Season 1

A young university student Baek Ji-eun gets kidnapped and killed. The investigating detective is Sung-jun and the judge of this case also happens to be his brother, Sung-hoon. Although Sung-jun finds a suspect, the court is not sure whether he is the real culprit or not. As the trial proceeds with a jury, the case draws a lot of attention.

The jury reaches a verdict that Man-chun is guilty and is sentenced to a lifetime in prison. Just when everyone believes that it is now over, Man-chun manages to escape from his convoy and searches for the jurors to seek revenge. However, his vengeance fails and the truth behind the Joker Murder reveals itself.

Sung-jun wakes up after getting hurt from the hostage situation. But the only things that greet him are his parents’ nagging and the news of another woman’s death. While the public believes the second murder is done by a copycat killer, Sung-hoon gets a hunch that Man-chun is innocent and that there truly is someone else behind the Joker cases.

The jurors are being targeted as the Joker murderer’s victims. As Ki-nam and Moon-kang learn that the cases are related to Hope Welfare, they collect evidence to find their daughters’ killer. Eventually, their investigation leads to the idea that Ryu Sung-jun might be Jung Yoon-jae. Believing this as a fact, Moon-kang kidnaps Sung-jun.

Sung Jun manages to escape from Moon Kang thanks to Eun Ki. As she believes that Sung Jun is not the killer of the Joker Murders, she helps him clear his name. However, the public and the police are certain that he is the culprit. Being chased by his own colleagues, he must prove that he did not kill anyone.

Sung Hoon believes that Sung Jun is not the culprit. Not because they are brothers, but because the current evidence is not enough, and that new evidence starts emerging. Kwon Yu Na gets attacked by Choi Soon Gil. As he is one of the suspects in Yeom Hye Jin’s murder, Sung Jun begins digging into him deeper.

The jurors gather at Kang Young Ki's daughter's wedding while new clues put them into disarray. With everyone gathered, another incident ensues and makes everyone anxious. Was everything planned in detail to get the jurors together from the start?

The murder at the wedding has everyone scrambling. An Tae Ho gets spotted on surveillance footage, and the police put an APB on him. Meanwhile, Sung Jun chases after An Tae Ho but loses him. Later, a strange text message gets sent to everyone, making the situation dire.

Sung Jun and Sung Hoon are too late, and the "Save Me" event ends in tragedy. However, it's still not over. They get confronted by Moon Kang and his men and almost lose their lives. Luckily, the police arrive just in time, but Sung Jun get taken into custody.

Sung Jun finds out Eun Ki's mother had worked as a nurse at Hope Welfare Center. To further investigate, Sung Jun goes to meet her. When he finds her, Eun Ki's mother shakes nervously. That night, Sung Jun senses that Eun Ki could be in danger and races to the children's center to see her. Will something happen to Eun Ki?

Sung Jun tracks down Sung Hoon to save Eun Ki, but his suspicions are wrong. However, Sung Hoon's story doesn't add up, and Sung Jun still feels like Sung Hoon is hiding something. While tailing his brother, the man in black suddenly appears before him.

Sung Hoon recovers in the hospital after getting stabbed by the culprit. Sung Jun confronts Chief Yeom about Hope Welfare Center and gets told to find out from his mother, Minister Na Guk Hee. Meanwhile, Eun Ki sees Yu Na's dying message and hopes it isn't the person she thinks it is. Later Sung Jun finds evidence that it's the same person at a different location.

Eight people, including Eun Ki, suddenly disappear. Could the culprit they've been after all this time be responsible for gathering the eight people in one location? Or could it be a different culprit? Will Sung Jun be able to save the eight people's lives?

The eight people held captive and on the brink of death make it out alive. Sung Jun arrests Jung In Seong and takes him into custody. However, he needs more evidence to connect him to the other serial murders. He looks to Sung Hoon for help and manages to get a lead. Meanwhile, Eun Ki proposes exposing the truth about Hope Welfare Center to Sung Hoon.

Sung Jun regains his memory. His suspicions against his brother were true. He questions Jung In Seong for more answers to guess Sung Hoon's next move. Meanwhile, shortly after Sung Jun learns through a court sentencing that the presiding judge of the Hope Welfare Center case twenty years ago was his father, Ryu Il Ho, he rushes to find him.

It turns out Sung Hoon and Sung Jun’s parents are taking a big part in the secret behind Hope Welfare Center. Despite the sorrow, Sung Jun must arrest both of his own parents. After their arrest, Sung Hoon also gets arrested for the murders. Regardless of the judgment that he will get, he is relieved to fulfill his lifelong revenge.