Thank you to sargraf, fadagaski and meko00 for their invaluable input.
Wendigo, the second episode in the series, presents Dean Winchester in multiple functions: big brother, hunter, and hero/protector. It starts to reveal the contradictions that make up Dean: he is both believer and pragmatist, snarky and concerned, emotionally vulnerable and inaccessible. His reasons for doing things often seem to have an emotional as well as a practical reason.
Dean's concern for Sam is immediately evident as Sam awakes from a nightmare. It takes Dean a moment or two to say anything; he seems to be considering the best way to express his worry for his brother without being maudlin or pushy. Finally he settles on asking Sam if he wants to drive, making the question sound casual. (Jensen Ackles' performance is so very good in this episode, it's probably responsible for a lot of my interpretation.) When Sam responds a bit touchily, Dean immediately retreats into being terse and to talking about the job at hand.
At this point in the episode, the brothers are in complete agreement about where they're going: follow the coordinates and find Dad. Ironically it's the entrance of Haley, who is trying to save her younger sibling, that upsets this tenuous peace. Dean counters Sam's anger at allowing anything that would distract from finding their father with not only a broader view of the hunt, but a sensible suggestion: "Maybe we should know what we're walking into before we actually walk into it."
When we first meet Haley Collins, Dean's sense of connection and identification with her is immediate and strong. There's more than a slight attraction as well. Haley, like Dean, is wary, protective of her younger siblings, and terse (although she's much more direct and honest than Dean). Dean seems both admiring of her, and surprised to see so much of himself reflected back.
It's interesting that a guy who spends so much of his life hunting the supernatural is so eager for the idea that the thing they're hunting is a solid being. As Dean tells Sam, "We're talking about a creature, and it's corporeal. Which means we can kill it." For Dean, hunting is a craft, not an art. It's a calling, but he's interested in the mechanics of it, the weaponry, the visceral satisfaction of slaying an evil thing. That said, there's something that looks a lot like a
dream catcher hanging from the inside of the trunk (see an imprecise screen grab here). According to Lakota legend, the web catches, or filters out, the bad thoughts and lets through the good ones; it is used to ward off nightmares. The dream catcher goes unremarked, but it's a good bet Dean put the dream catcher there. It seems like an unusually mystical thing for him to use, except it's possibly just one more tool of the trade, like rock salt or holy water. On the other hand, it seems unlikely he's seen a dream catcher work first hand, as he has with rock salt, which makes its presence more poignant. It's a subtle reminder of Dean's worry for Sam.
When Sam and Dean argue (again) about whether to follow Haley, Dean says he knows they can't talk Haley out of going after her brother, that all they can do is "go with her and protect her and keep our eyes peeled." That's the first instance of Dean using the word "protect." There are a number of touchstone words in this episode: help, safe, worry. Dean uses the word protect (or protection) at least three times, and I didn't catch any of the other characters using it, although Sam says it once, during his nightmare.
There's also an intriguing disconnect between the understanding of Haley that Dean reveals, and his treatment of her the next time they're face to face. When Haley questions Dean's hiking attire, he walks past her with a smirk, "Oh, sweetheart, I don't do shorts." The audience and Sam get a fuller picture of who Dean is, but the other characters don't. Dean, as he often does, is deliberately playing the role people expect to see, but it's also a role Dean enjoys, the snarky, devil-may-care untouchable hero.
The tension between Dean and the older hunter/guide, Roy, seems to point towards Dean's relationship with his father. Dean's used to working with John, an authority figure who as far as Dean is concerned really does know everything. Roy, who's arrogant and unprepared for what they're about to face, frustrates Dean, and Dean finds himself in the position of protecting not only those younger than himself, but the older man as well. Throughout the episode Dean has the air of someone who thinks he's working with amateurs. Dean acts cocksure with Roy, sniping at him "Tell me, Bambi or Yogi ever hunt you back?" Roy does prevent Dean from stepping into a bear trap, a moment which emphasizes Dean's fallibility as a hero. But Roy ignores Dean's advice, and it dooms him.
As the danger increases, Dean's leader role becomes more and more evident. Even before Roy dies, Dean starts barking orders to "stay together," and Dean starts to take point instead of Roy. Oddly, he also plays peacemaker between Roy and Sam. Although Dean has the most reason to have tensions with Roy, Roy manages to tick off Sam as well, and Dean pulls his brother away, telling Sam "chill out." He's not only playing peacemaker, he's once again pulling Sam back from the edge.
