Character Arc
Jang Nan-gam is the detective at the heart of the investigation, a stubborn and methodical officer who refuses to accept that a string of seemingly unrelated cases is coincidental. Where colleagues are ready to close files, he keeps pulling at loose threads, and his persistence gradually draws him toward Lee Tang. He functions as the relentless engine of the cat-and-mouse pursuit that structures the series.
His characterization avoids the cliche of the flawless investigator. He is dogged, a little obsessive, and willing to bend procedure when his instincts tell him something is wrong, which puts him in conflict with the system around him. As the chase intensifies, the show uses Jang to probe questions of justice and process, contrasting his faith in the rule of law against the rough, extrajudicial logic that Lee Tang seems to embody.
Son Suk-ku plays Jang Nan-gam with a dry intensity and understated humor, grounding the thriller in a recognizably human investigator rather than a superhuman one. His pursuit becomes as much a moral reckoning as a manhunt, and the tension between his determination and the unsettling possibility that the victims were themselves guilty gives his arc its weight.