Sad Secret

A brutal serial murder case, all the evidence points to the murderer who died 10 years ago. A murder occurred in the bathroom in the middle of the night. Dong Geun, a detective from the crime team, found fragments of a diary with a date ten years ago on the body - "This too shall pass." "Dongan" learned that the note as the only evidence of the incident was part of the diary of "Youngxun" who served in the army with the victim, and that he had committed suicide 10 years ago. "Donggun" believed that the suspect was "Sung Hyun", a pharmaceutical company executive and the man behind the military bullying at the time. However, because he also died in the same serial murder case, the case gradually fell into a maze. At the same time, during the in-depth investigation of the case, "Dong Geun" discovered that "Young Xun" was his friend from his student days. The case entered a new situation with the forgotten memory...