- Subtitles: English
In 1986, Park Gwang-ho works as a successful detective in an enthusiastic manner. However, his life changes when he takes the lead in a serial homicide case and when he passes through a tunnel while chasing the "culprit". He time travels 30 years into the future (2016), where he meets a new partner, Kim Seon-jae, an eccentric elite detective that has a high ability in investigation. When the serial killer continues his "modis operandi" of his murders that happened 30 years ago, the detective duo works together with a Criminal psychologist, Professor Shin Jae-yi to solve the unsolved murders and to catch the murderer.