From the writer of Kingdom, Kim Eun-hee, it starts slowly but pulls you in with tight writing, weaving small cases together into a larger picture. The story spans across timelines, changing the past and the present with ease and coherence. Very rarely do you see timetravel shows which have a coherent storyline. Christopher Nolan should watch this show, how to build a story from the middle to the start and the end without confusing the viewer.
The crimes are compassionately portrayed, making it a chilling watch. Especially so because three of the four big cases the trio solve are based on true crimes, aaand the fictional fourth one was the least gruesome.