Opening scenes in "Death by Hanging" consists of a death chamber ready for an execution given to the viewer in a documentary style. A Korean man, known as "R," is being hung for his crimes, although he remains alive after the hanging. Now the plot delves into the existing law; that a hanging shall not proceed without acknowledgment of the crime or the punishment for that crime.
The hangmen decide the only solution is to convince R he has committed the crime by reminding him of the allegations and the evidence surrounding the case.
The officials begin a campaign to recreate the crime scene, where R is convicted of raping a woman. When this plot fails, they move forward into recreation of his childhood and remind him of the stereo-typical Korean known to some of the Japanese population. Frustrated with the lack of sparking any sort of memory in R, they visit another crime scene where R has been known to commit undesirable acts. The abandoned high school doesn't bring back his memory either, however, in an attempt to perform the reenactment one of the officials attacks and shoots a girl.
A woman appears at the death chamber, claiming to be R's sister. She tells R that all of his crimes are not crimes at all, but were conducted against a Japanese enemy, which is justified by Korean nationalism.
After she finds she can't convince him of the background to his criminal activity, she is hanged. Officials hold a party to celebrate the hanging of the woman, and open up to reveal their own violent pasts. R is present at the "tell-all" gathering. The prosecutor in R's case opens the door to allow R the chance to run free but he is stopped by an intense light from outside the doors.
R finally admits his guilt in the crimes. He tells the officers that if they kill him by hanging him, they are murderers themselves. In the second hanging, viewers are left with a decision to make on their own; was he hung or was the empty noose hanging under the gallows an indication that he was set free?