Signal

Hae-young finds an old walkie-talkie in the corner and gets clues on the unsolved kidnapping case.

Hae-young joins the unfinished case squad and Jae-han says something through the walkie-talkie.

Hae-young is confused after discovering that the talks through the walkie-talkie changed the past.

The squad starts investigating the Gyeonggi Nambu case despite the opposition from their superiors.

Hae-young gets one step closer to the truth of the disappearance of Jae-han.

Hae-young continues to make an effort to change the wrongly intertwined past and future.

After Su-hyeon dies, Hae-young contemplates whether he should keep the walkie-talkie.

After checking the fingerprint of Da-hye, the squad tracks down the whereabouts of her.

Hae-young suspects Chi-soo who might have something to do with the disappearance of Jae-han.

Through a walkie-talkie, Jae-han realizes that Su-hyeon and Hae-young are on the same team.

Jae-han heads to In-ju to investigate the In-ju female student sexual assault case.

Su-hyeon falls in great shock after finding out that Chi-soo killed Jae-han.

Jae-han heads to In-ju and finds out that Hae-young is Seon-woo's younger brother.

Hae-young heads to In-ju and interrogates the person who pointed at his brother as the main culprit.

With Seon-woo's death coming close, Jae-han hurries to In-ju to save Hae-young's brother.

Hae-young does not lose hope of saving Jae-han and immediately grabs the walkie-talkie.