Short version of this review: A beautifully set up and well paced P2K4 (pawn to King4) episode where the characters are moved around the board like chess pieces, setting up what is to come. I loved it, but, as my reviews have indicated, I am a huge fan of the series (and the production team) and am watching it in sequence, one at a time. This episode is NOT for newbies, and this NOT the way to introduce yourself to BANSHEE if you have never seen it before.
Longer version: The use of dual arcs in modern TV drama has in fact been around for a long time but, most experts agree, was taken to new levels in the nineties by none other than Joss Whedon who, the theory goes, revolutionized modern TV by his use of the short and long arc in primetime TV.
The short arc is the immediate action in the episode. In a CSI for example, the short arc is catching the bad guy. The long arc is all the stuff going on between the characters. The kind of writing that used to appear only in "soap operas." In the 90s Whedon (yes, the same man who has recently revived the Marvel catalog, and both WRITES and DIRECTS the Avengers movies) did an interview where he said that, in any series he is involved in, he writes the long arc at least 4 years into the future, whether the series lasts that long ... or not.
The long arc predominates in this episode and one suspects the writers have studied their Whedon very well. If you are a fan of this great series, you will get it. If you are not, you will wonder what the fuss is about. (I could explain it to you ... but then I would have to kill you.) This remains one of the most interesting and risk-taking series ever produced.