Yoo Hee is a young, up-and-coming criminal profiler whose father is suddenly murdered as part of a series of unexpected killings. Following the death, Han Seung Min, a renowned and high-profile professor of forensic psychology – and Yoo Hee’s former lover – comes forward to confess to the crime. The police take him into custody and he is eventually sent to a maximum-security prison teeming with some of the nation’s most dangerous inmates. But as Yoo Hee begins to investigate the crime, she cannot shake the feeling that Han Seung Min is not the killer after all, and that he may have other hidden motives for confessing to the crime. But time is running out for her to solve the case: violence reigns in the prison, where Han Seung Min appears to be engaged in a mysterious quest. Will she manage to solve the mystery before time runs out? And if Han Seung Min really didn’t kill her father… then who did?