S1 • E1
The main protagonist tries to help the police catch a killer that kidnapped and murdered his childhood schoolmate 15 years ago.
S1 • E2
Park Hae-young continues to try catching the culprit that kidnapped his childhood schoolmate and after that they began a small police force which solved outdated unsolved cases and they are starting on a popular serial killer case.
S1 • E3
The search for the serial killer continues as the main protagonist tries to change the case by communicating with a detective from the past.
S1 • E4
The cold case squad figures out who the serial killer is, but not before the wrong suspect turns himself in.
S1 • E5
Park Hae Young begins asking questions about Lee Jae Han. Meanwhile, the police force in Lee Jan Han's time struggles with a string of larceny cases.
S1 • E6
Park Hae Young figures out that Oh Kyung Tae's true objective is the father of the girl he kidnaps.
S1 • E7
Lee Jae Han catches the real culprit behind the burglaries, unwittingly changing the past for the worse again.
S1 • E8
The cold case squad finds Shin Da Hye, who has been living under the murder victim's identity.
S1 • E9
Park Hae Young uncovers another layer to Lee Jae Han's disappearance. An old demon from Cha Soo Hyun's past resurfaces.
S1 • E10
The Cold Case Squad is assigned to the serial murder, but the last the victims isn't identified. Cha Soo Hyun revisits a past trauma.
S1 • E11
The Cold Case Squad catches the Hongwon-dong serial killer, but Lee Jae Han's determination changes the past again.
S1 • E12
Park Hae Young becomes the prime suspect for the Section Chief's murder. Meanwhile, Lee Jae Han must find out who this "one" is before it's too late.
S1 • E13
Park Hae Yeong and Cha Soo Hyun are waiting for the DNA results of the corpse they found. Meanwhile, they remember Lee Jae Han. Hae Young discovers that he was never alone, and Soo Hyun remembers the last time she saw her sunbae and her 15-year waiting for their reunion.
S1 • E14
Following the trail the Section Chief left, Park Hae Young uncovers the truth behind his brother's death. Meanwhile, Cha Soo Hyun finds Lee Jae Han's radio in Hae Young's possession.
S1 • E15
Park Hae Young is framed and arrested for the murder of the Section Chief. Cha Soo Hyun sets out to save Lee Jae Han and to find the one witness who can bring down their enemy.
S1 • E16
Lee Jae Han is set on bringing down Kim Bum Joo, despite knowing that he's going to die, but a certain transmission is about to make all the difference.
Park Hae-yeong
Cha Soo-hyeon
Lee Jae-han
Kim Gye-cheol
Kim Hae-chul
Cha Soo-Min
Kim Jin-Woo
Lee Chun-goo
Yeo Jin's father