Despite the show's lacklustre ratings, audiences and critics alike praised its story and the performances of the cast, particularlyPark Bo-gum's performance.[7]
Genius profiler Lee Hyun (Seo In-guk), returns home to Korea after something from a case he has been sent triggers a memory he thought he had lost forever. Unbeknownst to him, one of his team members, Detective Cha Ji-an (Jang Na-ra), has been investigating him for some time. She is aware that his father was murdered and his brother disappeared under mysterious circumstances involving a criminal named Lee Joon Young (Doh Kyung-soo) -- whom they both want found and incarcerated. Each seeks to unravel the other, unaware that they've been drawn into a dangerous game of cat and mouse by a master player and that both truth and evil are closer and far more twisted than they think.
Lee Hyun was a "strange child" who caught the attention of his father, a police inspector, who later confined him in a small room to prevent him from breeding criminal thoughts. An intelligent child, he later studies abroad and becomes a reputed professor. Strangely, he loses his childhood memories, and a series of events lead him to return to South Korea. There he tries to solve numerous murder cases that seem to be linked to one another in order to find his long-lost little brother, whom he presumed to be the serial killer.
Cha Ji-an's father mysteriously disappeared together with Lee Joon-young, a convicted prisoner who was said to have escaped from confinement. She becomes a police inspector and meets Lee Hyun, the boy she has been stalking since her childhood. Their similar circumstances lead them together as they work to solve criminal cases.
Born as a result of rape, Joon-young was neglected as a child. He soon bred murderous thoughts and became a murderer who eventually escaped from prison. 20 years later, he returned with the identity of Lee Joon-ho. His main personality trait throughout the series was depicted as someone who doesn't understand complexities of human emotions while being well versed in their thoughts. For-example, from his perspective, his returning of Cha Ji-an's father's remains was a good deed despite having killed and framed the guy himself. Knowing how her father ended up 20 years ago made her angry at him but he was sad to see Cha Ji-an being angry and couldn't figure out the reason despite it being very obvious to others.
He doesn't think he ever did anything bad since there was always a justifiable reason for himself.
In his own words, Lee Hyun was the kid he wanted to be while Lee Min was the kid who came to resemble him.
Lee Min shared a close relationship with Lee Hyun as a child and often confided his darkest secrets to him. He feels neglected later on as he was under the misconception that he had been abandoned by his brother after their father was murdered. He later appears nearly 20 years later using the name Jung Sun-ho.
Special investigator team member. He is a slightly quiet person. Unbeknownst to the team, he is one of the kids that Lee Joon-young saved from his hellish childhood life.
Malaysia