The first half is what the drama should've been and the second half is what the drama shouldn't have become. The start was decent enough with a compelling concept and characters, however, everything began to crumble down after the first half. The pace significantly slowed down, an overwhelming amount of repetition and flashbacks was shoved in, the mystery was over at that point, the cat and mouse chase became boring and there was a general decrease in the collective IQ of the masses. Nonetheless, the story itself was weak and didn't explore any interesting ideas. The whole thing was infested with plot holes even after excluding all the supernatural elements. The inclusion of romance was a hit or miss at times. I'm disappointed that Park Won Sang didn't have a bigger role in the drama.