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The worst is a visit from hallucinatory Dean himself, while Sam is chained to the bed (which is what happens when demon detox causes seizures and being flung five feet up and dragged across the walls). It starts off sympathetic, and we think he's the real Dean. But it gets darker -- you're not drinking demon blood for a good cause. You're doing it because you want to feel strong, invincible, "a big bad wolf in a world of little pigs." But you're a monster, Sam, hallucinatory Dean says.

Figment Dean: Sam, you're a monster! And I tried so hard to pretend we were brothers, that you weren't one of the filthy things that we hunt. We're not even the same species! You're nothing to me!

Sam pleads with Dean to take it back, but Dean disappears. It wasn't real, but the scars remain.

Those who wait
It's not much better for Dean and Bobby. Sure, they're not going through the demon DTs, but they can hear every scream and shriek and plea from Sam echoing up the stairs. They're in their own hell waiting for Sam to recover -- if he recovers at all.

Dean goes to Castiel, who remains cold and aloof. Yeah, Sam may be able to destroy Lilith, but only if he consumes enough demon blood to become something irredeemable himself. But…

Castiel: there's no reason this would have to come to pass, Dean. We believe it's you Dean, not your brother. The only question for us is whether you're willing to accept it. Stand up and accept your role. You are the one who will stop it.
Dean: If I do this, Sammy doesn't have to?
Castiel: If it gives you comfort to see it that way.
Dean: You're a dick these days.[Pause] Fine, I'm in.

And that’s what it takes to get Dean to “give [himself] over wholly to the service of god and his angels.”

Bobby is incredulous that Dean agreed to that, and he makes his displeasure known. But what else could Dean do? Bobby is also wondering whether this demon detox is a good idea. First, maybe they should be using Sam to prevent the apocalypse. Second, the detox is killing him, and if they don't give Sam more blood, he may not survive. Dean refuses. If Sam dies, at least he dies human.

Betrayal
And here's where things take a turn: Castiel uses his angel mojo to set Sam free. Gah! Why? Bobby finds Sam outside and tries to take him back in with the help of a shotgun, but Sam knows Bobby won't shoot. So Sam knocks Bobby out with the shotgun butt (Ah! Sam! Hurt not The Bobby, for The Bobby is Awesome!). And now the chase is on.

Sam gets back with Ruby, who gives him his fix, then tells him he's going to need more than she can give. She's also got intel: The last seal can only be broken by Lucifer's first, the first human corrupted into a demon. Sam assumes that's Lilith, but we're not so sure. Also, Ruby has a lead on Lilith's "personal chef" -- a demon who kidnaps newborn babies. Urg.

Meanwhile, Anna confronts Castiel about letting Sam go. I was following orders, he says. Anna is incredulous, but then she's incarcerated -- two more angels come and take her to the celestial pokey.

Dean tracks Sam down, and they try to talk. Dean wants to kill Ruby for what she did to Sam, but Sam won't allow it. I need her to help me kill Lilith! And here's where things go straight to hell:

Sam: Maybe one day you'll understand. I'm the only one who can do this, Dean.
Dean: No. You're not the one who's going to do this.
Sam: Right, I forgot, the angels think it's you.
Dean: You don't think I can?
Sam: No, you can't. You're not strong enough.
Dean: And who the hell are you?
Sam: I'm being practical here. I'm doing what needs to be done.
Dean: Yeah, you're not going to do a single damn thing.
Sam: Stop bossing me around, Dean! Look, my whole life you take the wheel, you call the shots, and I trust you because you are my brother. And now, I'm asking you, for once, trust me.
Dean: No. You don't know what you're doing, Sam.
Sam: Yes, I do!
Dean: Then that's worse!
Sam: Why?
Dean: Because it's not something that you're doing, it's what you are! It means...
Sam: What? Say it!
Dean: It means you're a monster.

And there it is -- Sam's worst fear, made flesh. Dean's whole life feeling not good enough boiling out when Sam suggested -- with the best of motives -- that he wasn't up to the challenge. And because no one can push your buttons like family, that's was enough to send them over the edge. The boys fight, brutally, and for once, Sam gets the upper hand. He chokes Dean -- doubtless thinking it's about time Dean got choked for a change! -- then relents.

Sam: You don't know me! You never did. And you never will.
Dean: You walk out that door, don't you ever come back!