This drama goes through essentially 3 different stages so it's hard to talk about it as a whole. The first part is the classic murder mystery with a serial killer who seems to be able to do the impossible. It's pretty interesting and I liked how the story was evolving case by case. After about a third of the drama, the story changes and it becomes very fractured. Essentially it's like the table was flipped and now the pieces are all scattered. Characters get moved around and the status quo is broken in order to have some of the characters discover things on their own. Eventually they come all together for the last third of the story in a somewhat solid resolution. The last episode has some issues that trip it up and logically there were different ways for the story to unfold in the finale. Overall I would say that the first half is pretty interesting, second half also has some good plot reveals and twists, and the third half barely is able to make it all wrap up. My biggest critique is that there weren't palpable stakes. The actions of any of the villains were always against a third party or another villain. Very rarely were they actually acting against the main characters and there were very few moments where I felt there was real danger.

Another thing was that I just finished Kill It which had some very similar themes to this drama. That was a mistake in my opinion as I started getting details from both dramas mixed up.

Surprisingly I would say this is one of Nam Goong Min's weaker acting performances. There were moments where he shine or was given room to actually perform. But the moments where he was acting smarter than everyone else started to get boring for me. Seolhyun wasn't amazing but she gave a decent performance. Nothing to noteworthy besides Lee Chung Ha as I thought she has some really unique character traits in the first half of the drama. It got kinda lost as the story started centering mainly around Nam Goong Min's character.

Overall, solid watch and a good drama. Things could have been different or better in my opinion. If you want something that has a little bit more of a punch to it, dramas like Stranger are far superior in mystery and stakes.