This is my first post to this forum, there hasn't been much happening, and I don't want to start on a negative note. So rather than dwelling on how appropriately "Headache" was titled, I'll talk about what I used to like about the show.
After an awkward start trying to play on specific fairy tales, it got to be a metaphorical treatment of how a police department deals with a minority community. This issue has been huge news lately, so Grimm was well-positioned. The police department of mythical Portland deals with the issue far better, under more difficult circumstances, than most real big-city police departments have. Nick is trying to move away from traditional hostilities between the Grimms and the Wesen and was making some headway.
What happened next looks like a pattern that's occurred with many good shows. Some moron of a studio executive must have demanded more violence to goose the ratings. So the writers lifted the plot of the Star Trek (original series) episode "Wolf in the Fold," bringing in notions which have nothing to do with the established mythos and looking for every opportunity to make it as gross as possible.
I'm hoping they'll get back on track next season. There was a very interesting comment that Renard made recently, something to the effect that most crime everywhere is Wesen-related. It doesn't seem likely that it's just Portland and Vienna that are full of Wesen; they must be lurking in society's shadows everywhere, and perhaps not just in the shadows. There are all kinds of things that could be done with the premise.