The Gangster, The Cop, The Devil -

Jung Tae-suk is a hot-headed detective convinced that a string of recent "accidental" murders are the work of a single serial killer. His superiors ignore him, but he realizes Dong-soo is the only living witness to the murderer. The two men strike a deal:

Dong-soo provides the manpower and underworld intel. Intel: Tae-suk provides police data and forensic tools. The Gangster, The Cop, The Devil

As they close in, K realizes he is being hunted by both sides and begins to enjoy the challenge, intentionally leaving clues to bait his pursuers. The Climax Jung Tae-suk is a hot-headed detective convinced that

The 2019 South Korean action-thriller centers on an unlikely alliance between a brutal crime boss and a rogue detective to hunt down a nihilistic serial killer. The Inciting Incident Intel: Tae-suk provides police data and forensic tools

K is sentenced to death and sent to prison. In the final scene, Dong-soo is sent to the same prison. As he enters the showers where K is hiding, Dong-soo smiles and says, "I told you there are three men who will risk their lives to catch you." If you'd like to dive deeper into this world: of the characters' moral gray areas Comparisons to the real-life "Cheonan serial killer" case