Not only the best, this drama doesn't have any major logical problems with its plot.

First, the chemistry between the 2 leads. It is perfectly built up alongside the plot. Their trust not instantly grew the moment they face eath other. They have to go through so many things that they can finally trust each each other. Also they're actually such adorable couple.

Second, the police's work isn't against any illogical way at all. Of course, policemen aren't perfect. But there are many dramas where the police are like a bunch of highschoolers who don't know how to conduct an investigation or even being outsmarted by ordinary citizens. In this drama, the police work according to what we expected them to do.

Third, all of the characters (especially the support roles) aren't there to be just cannon fodders. They exist with reasons. Moreover, all of the events happening in the drama can also be explained logically.

All in all, I don't have any major problems with this drama. There are only a few dramas that I gave more than 9.0 rating. This drama is one of them. Highly highly recommended.