I'll try to post these every other week day (Mon-Wed-Fri), but I make no guarantees. Sometimes there will be more than one cap for a beginning or ending of an episode. I'm also using my capper's discretion - meaning I'm choosing the most aesthetically pleasing image that we see first or last not always literally the first or last things we see. I'll explain this as we go along.
:: Click on images for the HQ versions ::
6.20 Beginning: The episode begins with Cas praying to God and recalls witnessing the beginnings of man on Earth and then how he and the Winchesters averted the apocalypse.
Castiel: "And, of course, I remember the most remarkable event - remarkable because it never came to pass. It was averted by two boys, an old drunk and a fallen angel. The grand story. And we ripped up the ending and the rules...And destiny...leaving nothing but freedom and choice. Which is all well and good, except... Well, what if I've made the wrong choice? How am I supposed to know? I'm getting ahead of myself. Let me tell you my story. Let me tell you everything."
We first see one of the boys with Dean driving in the Impala alone before Cas pops in briefly to chat.
6.20 Ending: By episode's end, the boys find out that Cas has been working with Crowley (who is very much still alive) to open Purgatory, and that Cas also raised Sam from Lucifer's cage. With all trust lost as far as Sam & Bobby are concerned, Cas tries to talk to Dean, but Dean warns Cas that if he tries to open Purgatory he'll have to stop him.
Cas, still praying to God asks for a sign or he will do what he must.