This was a fun episode. It knew exactly what it was trying to do, and it accomplished its goal by being really light hearted all the way through, but still touching on some more serious elements as well.

Basically, the premise is that a child star has died, and the Feds are assigned the case for some reason. Beckett and McCord come down and basically block Esposito and Ryan from investigating. Castle ends up mixed up in the case as well, since he's looking for something to get him out of the apartment and away from Pi and Alexis.
Part way through the case, a CIA agent also shows up and complicates things. Long story short, the FBI keeps blocking the NYPD from getting things done, and then the CIA does the same thing to the FBI. This silly chain of inconvenience is played for laughs, and the episode knows exactly how hokey it really is. 

Of the case, nothing much needs to be said. The child actor was working on a reunion movie from the teen show he was on when he was younger. The suspects include people working on the movie, and then a bigger plot is revealed, in which Russians are using the movie to smuggle guns into the country. (I know. What?)

Castle, Esposito, and Ryan use their usual investigative techniques to find a warehouse where the illegal merchandise is waiting. Beckett and McCord also find the location, only they use their fancy GPS tracking technology to do so. It was an in-your-face sort of comparison between the two techniques, but I think it worked okay.

In the end, they catch the bad guy - the former co-star of the victim. Most of the meat of this episode didn't come from the case, although it was decently entertaining to watch Ryan geek out over the show he used to love as a kid.

On a more serious note, this episode showcased a couple of dynamics that I thought were pretty fun to explore. For one, Castle basically has to choose between loyalty to the NYPD (Esposito and Ryan) and his fiancee. The choice would seem obvious, except for that Castle sort of agrees with the boys when it comes to the FBI's rude behavior. Nobody, including Captain Gates, is thrilled that their case is being stolen from them.

Then there's the ending of the episode, which is when things take a turn for the actually serious. In the course of the case, a young Russian woman is implicated in the crime and is in danger from her Russian mobster family. Beckett hears the CIA agent basically threatening the girl to spy on her family for them or else he'll tell them she already ratted on them and put her in a lot of danger. Beckett releases information to the press that makes this girl essentially useless to the CIA, thus saving her from her fate.

This was a good moment that cemented the fact that Beckett is still the same person she's always been. Throughout the episode, she had to toe the line and do things by the book, but in the end she does the right thing even though it breaks the rules.

Castle then gives us a squeal-worthy moment when he announces his intent to move to DC and get an apartment with Beckett. Kate looks really excited about this, and the two share a kiss. However, Castle's gesture quickly becomes obsolete after McCord comes in to announce that the FBI figured out what Beckett has done, and that she's fired.

So, yeah. Actually a pretty tense ending. I'm sort of annoyed. I didn't really like the FBI storyline particularly, but I was just starting to enjoy McCord as a character and I thought this episode did a good job of balancing things out... now I'm not really sure where they're going to go from here.

In all, this episode had a fun case of the week and a few good moments. In terms of its place alongside the rest of the season, I'm curious and a bit skeptical about what it will mean for Beckett now that she's lost her amazing life-changing career opportunity.