In 1990, detective Choi Hyeong-goo Jung Jae-young tracks a serial killer who has taken ten victims since 1986 and is suspected of kidnapping another. After a brutal confrontation, Choi is left battered and scarred, the killer eluding capture as Choi fires a final shot that strikes him in the shoulder before the killer slips away.
By 2005, with the clock ticking toward the statute of limitations, Choi—now an alcoholic haunted by his own failure—receives a desperate call from Jung Hyun-sik Ryoo Je-seung, a family member of one of the victims, who then leaps to his death from a passing vehicle. The case lingers in his mind as the years roll on.
Two years later, a man who calls himself Lee Doo-seok Park Si-hoo publishes a sensational memoir titled I Am the Murderer, claiming responsibility for the ten murders. The book, bolstered by Lee’s butterfly-light charm and the grisly details of the crimes, becomes a bestseller. He conducts public visits to the families to beg for forgiveness, even approaching Choi at the precinct, while Choi dismisses him as a fraud.
As media attention swells, the victims’ families rally under Han Ji-soo Kim Young-ae, including the mother of the still-missing 11th victim, Soo-yeon. They hatch a dangerous plan—releasing snakes into Lee’s hotel pool and then staging a fake medical convoy to abduct him, slipping him away to a motel while an unconscious Lee is spirited out of sight. Choi pursues and rescues, but leaves Lee with a warning to stay quiet.
A televised debate about the case pulls Choi and Lee into the spotlight, with a chilling caller named J taunting Lee and revealing intimate details about Choi. The investigation intensifies as Choi discovers a videotape of Soo-yeon tied up and killed, raising the stakes and casting doubt on who the real killer might be.
Choi eventually reveals in a press conference that the truth remains murky, while Lee insists he is innocent and not the author of the book. A second debate erupts, drawing thousands of protesters and fans, with Han ready to strike at the killer with a pen loaded with venom.
Then a dramatic revelation turns the investigation on its head: the killer is not Lee, and Lee did not write the book. In fact, Jung Hyun-sik—who had faked his own death with Choi’s help and undergone plastic surgery to assume a new identity—had collaborated with Choi to lure out the true killer, using the public-facing persona to unmask him.
Despite the shock, J taunts Choi about the expired statute as a videotape appears, showing Soo-yeon’s death on the very date the law would expire. With only minutes left, Choi chases J through a tense pursuit. J escapes, but Choi manages to confront him; a clash ends with Choi stabbing J with the pen to avert a further murder.
In 2012, Choi is released from prison to a chorus of media attention and the relief of the victims’ families. The case results in an extension of the statute to 25 years, reshaping how justice is pursued in this haunting, methodical thriller.
