A Hard Day

Ko, a corrupt detective, drives away from the funeral intoxicated after colliding with a homeless man. He decides not to involve the police and hides the body in his car trunk. The act sets off a chain of moral breaches that will haunt him as the case unfolds.

Back at the funeral, Ko stashes the corpse inside his mother's coffin to avoid detection. Later, he discovers the homeless man's phone still inside the coffin with the body, deepening the mystery and tying the man to him.

A few days pass and the Internal Affairs investigation into Ko's team is quietly closed by Lt. Park. The resolution feels suspicious to those who suspect corruption remains. The case seems to end without accountability.

The squad is reassigned to track down the wanted killer Lee, whom Ko recognizes as the homeless man he killed. The pursuit tightens the pressure on Ko and his colleagues as they begin the search. The new target shifts the team's focus.

While investigating Lee's hideout, they encounter another officer handling a hit-and-run case. They learn Lee's location sits beside the crash site and is visible from a traffic camera, suggesting a link to Ko.

A phone triangulation places Lee's last activity near Ko's mother's grave, deepening the mystery and hinting at a personal connection. The finding unsettles Ko as the past intrudes on the present case.

The patrol driver who passed Ko on the fatal day is revealed to be Park, the lieutenant who quietly closed the IA investigation. He uses that knowledge to coerce Ko for control of the corpse and the case, heightening the stakes for both men.

Ko digs up the coffin and finds Lee's body bullet-riddled. Lee's phone receives a call from a fellow criminal, revealing that Park stole cocaine and hid profits in a private vault; Lee had stolen the key and fled. Park had shot Lee during the pursuit that coincided with Ko's accident.

Ko returns to the grave to locate the key but is abruptly arrested by a subordinate who tails him after noticing the car damage from the Lee incident. The arrest marks a new danger line as Park's influence looms.

Park uses a crane to drop a shipping container onto the subordinate's car, killing him. The act demonstrates Park's willingness to destroy anyone who threatens his control of the case.

Ko contemplates going public with Park's crimes and even considers surrender, but Park counters by threatening Ko’s sister and daughter to enforce silence.

In a desperate move, Ko steals an explosive from the police basement, implants it into Lee's body, and hands the corpse to Park. He detonates the charge, blowing Park's van off a bridge into a lake.

Ko returns to his apartment to report everything, but Park survives the blast and stages a confrontation. In the chaotic moment, Park accidentally shoots himself while trying to dislodge a revolver from a toppled bookshelf.

With reputations at stake, a cover-up takes hold and Ko decides to resign. He uses Lee's body to infiltrate Park's private vault, preparing to expose the truth.

While infiltrating the vault, Ko discovers an enormous cache of cash—far more than he imagined—forcing him to confront the true costs of power, profit, and the price of truth. The find signals a new moral crossroad as Ko weighs exposing Park against the danger to his own life.