I thought this episode lacked character, and flirted too much with B-movie horror. The doctor being responsible was a nice twist, but at what point did this doctor decide to change into completely different black clothing whenever the body transformed?
Grounding Manny just played a trope we've seen far too many times in too many different programs and films.
There were a few episodes in the middle of this season where Constantine had character-driven human stories behind them, and they worked well. But Zed is still more walking plot device than a character with drives, motivation, and conflict. The episode with Chas's past was great because it made him human - but now he's passive again, and exists to slightly forward the plot. John Constantine is a great character, but he needs a cast around him to bring out conflict between them - they've done that nicely with some of the Newcastle characters from the comics - so why can't the writers do the same with Zed and Chas?
I'd love to see Constantine succeed, but as I've said before, this series needs to distinguish itself in its own way, and stop trying to be a shadow of Supernatural.
We've had some really good episodes, but the show is still inconsistent, lacking character development arcs, and most of all, lacking a background story - 12 episodes in and "the rising darkness" is nothing more than an empty catchphrase.