Sam Winchester: What's the catch? What do you want?
Arthur Ketch: Protection. From Asmodeus.
Dean Winchester: The one you're working for?
Arthur Ketch: Was working for. When he finds out that I stole his prize milk cow, well, I imagine that he'll hunt me to the ends of the Earth. So... this is the only safe place I know.
Sam Winchester: What? Do you think you're just gonna move in?
Arthur Ketch: Dibs on the top bunk?
(Ketch traps Sam, Dean and Toni in the bunker...)
Arthur Ketch: Your bunker is an excellent fortress. An even better tomb. So we've rejiggered the locks, we've shut off the water, and once we leave, the pumps that bring in the air shall reverse. Your oxygen should be gone in... two days, maybe three. You dying in here, it's almost... poetic, hmm?
Mary Winchester: Did you kill him?
Arthur Ketch: Mick was weak. He wasn't one of us. When will you realize that we will do whatever it takes to rid this world of the things that go bump in the night? Something that people like Mick and your sons are incapable of. I've been cleaning up after them for months. I took care of those federal agents they stupidly allowed to live. I killed a psychic girl they thought was... human. Honestly, they're damn sloppy.
Mary Winchester: I think you mean... decent.
Arthur Ketch: It's the end for the American Hunters. Their time has passed.
Arthur Ketch: Let me just say that the Men of Letters is an excellent fit for someone with our... inclinations.
Dean Winchester: "Our"? As in you and me?
Arthur Ketch: You're a killer, Dean Winchester, and so am I. And if we go too long without something to track or trap or punch or gut, well, things get a bit ugly. Don't they?