Tunnel

In the town of Hwayang, series of murders that took young women's lives away is making everyone feel anxious. Serious Crimes Unit of Hwayang Police Station works day and night to catch the culprit behind the incidents, but for months, they make no progress. At last, Kwang Ho makes a breakthrough and tracks down the murderer behind the murders.

Detective Park Kwang Ho is shocked to find himself transported 30 years forward in time to December 2016, where he assumes the identity of another police officer bearing his name and starts working on a case with a new partner.

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.

Team Leader Sung Shik figures out who Park Kwang Ho's real identity, and Kwang Ho asks him for help finding Yeon Sook. A burglary case leads to murder, and a criminal psychologist, Professor Shin, is brought in for an unusual request.

Park Kwang Ho and Kim Seon Jae investigate a murder in a roadside rest area that brings up memories for Professor Shin Seon Jae. Park Kwang Ho learns that the officer whose identity he assumed is missing.

A stolen identity case causes Team Leader Sung Shik to worry that Park Kwang Ho will be found out. Professor Shin looks into the Jung Ho Young case. Kwang Ho tries again, and in vain, to go back to his time.