Towards the end of book six, Rachel's boyfriend dies, and her memory of the event id wiped clean (so that she doesn't go after the guy without a plan). The result is that she's know idea who killed her love interest. In response, she spends most of the book trying to work out who might do such a thing (and why). At the same time, she's asked by the police to help investigate a Banshee (who can kill you by removing your emotions) who they suspect of attempting to kill a copper.
The book is a better read than the authors' 2 previous outings with Morgan. There are a couple of reasons for this. First there's more story to the book (rather than talk and love interest), which is always a good thing. Second there's less love interest. Don't get me wrong, I understand that women can get as turned on by the physical as guys, but I don't think that many guys like to read about another guy's glistening pecs or pert butt if I'm honest (I'm a bit ho hum about girls being described similarly too before anyone says anything). It's part of the reason I walked away from the series a while
Incidentally, I wouldn't necessarily recommend starting here in the series. If you think the story sounds interesting, I'd start with book 1.