Where was my Winchester Bro hug?! I want it! I demand it! All I can say is, I want some angst and guilt from Dean in the next episode. It's necessary. But I should slow down and write out the plot first, yeah?
We see Sam dressed up as a doctor, procuring blessed blood to use in curing Dean. He injects Dean with blood in the bunker, but Dean is very resistant to being cured. He seems to be in a lot of pain as he's being cured, and he uses every trick in the book to get Sam to stop. He tells Sam that he might be killing his own big brother, and when that doesn't work, he tells Sam that he knows what he did when he was searching for him.
Turns out, Sam set up the crossroads deal with Lester, so that he could use Lester to track down Dean and Crowley. He never intended for Lester to truly sell his soul, but that's what happened. Dean gloatingly tells Sam that he killed Lester himself. Dean also says that he left Sam for a reason - he's tired of having to save him. Dean's mother would still be alive if it weren't for Sam. Sam tries not to let this stuff get to him. He continues injecting Dean with the blood. Sam goes into Dean's room in the bunker and looks at signs of his old life with Dean. When he comes back down to continue the cure, he sees that Dean has escaped from his bonds.
Meanwhile, Cas and Hannah are heading towards the bunker to help Sam out, but Cas is getting weaker and weaker because of his failing grace. On the way, Cas is sure to tell Hannah that they need to keep their priorities straight - getting to Sam and Dean has to be their focus, and there can be no distractions. Particularly not distractions of the "I have feelings for you" variety. When they stop for gas, they run into Adina, one of the angels who refused to go back to Heaven. She is out for revenge, because Cas killed her friend. Adina beats up Cas and threatens to kill Hannah.