.

For one, there's the salt. Every time it's Sam's week to grocery shop, he returns with two pounds of the stuff. At first, Carl thought the guy just really liked salty foods, but in fact, Sam barely uses any of it for food. One day, Carl finally asks about the salt on the windowsill.

"Force of habit," comes the reply. That's Sam's answer to everything.

The gun under his pillow? Force of habit.

The jug of water with a rosary floating in it? Force of habit.

The penknife always in his pocket? Force of habit.

Carl's decided that Sam had a rough childhood. It doesn't explain everything, but it covers most of the bases, including Sam's reluctance to discuss his family. Carl has a few pictures up of his parents and younger sisters, but Sam has nothing. Whenever anybody asks him a personal question, he diverts it by changing the subject. It's a careful, subtle avoidance, something no one would ever notice. He manages to hide his secrets from everybody. But Carl lives with him, so Carl sees everything.

Still, it took him three months to find the long, curved knife on the top shelf in the closet.

Another theory is that Sam is a serial killer. Carl thinks he should be scared, with all the guns and knives. He's only stumbled across a few, but they've been expertly hidden, which makes him wonder just how many more there are stashed around the dorm. And Sam is tall, too, and well-muscled, although he hides it beneath baggy jeans and thick jackets. Carl's never seen the guy through a punch, though. And Sam is studious. Like, stay-at-home-on-a-Friday studious. Carl heard from another mutual friend that Sam is also fluent in Latin. Weird, maybe, but not the traits of a serial killer. Not much of a threat. For most of the year, Carl is certain Sam wouldn't hurt a fly.

That theory falls apart on April 3.

They're just leaving a frat party with some friends. Sam makes friends easily, because he's incredibly polite and friendly. Girls tend to be interested in him too. But he refuses to let anyone in. Carl doesn't know a thing about the guy, beyond his own observations. Nobody knows where he's from or what he wants to do with his life. Sure, he's got friends, but not close ones.

Anyway, the party is just ending when it happens. Sam, Carl, and a handful of people are standing together outside the frat house when one of the crossfaded frat boys approaches a girl. It's the typical frat-party harassment which everyone ignores because it's nearly unavoidable. But unlike everyone else, Sam intervenes.

At first it's just a few polite words to the senior, gently pushing him away from the girl. The guy is a second-string football player and nobody crosses him. In fact, his expression when approached by the shy, bookish transfer student is almost comical. Almost, because Carl knows Sam is about to get his ass kicked.

The guy tries to use his height to intimidate Sam, but it turns out Sam has an inch on him.

"What are you trying to say?"

Sam meets his gaze evenly. "You shouldn't talk to girls that way, that's all."

Carl tugs at his roommate's arm, but is surprised to find Sam as unmovable as stone. "C'mon, dude, just let it go."

Sam relaxes his stance. "You're right." Then, to the girl, "You okay?"

When she mumbles a yes, he starts to turn his back. But he's only three steps away when Carl sees the senior start to swing his fist.

The next moment feels as though it's in slow motion, cliché as it sounds. In reality, it only takes a second for the football player to extend his arm. And in that second, Sam leans half a foot to the side and twists around, almost as if he has a Spidey-sense.

The senior trips forward. There are only a few people around, but all eyes are locked on the fight. Carl knows there's no stopping it now. He just hopes Sam can do more than dodge.

Speaking of which, what was that? It took a moment to sink in, but now Carl's realizing that Sam knows how to fight. He moved with lightning speed, dodging a blow Carl barely saw coming. And Sam had his back turned.

Then it just gets weirder.

The senior continues to swing, fists flailing. None of his punches make contact. Sam dodges with expert agility, never returning a blow.

"I don't want to fight you," he says. Hell, he's not even out of breath! "I was just intervening. You can't treat people like that, even when you're drunk." He's lecturing a guy while dodging punches. Carl has never seen anything like this, and he doubts he ever will again.

"C'mon!" pants the football player. "Why don't you fight back? Fight back, dammit!"

Sam hesitates for a second, ducks under a blow, then shrugs. "All right."

All it takes is one blow. One karate chop to the neck and the frat boy goes down.

