The Gangster, The Cop, The - Devil

The investigation leads them through the gritty neon streets of Cheonan. The gangster’s henchmen and the cop’s unit play a dangerous game of cat-and-mouse with K.

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

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 The investigation leads them through the gritty neon

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: Intel: Tae-suk provides police data and forensic tools

They find K’s weapon—a specific type of knife—and track his stolen vehicle.

At the trial, K almost walks free due to a lack of physical evidence. In a final masterstroke, Dong-soo turns himself in to the police. Since he is the only survivor of K's attacks, his testimony is the "smoking gun."