The narrative begins with a daylight bank heist directed remotely by James from a high rooftop. The surveillance team combs through thousands of hours of CCTV footage to discover an anomaly: an anchor operative nicknamed 'Water Hippopotamus'. By staking out his routine, the squad traces the broader organization.
James operates under a shadowy broker called the 'Teacher' (Kim Byung-ok). When James demands his retirement following a securities robbery, the Teacher dispatches assassins to kill him. James brutally eliminates the hitmen and murders the Teacher with his own weapon before attempting to flee the country.
The tension peaks when Detective Squirrel spots James on the street and tails him into an alley without backup. James identifies the tail and fatally stabs Squirrel with a pen/knife, devastating the unit and pausing the operation. Refusing defeat, Yoon-joo reconstructs her memory of Seoul's subway passages, re-identifies James, and guides Chief Hwang into a subterranean railway tunnel. Cornered on the tracks, James attempts to draw his gun but is shot dead by Hwang and SWAT operatives. The film closes with the healed unit deploying to an airport to track a new international target (Simon Yam).