The humoristic aspect is tuned up in this epi, as Castle's first ex-wife and Alexis' mother shows up. Meredith is a totally crazy, compulsive shopper/actress who just does what she wants when she wants to. One of those babbling, domineering types of Hollywood girls. Castle has a "sleepover" with her and seems to be having a great time until she announces she's going to permanently move to NY. Castle's expression at that moment, simply priceless.
The case is about African immigrants in NY and a series of ritualistic, Voudon murders. The settings for the killings revolve around a street of shops run by immigrants, one of which sells imitation designer bags. Meredith proves helpful when she recognizes the imitation and eventually leads the team to the killer.
Beckett/Castle chemistry keeps evolving, and Beckett seems to hold her own pretty well against his charm, teasing and picking on him every chance she gets. There was a tinge of jealousy there, when she found out he slept with his ex. Also, the secondary characters, the other cops in the team, the Chief and so on, are being given more screen time which is definitely good. Another great one!