Carl thinks he hears a girl at the back whisper, "Is he… dead?" No, only unconscious. Carl doesn't know a lot about fighting, but he's pretty sure something like that, no matter how powerful, wouldn't kill. Still, he's definitely seeing his roommate in a new light. For a moment there's a gleam in Sam's eyes, almost as if he's high off the adrenaline rush. That look terrifies Carl. It makes him worry that Sam liked that. Sam's never gotten into drugs or alcohol while at Stanford, but now Carl's wondering if he's addicted to danger.

Then the moment passes, and Sam is back to his usual self. He apologizes profusely to the girl for blowing up the argument into a fight. She just nods and forgives, looking both shocked and turned on by Sam.

There are too many disconnected pieces of his story. Carl doesn't understand Sam Winchester, and he doesn't think he ever will.

One more piece falls into place just before finals.

Sam and Carl are taking a joint study break, splitting a beer and discussing summer plans.

"Do you think you'll get a summer job?"

Sam laughs bitterly. "Are you kidding me? I have to."

Carl ducks his head, embarrassed. He'd forgotten momentarily that Sam is a scholarship student. College doesn't cover summertime fees. Sam will have to struggle through the next few months.

"Okay. What do you think you'll do?"

Sam shrugs. "Maybe car mechanics." Then, almost to himself, he adds, "Dean would love that."

Carl jumps on the unfamiliar name. "Who's Dean?"

Sam looks up, eyes wide. "Dean's my brother." He says it as if it's the most obvious thing in the world. Above all else, Dean is Sam's brother. Carl is almost embarrassed for not knowing. But then, he didn't even know Sam had a brother.

"Your-" Mind reeling, he has to sit down on the edge of his bed. "You have a brother named Dean."

Sam stiffens. "Yeah, I, uh, I guess I don't mention him often."

"More like ever!" He doesn't want to pry, but just this one name tells Carl more about his roommate than he's learned in months. "Listen, you never talk about your family. It's about time you gave me some straight-up answers. What's he like?"

Sam looks down at the beer in his hands, frowns. "He's a soldier. Brave, protective. He doesn't let a lot of people in."

"Sounds like you, then." He means it light-heartedly, but Sam just shakes his head.

"No, Dean's- Dean's nothing like me." He doesn't elaborate.

"Do you get along with him?"

Sam shrugs. "We used to. He took care of me."

"And now?"

Sam clears his throat, downs the rest of his beer. "Since when is this your business?"

"That's what I'm talking about!" Carl points an accusing finger. "You always divert the conversation when it gets too personal. I'm sick and tired of it, Sam. I just want to get to know you."

That makes him laugh. "No, you don't."

"There you go. I get it, you've got a dark, angsty past. Violent, I assume. And your family is involved. I'm not blind."

Sam doesn't correct anything, so Carl forges ahead.

"Look, I'm really not trying to pry. But your brother, Dean. He's a soldier, you said? Did he ever, you know… bully you?"

Sam stands abruptly, rising to his full height, and for a moment Carl thinks he's gone too far. "No! Of course not! Jesus, where do you get that idea?"

Carl backs down. He remembers what Sam did to that football player, with just one hit. "Sorry, I just, you've never even mentioned him."

It takes a moment, but Sam relaxes his stance. "Look, I just… I haven't really talked to Dean in a couple of years."

Oh. Sure, Carl knew family was a sore subject, but he didn't realize the depth of it. "And your parents?"

"The night I left for Stanford, my father told me I shouldn't come back."

Carl hates the way Sam says that. Carl may not have a perfect family, but at least he has one. He has a place to go for holidays. Sam, apparently, has nothing.

"But Dean, Dean's nothing like that, okay?" His eyes are wide, insistent.

"Okay, chill, I wasn't saying-"

"Yeah, you were. Carl, you're a nice guy, you really are. But just… stop asking questions, okay?"

"What if I don't?" His pulse quickens, thinking of the gun under Sam's pillow. Things would never go that far, would they?

Sam follows Carl's glance to the pillow and rolls his eyes. "Jesus, I'm not going to shoot you. It's just some things are better left forgotten." When Carl says nothing, Sam rises and returns to his desk. "Okay, I've got more studying to do."

Carl requests a single-bed dorm for the next year.

He hears stories about Sam Winchester, about a girlfriend and a fire, but he's learned better than to pry. He doesn't ask questions. Maybe Sam is a serial killer, maybe just a quiet kid with a fucked up childhood. Carl's finally content with never learning the truth. He's lucky to have met Sam Winchester. The unsolvable mystery, hidden behind mumbles, baggy clothes, and salt.