OK, let's get this acknowledgement out of the way: yes, it was awesome for "Firefly" fans to see Nathan Fillion and Adam Baldwin reunited on this week's episode of "Castle". The scene where Fillion punched Baldwin made me giddy, and then sad that we got only one season of "Firefly" and one movie of "Serenity".
But aside from that bit of fan-service, this wasn't a particularly good episode of "Castle".
The case of the week was even less important than usual, because it was really just used as a vehicle to contrast Baldwin's corrupt, mildly insane cop "Slaughter" (subtle naming there, writers) with Beckett's style of police work, which itself was just a way to show Castle all the many ways he prefers Beckett.
I enjoy "Castle" more than typical procedural because of the cast of characters and how they mesh with each other, and this episode really minimized the impact of that. Sure, there were some solid moments -- Ryan, in particular, had a couple good one-liners -- but so much time was spent with Slaughter, who was really one-dimensional.
Mostly, though, my biggest complaint with the episode was with the Alexis story. Now, in the past, "Castle" has often used the home life of Richard Castle to serve as a metaphor or guide for what's going on at the station, but never has it been more hammered home than it was on Monday. The final scene, with Alexis unsure how she felt about being accepted by Stanford after she'd been rejected, may as well have had a big flashing "THIS IS A METAPHOR FOR CASTLE'S FEELINGS ABOUT BECKETT" sign on it. It was embarrassingly simplistic for a show that usually gives its audience a little more credit.