This crime-thriller series asks the question: “what would you do if you could identify psychopaths through a genetic test before they are born”? 

When a vicious serial killer is imprisoned, the story shows us two pregnant women sitting outside a testing center in a hospital. They came in for genetic testing to determine if their unborn child carries the “psychopath gene.” One of the women is married to the serial killer, while the other to a kind and gentle man. Having learned that the babies they carry both have the gene, they must decide what to do about it now.

Decades later, the same killer is still on death row, but a new psychopath is out for blood. Could it be the killer’s son? Is the new killer one of the unborn children that had the psychopath gene?

Jeong Ba-reum (Lee Seung-gi) is a reputable rookie police officer. His life changes after an encounter with a psychopathic killer. This leads him into a mad chase to unearth the truth behind the killer’s psychopathic behaviour with his partner Go Moo-chi (Lee Hee-jun), a man who doesn’t mind bending the rules to catch criminals. 

Go Moo-chi is the way he is because of a childhood trauma. He witnessed the murder of his family by the serial killer now on death row. Now, all he wants is revenge. But along with that burning desire for retribution, he also struggles with a drinking problem and an impulsive behaviour which could threaten his career as a police officer .

Head on, the drama reveals who the new killer is, and this revelation gives viewers a sneak peek of his interesting psychosis and motive for killing. However, this leaves behind a trail of murders causing great fear among the population. 

As the story progresses, it explores the concept that psychopaths are not made, rather they are born to be that way. So that challenges the possibility of conducting genetic testing to determine who are genetically predisposed. And if someone is indeed hardwired from the womb to be an unremorseful criminal, should the parents keep that child?