Indexing: Reflections (Indexing Series) - Seanan McGuire
This is one is hard to think about as an individual episode.  There's some plot advancement, yes.  But mostly this is about the team getting some new intel, evaluating it, and then coming up with a plan to get more information -- there are some unorthodox moves required to obtain this more, but if they're going to get anywhere towards capturing Elise before more lives are lost, they're going to have to make them.
 
The new information they are given is huge.  It's not unexpected for the reader, and you could make the case that Henry should've been expecting it.  But it's more than believable that she wouldn't have.  
 
Yes, this installment is mostly about investigation, and not busting heads, or messing with narrative incursions, or anything.  So it's hard to discuss -- but it is really well executed, what the reader and Henry learn is interesting and thought-provoking.  Not only about the case they're working on, but we get a better understanding (or at least the beginning of a better understanding) of how the whole Fairy Tale narrative functions.  
 
There's suspense, there's Sloane being Sloane, there's a cliffhanger ending.  Not easy to write about, but easy enough to read and start waiting on the next chapter -- maybe more urgently than I'm used to.
Source: http://irresponsiblereader.com/2015/09/24/indexing-reflections-episode-4-by-seanan-mcguire