Jack: What is it like, Dean, when you die?

Dean: You tell me, you’re the one who keeps making pit stops to hell and back.

Jack: No, it’s nothing like that. There’s nothing at the end, just…darkness.

Dean: Jack, considering the alternative, I wish you were right.

Jack and Dean are fighting some serious threats. They end up cornered in an abandoned warehouse waiting for whatever it is to come and get them, not sure if they’ll survive. 

This causes them to muse over their different experiences with death and beyond, because one of the most interesting things about Supernatural and Torchwood are its different conceptions of the after life.