Season 1

Flailing at life, Lee Tang panics after he kills a man after work. Soon, Jang Nan-gam is on the case — discovering a disturbing truth about the victim.

A mysterious woman approaches Tang, claiming to know his secret and begins to blackmail him. The weight of his actions starts taking a mental toll.

Nan-gam struggles to find clear answers as he investigates the latest deaths. After connecting with an enigmatic figure, Tang decides to turn himself in.

Wondering if the same killer is behind all the murders, Nan-gam probes Roh Bin for clues, leading to an unlikely partnership between the two.

As Nan-gam notices a clear pattern among the recent murders, he searches for Tang — unaware of another mysterious man who is doing the same.

In his search for Tang, Song Chon confronts Bin — who desperately turns to Nan-gam for help. But Tang agrees to meet with Chon, who has a proposition.

Nan-gam comes face to face with Chon, who recognizes him from the past. As Bin and Tang plan their final escape, Bin receives a menacing phone call.

The endgame to the chase leads to a final fight — and it's everyone versus Chon. In the process, Nan-gam finally learns the truth about his father.