"The Bottle Imp" brings Grimm back into familiar territory - almost too familiar, really, since this type of procedural episode has been downplayed the entire season. Even when Grimm has gone back to its formula of introducing a new Wesen with a bad temper, the show has tried to incorporate some sort of new event in the serial drama started in the season finale of season 1. Unfortunately, this back-to-basics approach that "The Bottle Imp" takes means that the show leaves out much of what has been making this season a delight to watch.
That's mostly because Grimm has really been digging into a lot of different long-running dilemmas, and so for "The Bottle Imp" to mostly leave any mention of those out is negligent. While I do like to see the new Wesen, I'm more interested in how they relate to the developments that have shaped Nick's life - Juliette's loss of memory, Hank's new involvement in Grimm life, Monroe and Rosalee's relationship.
Rosalee is out, because Bree Turner is pregnant and they can't really explain that away on the show. But that doesn't mean that Monroe can't craft a relationship with Hank, or that the plotlines about the royals should be thrown away to make room for a tedious episode about an apparent kidnapping and murder.
It's not that the plot for "The Bottle Imp" is bad - if this were season 1, Grimm might have been able to get away with this. But we've seen stories like this done on the show before, and the impact of the reveal of the daughter being the murderer is lessened because from Grimm, we've come to expect these kinds of things. If it were a straightforward case, it still wouldn't work too well, so at least the writers do what they can with this episode.
It's just unfortunate that the show didn't decide to carry on more with its building conflicts. Sure, Juliette seems to be falling for Cpt. Renard, and he in return, but that's been happening the entire season, and just because it's explicitly expressed doesn't make it a new development.
Hopefully Grimm gets back to exploring the new avenues of Nick's life now that being a Grimm has messed it all up. That's when the show works best - these one-shot episodes might prolong the series, but after a while they begin to feel like bottled plotlines released whenever the show needs a filler episode.