Signal

Profiler Park Hae-youn hears a man calling his name through a discarded two-way radio. The voice starts talking about an unsolved crime.

The statute of limitations is lifted after the suspect's arrest. Hae-young joins Soo-hyun's team for the newly established cold case squad.

Reality changes after Hae-young exchanges information with Jae-han. Hae-young tries to work together with Jae-han in 1989 to prevent the next murder.

The ninth victim is Won-kyung, the woman Jae-han loves. A driver turns himself in, but Soo-hyun and Jae-han determine that his son is the real killer.

Hae-young starts to investigate Jae-han's disappearance. Jae-han's former colleagues get suspicious about seeing Hae-young digging into the past.

Seeking vengeance for the events that led to the death of his daughter, Kyung-tae commits a kidnapping after getting out of prison for burglary.