Sol Kyung-Gu plays a staff member of the National Institute of Scientific Investigation (NISI) in South Korea. He attempts to uncover the identity of a mysterious serial killer who decapitates his victims. Ryoo Seung-Bum plays a environmentalist who holds clues to unravel the mystery.
No Mercy (Yongseoneun Eupda) is another fantastic, yet unknown for most gem from Korean cinema, and a great debut of director Hyoung-Jun Kim, strengthened by good cast of experienced actors and beautiful cinematography.Forensic pathologist Kang Min-ho (Kyung-gu Sol) is involved in investigation of a serial killer who is known for decapitating his victims. Soon police finds a suspect, odd environmental activist Lee Seong-ho (Seung-beom Ryu), who doesn't confess but clearly is somehow involved, he then starts to play a strange game with Kang Min-ho, whose daughter untimely appears to be missing.