In a semi-episodic twist, this episode details the mysterious story of Yeong-joo (played by Park Seo-yeon), a high school student who appears to have murdered her abusive father. Inspector Ryoo and his crew of fellow detectives are investigating the case as if it's a one-off event. As they see it, Yeong-joo is only relevant to the extent that she's a possible source for their trying to locate the powerful drug that's been driving the narcotics trade of the previous storyline, Bad and Crazy, Cha Hak-yeon, Han Ji-eun, Jung Sung-il-I, Kang Ae-shim, Kim Dae-gon, Kim Sae-bom, Lee Dong-wook, Park Seo-yeon, Wi Ha-joon, Yoo Seon-dong