Dean and Crowley hunting together! Sam and Cas bromance in the bunker! A dream come true! Let's dive right in to the plot.

Dean is on his own, being sad, when Crowley approaches him and asks him for help in tracking down the First Blade, which is apparently a super fancy knife that can kill Knights of Hell, and thus take care of Abaddon. So, using John Winchester's journal, the two of them find an old hunting friend of John's named Tara. She has most of the ingredients for a locator spell, and Crowley is able to supply the last piece. Crowley and Dean track down the location where the First Blade is supposed to be. Instead, they find... Cain. Crowley is terrified of him, but Dean insists that they can't leave until they have the Blade. Cain shares his story with Dean and Crowley - he was one of the first demons. He killed his brother Abel because Lucifer was going to corrupt him, and he couldn't bear to see his brother taken to Hell like that. So, Cain took his place. He trained the Knights of Hell. Then, he fell in love with a woman, but Abaddon and the other Knights of Hell murdered her. He killed them all, but left Abaddon alive because Colette begged him to stop the killing, as her last wish just before she died. So, Cain ends up being sort of allied to Dean and Crowley's purposes, because he does want revenge on Abaddon.

Cain reveals that the Mark of Cain can be passed on to someone else, but only if they are worthy of such a gift/curse. Dean is one such worthy person. Ignoring warnings from Cain that the mark comes with a terrible price, Dean accepts the Mark. Demons, who followed Crowley and Dean after killing Tara, show up at Cain's house. He tells Crowley and Dean to run. Dean then learns that Crowley had manipulated these events from the beginning, and Crowley doesn't seem at all perturbed that Tara lost her life in the process. Although Dean is furious, he realizes he still needs Crowley, since the actual First Blade is hidden at the bottom of the ocean, and he needs Crowley to fetch it.

While all of this is going on, Cas is back at the bunker continuing to heal Sam. As he does so, he finds a bit of Gadreel's grace is still inside of Sam. Cas says that it might be useful as a locator to find Gadreel. The only trouble is, it's going to be very painful and potentially life-threatening to extract the grace from Sam. Sam tells Cas to go for it, stating his willingness to die to put things right. Cas pushes Sam right to the limit, but when it comes down to it, he can't bring himself to let Sam die. He tells Sam that he understands what it feels like to be Sam, since he's the only person who's screwed up worse than Sam has. Sam gratefully hugs Cas. Cas then tells Sam that he wants to go and find Metatron, because he's determined to fix what he broke.

Alrighty! I'll start with my complaints, because I just wouldn't be me if I didn't have any. The main one was Dean's reactions to Crowley. For one thing, why didn't he just stab the guy on sight at the start of the episode? Obviously from a story point of view it would be stupid to kill Crowley off right now, but from a character point of view, why didn't Dean stab first and ask questions later? Later, when Dean finds out that Crowley had arranged this whole thing and that he had been trying to find Cain in the first place, Dean's reaction was a bit less intense than one might have hoped. Sure, he hits Crowley, but Crowley's actions had caused the death of Tara. You would think perhaps a stronger reaction would be necessary.

Speaking of Tara, here comes my other complaint. There were only two major female characters in this episode. Tara, and Colette. Each of them is dead by the conclusion of the episode, and each is basically only there as a plot convenience. Colette is there to be Cain's reason for angsting away. Tara is there to help them find the Blade, and she also mentions that she and John Winchester had a thing at one point. This seems totally unreasonable to me. Like, it would be fine if it weren't for the fact that there's such a pattern of this crap in Supernatural. Did Tara really need to die? Could she not have lived on to guest star once or twice more, at least? She reminded me a bit of Ellen, in a good way. Acidic, hard to talk to, but ultimately a good and helpful person. Why kill her off? Colette was painfully bland. She was basically just "generic pretty lady who has to die to fuel some man-pain." Seriously? Ugh.

But now that I've complained, on to the good stuff!

Crowley and Dean! I know I complained about some of Dean's reactions, but other than that this element of the episode was really good. Crowley may be the only character on the whole freakin' show who normally pays more attention to Sam than to Dean, so it was an interesting idea to look at Crowley and Dean's relationship. I think the writing for Crowley is awesome. And the acting, too, for that matter. I think what's so perfect is the way that they're toeing the line between Crowley's bad side and his budding humanity. He doesn't seem at all bothered that Tara had to die for his plan to work, but at the same time he tries to buck up Dean's self-confidence, and he genuinely does seem to care about the Winchesters. What a deliciously complex character (now if only we could pull this off with a woman. Ahem).

Cain. The addition of Cain to the show's mythology was a very good call. All of the parallels between Cain and Dean have already been pointed out, but in particular think about how sad it is that Cain killed his brother Abel to spare his soul. We already know Dean would do the same - he shoved a soul back into Sam once, even though everyone warned him it would probably kill him. I think this ultimately shows that while Dean is selfish as hell, his ultimate happiness involves Sam being happy. If Dean has to die to accomplish that, then so be it. But if Sam has to die? No way. I really liked the stuff with Dean and Cain, because it reinforced again how damaged Dean is. Also, I love it when big players on the mythological scene know about the Winchesters. I get a kick out of the fact that Sam and Dean Winchester are basically household names for all the angels, demons, and other assorted monsters in the world.

Sam and Cas! These scenes in the bunker were amazing. Another under-appreciated relationship on this show is of course the one between Sam and Cas. Whenever we get hints of it, I'm so excited, but usually of course Dean's relationship with Cas and his relationship with Sam overshadow their relationship to one another. Here, we got to shine a great big spotlight on it. Yay!

I'm not even going to break it down and talk about the Sam and Cas stuff in too much detail. It was all brilliant. The peanut butter and jelly sandwich was brilliant, the moment when Cas says "you and Dean chose each other..." wow. Also, the speech Cas makes at the end about messing up and understanding what that means. And he apologizes for all of the mistakes he makes, and Sam forgives him! And there's a hug! And we also see, quite disturbingly, that Sam still seems quite willing to die. It's like his life doesn't mean anything to him anymore. And really, who can blame him. I've got to say, my favorite funny moment in the episode was when Sam says to Cas: "You're a terrible liar," and Cas replies, quite offended: "That is not true! I once deceived and betrayed both you and your brother." That had me laughing pretty hard.

I'm doing a pretty good job of keeping these Supernatural reviews at a reasonable length! That's all I've got for this one!