A dismembered body abandoned in a rural irrigation ditch in the middle of the night! A peppermint candy is found inside the corpse's mouth, and the detectives at the scene are reminded of 'The Guy,' a serial killer who died five years ago. Hwang Ha-young, the team leader of the Major Crimes Unit Team 1, discovers Soo-young, a police officer from a local precinct who remembers every detail of the crime scene exactly as she saw it, and sends her to a mysterious man...

Major Crimes Team 1 discovers that a victim has been kidnapped by the suspect who surrendered. As the possibility of the victim's survival emerges, Team 1 locates the suspect's hideout. Soo-young enters the basement of a crumbling building in search of the victim, but after losing radio contact with Team 1, she finds herself in danger...

Who murdered the suspect who surrendered? Oh Hyun-jae and Cha Soo-young discover that the murdered suspect has an accomplice and find clues about the accomplice at the suspect's house. Meanwhile, the accomplice begins searching for a new victim. Will Team 1 be able to save the them?

A mysterious message is delivered to Team 1. Peppermint candy is found at the scene once again! Oh Hyun-jae analyzes the message to identify 'The Guy's' next target, while Team Leader Hwang Ha-young rushes to stop the predicted murder alongside Cha Soo-young. Mysterious Message X Predicted Murder! If you want to stop it, tell them what you saw!

Oh Hyun-jae and Cha Soo-young fail to prevent the predicted murder! With the murder occurring during a live broadcast, the media focuses on the return of "Peppermint Candy," while Soo-young discovers traces of a mysterious man breaking into her goshitel. Meanwhile, Hyun-jae warns Soo-young to be careful, saying "The Guy" is watching, and Soo-young remembers that the mysterious man is the same one she encountered at the police station...

"The Guy" locates Oh Hyun-jae's hideout through Cha Soo-young! However, Hyun-jae does not show himself, and "The Guy" discovers unexpected traces at the hideout. Meanwhile, Team Leader Hwang and Soo-young head to the hideout to rescue Hyun-jae, and Hyun-jae senses the hand of death approaching...

Oh Hyun-jae stands up from his wheelchair and begins to move! Meanwhile, Soo-young learns that the child she met has been kidnapped and requests Hyun-jae's cooperation once again. The suspect's vehicle is found abandoned on a mountainside. However, no decisive clues to find the missing child are discovered, and Oh Hyun-jae uses Soo-young's "picturing" to identify a factory where the child is presumed to be, but soon discovers traces of burial at the scene...

Team 1 heads to a closed amusement park to rescue a child. They search for traces of the kidnapped child in a fun house, but all they find is evidence that there was another child besides the abducted one! Meanwhile, the child hides in the Mirror Room to escape the woman chasing him, and Oh Hyun-jae and Cha Soo-young are shocked to see someone who shouldn't be there while following the child's trail...

Ha Tae-sik, arrested as a suspect in a new murder case, mentions another secret related to the bombing incident five years ago, and Oh Hyun-jae tries to uncover the hidden secret in less than 48 hours. Meanwhile, Soo-young finds a clue regarding the hit-and-run vehicle that killed her mother, and Hyun-jae discovers something strange in the witness statement regarding the Ha Tae-sik case.

Hyun-jae finds a clue from Ha Tae-sik that leads him closer to "The Guy". While chasing the lead, Hyun-jae learns of the existence of a psychiatric ward, and Soo-young discovers an unexpected commonality among the serial murder cases. Meanwhile, a hanged body is found in a mountainous area of ​​Soo-young's hometown, Hwayoung-gun, and Team Leader Hwang Ha-young proposes sharing information with an unexpected individual...

A series of mysterious suicides occur. While investigating the suicides, Soo-young confronts the truth behind the hit-and-run accident that killed her mother. Meanwhile, Oh Hyun-jae, Team Leader Hwang, and Chief Choi each begin chasing "the culprit", following the clue of the number 4789 left by Ha Tae-sik...

As the shocking past that has suffocated Hwang Ha-young for five years is revealed, and amidst the tragedies uncovered as the past unfolds, "The Guy" begins to gradually make his presence known... "You have already seen everything!"

The list of suspects is getting shorter. Team Leader Hwang begins to narrow in on "The Guy". Realizing the investigation is tightening around him, "The Guy" contemplates his next move... Meanwhile, Soo-young notices the dangerous plan!

Hyun-jae confronts "The Guy". What will his reaction be? Team Leader Hwang's unexpected and impulsive actions make the case increasingly unpredictable, and secrets hidden beneath the surface are brought to light...

Team 1 is thrown into chaos as they discover the true identity of "The Guy". Meanwhile, "The Guy" meets an unexpected person to turn the situation around. Hyun-jae, Soo-young, and Team Leader Hwang all rush to catch him.

Hyun-jae, "The Guy", and Team Leader Hwang face their final showdown! The catastrophe that began five years ago is approaching for the three, and Soo-young struggles to stop the recurring tragedy...