That episode had me rolling. I thought it was all kinds of fun. The out-of-his-depth police chief, Beckett's desperation to keep their relationship secret, Castle's unwillingness to let the mystery go (and then Beckett doing the same thing later), Ryan and Esposito digging into Beckett's private life because they just have to have some kind of case to solve... I enjoyed it from start to finish.
I especially liked that Ryan didn't reveal the secret to Esposito in the end. He really is a softie.