Gale is a kind, clever yet hotheaded detective living in 1986. He investigates a series of killings targeting young women marked with strange dots on their ankles. He stumbles upon the suspected killer inside a tunnel where one of the victims was found, but loses consciousness after the culprit attacks him. Gale wakes up in the same spot but when he walks out, his world looks different: he has time-traveled 30 years to 2016. He attempts to go back by running inside the mysterious tunnel but fails. To figure out what has happened to him, Gale inevitably assumes the identity of a police officer who shares the same name. Along the way, he learns of a homicide case that resembles the serial killings he was unable to solve in the past. Gale teams up with Alex, a prickly detective, and Jane, an icy criminal psychologist, to solve the murder case that might help Gale return to his time.