This is a very entertaining story with a strong setting and many shifts of tone in its collage of more or less predictable plots. Set early in the 20th Century, its hero is a disreputable private dick (Hwang Jun-Min) who only handles divorce cases, but he gets roped into a strange series of murders by a frightened if gung-ho medical student who becomes Watson to his Holmes.
What we extract from the colorful and labyrinthine plot is the same thing we get from other recent South Korean thrillers with a modern setting: a sense of pervasive corruption at all levels of society and a desire to cover up unpleasant secrets. This particular case leads to a circus and a ring of aristocrats with unsavory tastes (including a particular go-to cliché for modern thrillers), with a big chase setpiece and various vivid supporting characters along the way.
Since this narrative chooses to follow other characters’ points of view besides the detective, the audience knows certain things he doesn’t. This alienates us from playing detective along with him, but he remains the closest thing the film has to a moral center, and he’s unapologetically opportunistic and not above enhanced interrogation techniques. The ending leaves the possibility for a series.