Literally the police version of Stranger. If Stranger was about prosecutors investigating higher up corruption in the prosecution office, WATCHER is about the Corruption Investigation Team of four people investigating corrupt police officers who not only take bribes but also harm others, which most likely also involve corrupt prosecutors in some cases. They are highly character-centric than being more plot-centric which explains that you may easily get lost if you don't pay careful attention to many people's names and the complex nature/motivations of their greyish character. It can be slightly difficult to follow, but the psychological pay-off is extremely high if you bear with it.

I have to agree that way the story was presented to us was a bit messy. They started off with a murder of a young child's mother to a traffic violation case to a harming of police officer on-duty, to misuse of the firearm by a police officer to organ trafficking to bribery ledger involving higher-ups of public officials and a conglomerate chairman, to an illegal drug distribution network involving corrupt officers and finally the implied future investigation of powerful politicians and business people. However, this drama is in no way procedural, and the sub crime-cases are only introduced to question the true morality of some characters or bring in new characters to add to the bigger investigation trails. In this way, the transition of one case to another is quite smooth, but I see some real problems with the execution, or more precisely the way the dialogues were written to help the viewers connect the threads along their investigation trails. E.g. there are multiple instances in the show where it is not very clear how Do Chi Gwang makes the investigative deduction to implicate the higher-ups in some cases. As I observe this, the problem here does not necessarily lie in the way the whole puzzle is brought together to create a cohesive story, rather the way small details and threads are supposedly connected (or rather, told) to reduce plot holes.

My point here is that a corruption-investigation series is bound to be heavily character-centric which may explain why some people are voicing dissatisfaction over the (unnecessarily) convoluted way of the story being told. Instead, I believe making it confusing and going round in circles is likely the most plausible way to tell a story of this genre in a way that makes it episodically engaging. Thus the path the writers took should not be deemed unnecessary, rather a logical one.

Other than the weakness in the way small threads are being somewhat loosely connected to one another, I do find that the pacing of this drama is A REAL PROBLEM. I watched this drama in parts initially only for Seo Kang Joon, and only managed to finish this in entirety after working out a way to increase the playback speed, LOL. So if you have been looking for that magic tool, install Video Speed Controller on your Google Chrome extension. You're welcome.

Aside from this, I do have to say that I am very invested in all the lead characters in the show. I came here mainly for Seo Kang Joon and Kim Hyun Joo, and must say they totally nailed their characters! Kim Young Goon is a tortured character who's also a bit naive but is plain good-natured. It's amazing to see his portrayal of emotional breakdowns and rage when facing the confusion of not being able to trust anyone around him, most especially his own father. Han Tae Joo's character is a selfish one, who only cares about achieving her goals and is always ready to switch sides as long as the choices she makes brings her closer to goal for revenge. Jo Soo Yeon and Hong Jae Shik are interesting characters to look for as well, and they really do add intricate nuances to an otherwise a very dry, corruption investigation series. Do Chi Gwang is the anti-hero in this drama, which is an interesting deviation from Hwang Shi Mok in Stranger who is a straight arrow and only pursues justice and upholds integrity in his choices. Jang Hae Ryong and Deputy Commissioner Park were also the interesting ones, and I am satisfied with the plot twists they gave us in the final two episodes. In fact, compared to Stranger, I am much more invested in the most recurring characters in this drama because the way all these complex characters are written is just exceptional, and is truly the biggest strength/stand-out of this drama for me.

They also concluded this drama nicely while also hinting away at the possibility of a second season. In fact, I am eagerly waiting for the day it comes, because the upgrade to the investigation trail this time would be to investigate corrupt politicians, business people and high-ranked public officials which would make it even more interesting, like the anticipation that builds for Stranger 2. When that happens, I do hope that the writer/director managed to secure the same lead casts because they have successfully built the momentum and the right anticipation for this first season, and the way the story was written is so expendable that it's only up to the writer's skills to give that to us.

If not for some of the missed executions, MDL rating for this drama should be as high as Stranger. Enjoy your watch!

Bonus: My ranking of corruption-investigation or psychological thriller series:
1. Doctor Prisoner (10)
2. Confession (9.5)
3. WATCHER (9.0)
4. Stranger (8.5)
5. Trap (8.0)