After a year of trying to find a way to diffuse Castiel— made all the more difficult because they couldn’t call the one person they’d usually ask for help in a situation like this— Sam, Dean, and Bobby have finally discovered that the only way to stop him is if he makes the choice to stop himself. Sam and Bobby are sure that, after a year, the power has completely taken him over, but Dean refuses to believe this, and goes looking for him at Crowley’s old warehouse.
Dean: Hey, Cas.
Castiel: Hello, Dean. [smiles mildly] I’ve been expecting you for some time now. So you’ve come to talk me into giving up this power? Or to kill me? It’s one or the other, I’m sure.
Dean: You know, for the first time maybe…well, ever, you’re wrong. I came to talk.
Castiel: To talk? Dean, I can’t remember the last time you had anything to say to me.
Dean: I can. Remember that night when we…found out about this plan of yours, about you working with Crowley?
Castiel :Do I remember the night you trapped me in holy fire and treated me as an enemy instead of a friend? Vividly.
Dean :Did you ever wonder why, Cas? Why I cared so much more about stopping you from doing something like this, working with a demon, than I ever did with anyone else? Hell, even Bobby worked with Crowley. Did you ever wonder why it was you working with him that I hated so much?
Castiel: Because you held me to impossible standards. You—
Dean: I held you to the same standards you held me to.
Castiel: [surprised] That’s not true.
Dean: Oh, it’s not? When I wanted to say yes to Michael, stop this whole thing before it got started, if I’m remembering right, you smashed my face in an alley. But when the tables were turned and Sam was the one who wanted to say yes, when Sam thought he could brainwrestle the devil, you were down. Why was that, Cas? Because it wasn’t that you didn’t care about Sam. Was it that you hated the thought of seeing my face, and hearing my voice, but the words coming out not being from me? Was it that you hated the idea of seeing something else walking around wearing my skin? Because that’s how I’ve felt for this past year. Seeing you like this…man, do you have any idea how hard it’s been watching you walk around full of righteous crazy? You haven’t been Cas.
Castiel: I’m not Cas. Cas is gone. Cas was weak.
Dean: [shouting] And I didn’t want him to be gone! He wasn’t weak, you weren’t weak, any more than I was weak for wanting to say yes! Level with me, you didn’t want me to say yes for the same reason I didn’t want you to do this. Because I didn’t want anything bad to happen to you. I didn’t want you to stop being you, ever.
Castiel: It wasn’t for the same reason.
Dean: It was. Look me in the eye and tell me that you didn’t try to stop me because of that. Look me in the eye and tell me you didn’t try to stop me because you loved me. Because that’s why I tried to stop you. And I know you’re doing this God-complex thing now, and you probably don’t care, but whatever. You wanted me to hear you out before you did this, and now I want you to hear me out. I don’t care if it’s selfish. That’s why I tried to stop you a year ago and that’s why I’m here now. I love you. I tried to stop and I can’t. And I never told you, and I should have, so I am now.
Castiel: If you’re trying to get me to let my guard down so you can kill me—
Dean: We both know I can’t.
Castiel: If you think I’ll give up this power because you told me you love me, you’re wrong. You’ll stop, you’ll change your mind, it won’t last.
Dean: It’s lasted since I met you. It’s lasted through this year. I think that means it’ll last through anything.
Castiel: [bitterly] It didn’t last the year you were with her.
Dean: You left for Heaven! What the hell was I supposed to do?
Castiel: I only left because you didn’t want me to stay!
Dean: [shocked] …Okay. [pause] So I should have told you the truth then. And I didn’t, and that’s my fault. So I’m telling you now. I love you.
Castiel: I wish it changed anything.
Dean: So do I.
Castiel: Nothing that’s happened this year can be undone. I’ve killed, I—
Dean: I don’t care. I love you.
Castiel: Shut up! [pushes Dean away with his mind] I could shut you up; I could stop you with a thought.
Dean: Then shut me up. Stop me. Kill me. I don’t care. I love you.
Castiel: [quietly, without much conviction] I could.
Dean: [moving closer again] I know. But I still trust you. I still love you. That’s not changing, okay? Look at me. I don’t do this. I don’t do big, dramatic confessions of love. This is so beyond chick-flick, and I don’t care. I look like an idiot. It doesn’t matter. I don’t care how stupid I look or what happens. I just love you. I’m not gonna stop. The night we met, you looked me right in the eye and you told me I deserved to be saved. And now, I’m telling you. Cas, you deserve to be saved. I’m not giving up on you; you never gave up on me. I love you.
[Castiel closes his eyes, and, after a moment, sinks to his knees. Dean moves forward to catch him. Castiel seems unaware of the bright light suddenly surrounding him.]
Castiel: How do we reverse it? How do I let this go, how do I…?
Dean: [smiling] You just did.