Yook Dong-sik (Yoon Shi-yoon), an analyst who works at Daehan Securities, has a timid personality. He can't even get angry at the people who look down upon him. One day, shortly after failing on his attempt of suicide, he witnesses a murder. He unintentionally picks up a diary belonging to the murderer, on which was written the log of his murders. He flees with the diary, but he is accidentally hit by Police Officer Shim Bo-kyung's (Jung In-sun) patrol car which causes him to suffer fromretrograde amnesia. Due to the diary in his possession, Dong-sik mistakenly believes he is a psychopath. Since that moment, his behavior started to change. Bo-kyung, who got involved with Dong-sik, decides to catch the serial killer.
Meanwhile, Seo In-woo (Park Sung-hoon), the director and son of the chairman of Daehan Securities where Dong-sik works, turns out to be the heartless psychopath serial killer. He loses his diary when his 6th victim, a homeless old man tossed his diary away. He feels insecure ever since, He is obsessed and in love with DongSik .[4]
Yoon Shi-yoon as Yook Dong-sik, a timid and pushover man who works as a clerk at Daehan Securities. His weak personality begins to change when he perceives himself as a killer.[5]
Jung In-sun as Shim Bo-kyung, an officer in a patrol station.[6]
Park Sung-hoon as Seo In-woo, the real psychopathic serial killer who is also the director of Daehan Securities where Dong-sik works at.[5]
Hwang Geum-byul as Yook Ji-yeon, Dong-sik's older sister.
Kim Gyul as Jo Yong-gu, Dong-sik's brother-in-law.[7]
Jung Su-bin as Yook Dong-chan, Dong-sik's younger half-brother.[8]
So Hee-jung as Na In-hye, Dong-sik's step-mother, Dong-chan's mother.
Heo Sung-tae as Jang Chil-sung, a gangster who lives at Unit 708. He later addresses Dong-sik as his 'Big Boss' after mistakenly believes him to be a serial killer.
In the table above, theblue numbers represent the lowest ratings and thered numbers represent the highest ratings.
This series aired on a cable channel/pay TV which normally has a relatively smaller audience compared to free-to-air TV/public broadcasters (KBS,SBS,MBC andEBS).
