Ko, a corrupt detective whose mother recently died, drives away in the middle of the funeral, having been informed that his squad is being investigated by internal affairs for bribery. He crashes into a homeless man who wanders onto the road, killing him. Fearing manslaughter charges, as he is intoxicated, Ko declines to call the police, and hides the body from a passing patrol car. With the body in his trunk, he returns to the funeral and manages to seal the body into his mother’s coffin while escaping detection. A few days later, Ko purposely gets into another crash, which conceals the earlier damage and gives him a reason to visit the repair shop. To the fortune of Ko and his squad, the aforementioned investigation is cancelled by a lieutenant named Park. A Hard Day 2014 full
The next assignment of the squad happens to be the capture of a wanted murderer, Lee, revealed to be the homeless man. While searching his hide-out, the squad finds nothing significant, but they meet another police officer who is investigating a hit-and-run incident based on an anonymous tip. As it happens, the hide-out is right next to the site of the collision, and a traffic camera is nearby. The squad examines the low-quality camera footage, noting that the model of the colliding car is the same as Ko’s. Moreover, a triangulation of the homeless man’s phone, while inexact, points to an area near Ko’s mother’s grave.
It is revealed that the driver of the patrol car mentioned earlier was Park, who outranks Ko, and that he witnessed Ko’s collision, though he doesn’t know where the body was taken. Rather than formally report Ko, Park black-mails him and demands possession of the body. Ko excavates the coffin and searches Lee, wishing to understand why Lee’s body is so important, and finds Lee’s cell phone as well as bullet marks on his body – leading him to believe that Lee was already dead before Ko hit him.