Great episode.
The core mystery was nice and twisty. I liked how it kept transforming, eventually ending in a place totally unrelated to the bracelet. It was great that Castle finally got to say the butler did it. That really felt like something he would be dying to say.
I really liked Caskett's little handshake scene. It was cute, sort of touching and then they managed to twist into a joke. Sort of a microcosm of what makes this show so great. Oh yeah, I also love that they get ridiculously turned on by solving crimes.
The Alexis and Castle "good-bye" scene was very nicely done. The monster under the bed bit was cheesy, but, again, it's one of those things I enjoy about the Castle character.
The preview for the next episode looked good. The season has been great so far. The best part is I'm sure they can keep it up.