dean seeking the story of his parents' lives, and as he's uncovering it and recounting the moments of it, it is slowly revealed that something dark has happened and has occluded his memory, so he doesn't know what transpired with their family or how everything unfolded, and little by little we realize he doesn't remember sam, and that's the truest horror of it all, because remembering sam is vital to who he is, to his heart, but it also means he has to remember his parentification and abuse, and all the brutal things that happened to both of them, and as he siphons through what's real and what may be fabricated by celestial (or possibly infernal) machinations, he realizes that essential piece is missing, and when he puts it all together, he confronts his parents about their selfishness and harm and neglect and the traumas that were endured, and sam is missing, and heaven is not what it seems at all, perhaps it was never even heaven to begin with, and dean proclaims that he and his brother deserved better, and deserved to live, and free will was never an illusion, and he is determined to break out of this trap and rescue the both of them, and the curse blocking his memory finally shatters, and he races off in the impala to figure out how to triumphantly save them and tear them off that lonely road and place them back in the lives they were finally grabbing hold of, because everything he does he does out of love, prequel/reboot hypothetical fix-it concept my beloved