The DNA result found on the weapon that was used to kill Kang Duk Soo confuses Moo Chi. Bong Yi joins Hong Ju’s team and starts investigating the Suseong serial murder case. With Ba Reum, Bong Yi begins to find the link between the Suseong serial murder cases and the Guryeong attempted murder case. At the same time, Moo Chi also looks into one of the inmates’ cases from Moojin Penitentiary.