This week's episode featured the the extent and depths of Sam's addiction and the riff it created between both good and evil as well as Sam and Dean.
Dean and Bobby did an intervention to get Sam to go cold turkey on the demon blood addiction. While in the panic room, Sam is visited by several hallucinated demons: Alistair, little Sam, Mary, and Dean. These hallucinogenic visits may seem as an effect of the detox, but they are actually Sam's insight and views of himself and how he believes others perceive him. However, Alistair just seems to be the beginning of the demon blood detox, his presence is just a foreshadowing of the rest of Sam's night spent locked up.
The next visit is from little Sam. Little Sam just seems to rant and complain about how Sam has turned out. Little Sam argues how the older version of himself is just finding excuses to continue what he is doing. With this visit from the younger Sam, we see how Sam had wanted to turn out: innocent, normal, untouched by the unnatural. The younger Sam is just seen as the argument Sam had originally set up for turning away from the supernatural and hunting lifestyle.
In a later visit, Mary appears to Sam. Originally, Sam believes that this "visit" is just another part of himself arguing against his new found turn against humanity. However, this version of Mary argues for Sam saying that Sam is justified in doing these actions. Mary explains that Sam is stronger than Dean and should therefore continue on his merry little way. With the way Sam does not seem skeptical of her presence, Mary portrays the stance Sam has taken in this grand fight.
Lastly, "Dean" is seen hurting Sam, putting him down, expressing Sam's deepest fears coming from his beloved brother. This Dean is calling Sam all the things he has never wanted to hear especially from someone he loved so dear.
While Sam is being visited by his inner demons, Dean struggles with everything going wrong with Sam. He and Bobby go over the possibility of their intervention of killing Sam. While Bobby is obviously softening out over locking Sam up, Dean is definitely refusing to let his brother turn to the dark side. Dean is blatantly refusing to give into Sam's need for demon blood, and he willingly agrees to become a warrior of God.
Towards the end, Sam is released from his prison by none other than Castiel and tries to hide from Dean while getting in contact Ruby for another hit of the mojo juice.
In the end, the brothers brawl out in the honeymoon suite of some motel after Dean had tried to kill Ruby. The tension and emotional struggles between the once close brothers lead to them going at each other like a bunch of rabid dogs.
This episode, the second-to-last of the season officially shows the sides the brothers have taken in the apocalypse. Sam blindly follows Ruby believing he is fighting for the good of all mankind but is actually fighting for the title of Top Dog. Dean refusing to let his brother turn into something inhuman willingly agrees to fight on the behalf of good and God in order to preserve the sanctity of his brother's once good nature and that of mankind.
This episode finally showcased the turmoil that had abounded over the course of the season. We finally understand Sam's drive to pursue and carry on with Ruby: to take out Lilith. He argues earlier in the episode that he persist because of vengeance and justice although Azazel was the one that originally caused the problems. We come to see that Sam is driven to sacrifice himself in order to protect the world from going through what his family had gone through.
From the other side, we understand that Dean is driven by the need to protect his brother by whatever means necessary. Dean obviously does not want Hell on earth, but he also puts the welfare of those he loves above all else.
Ultimately, we have yet to see how everything that has transpired will play out in the end. Will Lilith