Warning: Spoiler Warning
I'm so very, very glad that what we had here wasn't what the preview seemed to be showing us for this episode. From the preview, what it looked like what we were going to have was Castle being believed to be the killer ... yet again ... and the gang thinking that he was really the one who had done those crazy things ... again. The probably that I had with that idea was the fact that maybe the gang may have not known for sure about him in the beginning, whether or not he would be willing or able to do something truly heinous to another human being, but they've gotten to know him over the past 4+ seasons, and they should know him better than that now ... they should know at this point, no matter what his flaws me be, he is not the kind of person who would harm another human being like that ... not for kicks. The only thing that could really make him harm someone else is if he was trying to protect himself or others (and it's never going to be something that he just does for kicks, the way a serial killer does).
As amusing as it was when the boys were trying to figure out who it was that Beckett was seeing, and to watch Beckett and Castle freak out over the fact that they might have been on the right track about what was really going on ... I'm glad that both of the boys and Lanie now also know (along with Martha and Alexis) that Castle and Beckett are together. As much of a pain in the ass as I'm sure that it would be to keep that sort of thing away from the captain (since the captain is likely to try to keep them apart when it comes to questions of ethics, at the very least), the fact that they don't have to keep this away from the people that they are the closest to (and who are most in their lives) is probably a relief; it's no fun to have to keep things away from the people that you most care about in the world, esepcially when it's something so important to you as the person that you are seeing. If you've found love, having to keep that thing under wraps has got to be toxic to you as a person, as well as to the both of you as a couple.
Speaking of them being together: when Beckett was talking to Lanie about the whole thing ... yes, I was glad that she was clear through that whole thing that she believed in him and that she didn't at all think that he had anything to do with what the evidence was making it look like he had done ... the fact that in the midst of that saying that she knew that murder wasn't like him, that she started saying how egoistical and self-involved that he was ... that's the sort of thing that bugs the hell out of me when it comes to Beckett. She may love him, but she has never been at all forgiving when it comes to him; she always has seemed to focus on the bad parts of his character and used it to try to make him feel like there is something wrong with him, and I've never liked that about her. I've had someone do that to me (where they keep pointing out things that they don't like, in what seems like a constant effort to make me feel bad about myself, and that isn't contusive to a loving and healthy relationship. As much as he loves her right now, I have a feeling that if she continues to pick at things about him, he's going to start feeling like he isn't good enough (not just for her, but for anyone); even with the healthy self-esteem that he has at this point, it's going to wear him down after a while).
I also don't see why, after all was said and done, she refused to believe his instincts when it came to what 3XK was trying to do. After all, that's the whole reason why she was willing to keep him on in the first place, and why she went to bat for him with the new captain: he has great instincts, and can sometimes see things that the others miss, since he is so good at looking outside the box (and he doesn't have the cop mentality, where everything has to be a certain way to work). And espeically after 3XK said straight out that the only way that he could go back to killing was to pretend that he was dead for a while, and that they had taken that ability from him (and how pissed he seemed to be about that). I don't see why Beckett is unwilling to trust his instincts about this, when she's willing to trust his instincts about everything else. Maybe it's more convenient for her to think that he's gone? That's only thing that I can think of for why she would try to handwave the entire thing to make it seem like it was something other than what it actually was.