Kim Seon Jae, believing Kwang Ho to be an identity thief and murderer, offers to help him investigate the other Kwang Ho, who died under mysterious circumstances. Meanwhile, the investigation into the serial killer's whereabouts continues.
Kim Seon Jae struggles to hold onto his composure as the police once again try to force Mok Jin Woo to confess. When all is over and after saying goodbye to his adult daughter, Kwong Ho goes back to 1986. All loose ties are connected.
The police turn their attention to the second murderer. Kwang Ho begins to suspect Professor Mok, who has figured out who Kwang Ho really is. Pr. Mok lures Kwang Ho into a confrontation.
While the police scramble to pin down Jung Ho Young's location, Pr. Shin, being the only one who believes that he isn't responsible for all of the murders, decides to take action. Kwang Ho discovers who Pr. Shin is.
Park Kwang Ho and Kim Seon Jae,, who found a new respect towards each other, agree to investigate the Jung Ho Young case together. The police team tracks down an arsonist.
While searching for more evidence to convict Jung Ho Young, the police realize that they dealing with more than one killer. Kwang Ho cannot bring himself to tell Pr. Shin who he really is.
After jumping back to 1986 and reuniting with Yeon Sook, Kwang Ho tries to locate the second killer before he kills victim #5. Meanwhile, in 2017, the team's and Pr. Shin's search for Kwang Ho reveal that he was on a lead.
With Jung Ho Young attracting the public's attention and becoming bolder, the entire police station is ordered onto his case. Park Kwang Ho discovers what happened to his wife after he disappeared 30 years ago.
While Park Kwang Ho and Kim Seon Jae are searching frantically for Pr. Shin, she stalls for time after being kidnapped by Mok Jin Woo, hoping that the police will be able to track him before he kills her.
Detective Park Kwang Ho, after realizing that he's unable to go back to 1986, is convinced he was sent to the future to solve the 30-year-old serial murder case, but clashes with his coworkers over a new unidentified victim.