When Haley confronts Dean about who he really is, Dean is unusually direct. Without verbal evasion, he tells her the truth, or at least a sliver of it. "I just figured you and me, we're in the same boat." He later adds, "this is probably the most honest I've ever been with a woman...ever." Dean asking her "are we okay?" seems unusually uncertain. My guess is that unlike most of his conquests, he actually wants her respect and trust, even if she won't go to bed with him. (It's cheating to look at Cassie and Dean's relationship in Route 666, but in retrospect, it's also possible Dean is afraid of being rejected).
Sam asks Dean "Why are we still even here?" Dean's response shows his faith in his father. He gives an impassioned statement about the importance of his father's journals: "Everything he knows about every evil thing is in here and he's passed it on to us." He also states his philosophy of the hunt: "I think [Dad] wants us to pick up where he left off. You know, saving people, hunting things. The family business." Dean has an awareness of continuity, the torch being passed from father to sons. I don't think in Wendigo Dean believes Sam is being selfish. Dean's annoyance at Sam seems to stem from concern; he's trying to give Sam a dose of perspective, to show him an up-side to their (to Dean, at least) necessary detour.
Another reveal about Dean's character is his advice to Sam to have patience and not let the anger consume him. He tells Sam "I'll tell you what else helps: killing as many evil sonsofbitches as I possibly can." Dean's statement fits with his practical approach to killing supernatural beings, and leads to speculation about Dean's relationship with anger. Perhaps he channels his frustrations into killing the things that go bump in the night.
As Dean tells the siblings about about wendigos, we also get a glimpse of one of Dean's less obvious roles: storyteller. We know Dean's a good con artist and actor, skills that in themselves are storyteller qualities. Both Dean and Sam are keepers of John's journals, and Sam often figures things out before Dean, but if Sam relies on books and papers, Dean seems to do it by memory. Dean does the telling with an almost theatrical flair, as if spinning a ghost story. Sam inserts a few details, but it's mainly Dean's story to tell. It's also Dean in the big brother role, maybe turning the wendigo background tale into a story to distract the Collinses and keep them from panic.
A role reversal occurs when the Wendigo snatches Haley and Dean, and now the younger siblings have to rescue them. Dean leaves a trail of peanut MM's for Sam to follow, which not only shows Dean's practicality in a crisis, it also hints at the rapport between the brothers, and I wonder if they've done something like that on hunts before.
When Sam finds Dean, he's half-conscious and hanging from the ceiling of the cave. Dean's response to Sam's "You okay?" is an almost impatient "Yeah." When Sam cuts Dean down, Sam again asks "Sure you're all right?" Dean replies "Yeah. Yeah. Where is it?" He can barely speak, obviously clenching his jaw against pain, yet he brushes off Sam's inquiry and immediately asks about the wendigo, back to business. It's both a coping mechanism to keep himself from falling apart and a belief that this is his duty. It's also part of Dean's archetypal, it's-only-a-scratch type hero behavior. Later as Dean puts himself in danger, running off to distract the wendigo to let the others escape, we see he's moving painfully and clutching his side. Having assessed his own injuries, Dean has decided that he can handle leading the wendigo off; I get the feeling he wouldn't have volunteered for it if he thought he wouldn't be effective. We see Sam in the protector role when the wendigo corners him and the Collinses, but it's Dean who performs the spectacular rescue in the end.
In Dean's farewell to Haley, we see more of Dean playing a role he's crafted for himself. There's something very self-conscious about Dean's smirking. He's not merely hitting on her. It seems to be a way of keeping her at arm's length emotionally. "Must you cheapen the moment?" Haley asks him, and he says emphatically, "Yeah!" But when she kisses his cheek, Dean looks utterly unsettled, and he watches her walk away with the same intensity that we've seen between them throughout the episode (in their two intense scenes, Dean always breaks the gaze first). As with so much else with Dean in this episode, there's both a practical and an emotional possible explanation. The relationship can't go anywhere, Dean has to keep moving because of the quest. So a flirtation is fine but more than that can't happen. Emotionally, when he meets a girl he feels a strong affiliation for, and genuinely likes, maybe he imagines her burning on the ceiling, and hides behind a smirk, therefore placing her safely back into the category of the one-night-stand girls that he's attracted to but doesn't feel a particular bond with.
In a final symbolic/practical gesture, Dean tosses the keys of the Impala to Sam. Symbolic because he's giving up some control. Sam saved him, it's like Dean thinks Sam has earned the right to the keys to the Impala, at least temporarily. But it's a follow-through on his earlier offer to Sam.
Most likely it's for a very practical reason: Dean's in too much pain and too tired to drive.