信號

海英在某處撿到一支舊對講機，並從中得知了綁架懸案的線索。

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.

海英加入懸案專案小組，而材韓也透過對講機透露了一些事。

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.

發覺對講機上的對話竟然改變了過去後，海英感到困惑不已。

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.

儘管上司反對，專案小組仍著手調查京畿道南部案件。

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

海英一步步接近材韓失蹤的真相。

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.

海英持續努力扭轉糾纏不清的過去和未來。

秀賢死後，海英仔細思索自己是否該繼續留著對講機。

Soo-hyun and Hae-young notice a connection between the burglary case and Da-hye, the woman who killed herself twenty years ago.

查看了多惠的指紋後，專案小組隨即開始追蹤她的下落。

海英懷疑治秀可能涉及材韓的失蹤。

材韓透過對講機，得知秀賢和海英如今隸屬同一個專案小組。

Hae-young and Soo-hyun arrest Jin-woo after coming to the conclusion that he is the killer. Hae-young asks Jae-han about the Inju rape case.

材韓前往仁州調查仁州女高中生性暴力事件。

Hae-young becomes a suspect for the murder of Chi-soo. Jae-han realizes who the principal offender of the attack on Hye-seung is.

秀賢得知材韓遭治秀殺害後震驚不已。

Soo-hyun and the others mourn after confirming that the remains belong to Jae-han. Hae-young learns that Jae-han used to look after him in the past.

材韓前往仁州，並發現海英原來是善宇的弟弟。

海英前往仁州審問當年指認親哥哥為主謀的人。

隨著善宇的死期逼近，材韓匆匆趕往仁州拯救海英的哥哥。