High school student Gi-Tae (Lee Je-Hoon) takes his own life. His father (Jo Sung-Ha) feels a heavy sense of guilt and confusion over his son's death. The father was largely absent from Gi-Tae's life. He decides to search for answers on his son's death.

Gi-Tae's father finds a picture in his son's desk drawer. The picture consists of Gi-Tae and high school friends Dong-Yoon (Seo Jun-Young) and Hee-Joon (Park Jung-Min).

Gi-Tae's father is able to locate Hee-Joon. The high school boy is evasive with answers, explaining he transferred to another school prior to Gi-Tae's death. Hee-Joon also mentions that Gi-Tae's best friend was Dong-Hoon. Gi-Tae's father thinks back to his son's funeral and recalls that Dong-Hoon never show up for his best friend's funeral. Gi-Tae's father then asks Hee-Joon to find Dong-Yoon, who has now dropped out of school completely. What happened to these three former best friends?