This drama tells how difficult it is to realize justice. What if a child has been kidnapped, but the culprit is right in front of you? Will you save the child no matter what? Or will you still choose to go through all the procedures not to make a false accusation of the suspect? If the missing child was your family, would you keep saying that we must go through all procedures? If your child was kidnapped, what choice would you make? Less than Evil makes us ponder about various types of justice we should pursue in our society. Detective Woo Tae Seok, the main character, tries his best to catch the bad guys who always evade laws by any means. One day, a psychopath Eun Seon Jae shows up in front of Woo Tae Seok, and that's where the story begins. Will Detective Woo Tae Seok catch the psychopath following all protocols? Or, will he choose the way that might go against the procedures that detectives must comply with?