Not a perfect drama, but certainly a very innovative one. I'm saying again what I'd in previous episode that people need to understand that the story of this drama is set across the events taking place in the span of 24 hours and not multiple days.
Considering this drama was set across 24 hours, it's believable that why police weren't able to apprehend Si-woo.

The basic plot is that a serial killer kidnaps the daughter of Lee Ho-cheol. This killer has been living in plain sight as Ho-cheol's neighbour. What follows next is the cat and mouse chase between Ho-cheol, Kwon Si-woo (serial killer), Bae Tae-jin (assassin) and the cops.
Ho-cheol racing against the time to save his daughter from being getting killed by Si-woo.

Personally, I liked the idea of this story. It was like 24, US drama.
Yes, the execution wasn't perfect, but it wasn't that bad either. The story could've been stronger.
But what I think the biggest drawback is that there were only episodes per week. This kind of acted as "continuity-breaker"
People couldn't stay connected with the story because of the duration.
If people would binge-watch it in a go, the story would make much more sense.

The ending kind of open-ended. Most of the things were ended perfectly, but I still think there is a chance of a sequel.

Overall, the weakest drama from OCN in a long time. Nevertheless, a nice drama and full points for the experiment.
The direction was weak, as was the story, but the acting was spot-on. Lee won-keun literally gave me chills with his performance. He was very good as a serial killer. His chilly smile would send shivers down one's spine.
Nice comeback for Jin-goo after disastrous Legal High.
Ha Do-kwon nails most of his roles, and here also he was perfect.
What I rue about is that there wasn't much to do for Lim Hwa-young. She was good as a cop, but some scenes should've been added showing the mother-daughter bond, particularly at the end.

A nice 8.0/10 from me.