A mysterious walkie talkie allows a detective in the year 2000 to communicate with a cold case profiler from 2015; with the power of fore and hindsight the two not only solve crimes but prevent them from ever taking place. However, a long-standing murder case is closer to home than either realizes. A detective Lee Jae-han(Cho Jin-woong) tries to create a world where those who have done wrong deserve punishment, but a huge force interferes with it.