Yeah, I did like Castle admitting that he doesn't really believe in the inane supernatural theories he expounds but is just messing with Beckett. I just wish they'd established that two years ago so I wouldn't have been annoyed so often at Castle being written like a gullible imbecile.
But how many more times are they going to go to the "murder involving a fringe subculture based on something from fantasy/sci-fi/folklore" well? What's next, a mummy's-curse murder involving mummification fetishists? A club of people who dress up in animatronic dinosaur suits, making Castle think a murderous velociraptor has come through a time rift? Electrocution by Zeus's lightning bolt revealing a cult of Hellenistic neo-pagans? It's like they write themselves!
I'm not surprised that Alexis decided to stay in NYC for college; I've been expecting for years that they'd take that route, for which there's plenty of precedent (like, say, Smallville
's Clark and Lana deciding to attend the state university that conveniently got retconned into existence right outside town, or Wesley Crusher missing multiple chances to get into Starfleet Academy so that he had to study aboard ship). But now that it's happened, I'm not sure how authentic it feels from a character standpoint, given how much time they've spent establishing her eagerness to move on and challenge herself. I mean, it kinda works that it's her devotion to her family that keeps her around, but I wish they'd done more in earlier episodes to lay the groundwork for that, so that it didn't feel so much like a copout when it was sprung on us here.