TV series

Signal

Name: Signal
Released: 2016
Cast: Lee Je-hoon, Kim Hye-soo, Cho Jin-woong

2016· 2 seasonsTV-MA★ 8.2Ended

On tvN — From AStory · Studio Dragon

📺 Season 2 premieres Dec 7, 2026 (in 31 days)

There are those who are born monsters, but there are also those who are made into monsters by people.

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Where to watch

Not available to stream in US

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Synopsis

 Detectives from the present and a detective from the past communicate via walkie-talkie to solve a long-time unsolved case.

Themes

corruption investigation murder tragic past signal changing the past or future butterfly effect dark suspense thriller awestruck

Episodes

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E1 You're DoomedNext upJan 22, 2016 · 67 min · ★ 8.4
Synopsis
Profiler Park Hae-young hears a man calling his name through a discarded two-way radio. The voice starts talking about an unsolved crime.
Guest stars: Jang Hyuk-jin (Celebrity News Journalist), Oh Yeon-ah (Yoon Soo-ah), Song You-hyun (Kang Se-young), Seo Jung-joon (Seo Hyung-joon), Jeong Jong-yeol (Police Sergeant), Choi Hyun-joon (Detective), Lee Yeong-eun (Kim Yoon-jung), Kim Soo-jin (Kim Yoon-jung's Mother)
E2 We Still Have a ChanceJan 23, 2016 · 66 min · ★ 8.2
Synopsis
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.
Guest stars: Oh Yeon-ah (Yoon Soo-ah), Song You-hyun (Kang Se-young), Seo Jung-joon (Seo Hyung-joon), Sung Hyun-mi (Jung Kyung-soon), Kim Ki-cheon (Lee Chan-goo), Lee Ki-seop (Lee Jin-hyung), Lee Shi-a (Kim Won-kyeong), Choi Hyun-joon (Detective)
E3 We Can Prevent the KillingsJan 29, 2016 · 65 min · ★ 8.0
Synopsis
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.
Guest stars: Sung Hyun-mi (Jung Kyung-soon), Kim Ki-cheon (Lee Chan-goo), Lee Ki-seop (Lee Jin-hyung), Lee Shi-a (Kim Won-kyeong), Lee Do-yeop (Detective Park), Hong Seok-bin (Lee Mi-sun's Husband), Nam Sang-ran (Hwang Min-joo), Kim Jung-young (Kim Won-kyeong's Aunt)
E4 We Found the KillerJan 30, 2016 · 65 min · ★ 8.0
Synopsis
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.
Guest stars: Sung Hyun-mi (Jung Kyung-soon), Kim Ki-cheon (Lee Chan-goo), Lee Ki-seop (Lee Jin-hyung), Lee Shi-a (Kim Won-kyeong), Lee Do-yeop (Detective Park), Hong Seok-bin (Lee Mi-sun's Husband), Oh Jin-ha (Sehoon Hospital Nurse), Nam Sang-ran (Hwang Min-joo)
E5 Changing the Past Alters the PresentFeb 5, 2016 · 68 min · ★ 7.5
Synopsis
Hae-young starts to investigate Jae-han's disappearance. Jae-han's former colleagues get suspicious about seeing Hae-young digging into the past.
Guest stars: Choi Woo-ri (Shin Yeo-jin), Kim Myeong-joong (Prison Guard), Jeong Seok-yong (Oh Gyung-tae), Park Si-eun (Oh Eun-ji), Yoo Ha-bok (Shin Dong-hoon), Kang Joo-hee (Shin Dong-hoon's Wife), Seo Ju-hee (Cha Soo-hyun's Mother)
E6 Catch Him by All MeansFeb 6, 2016 · 70 min · ★ 8.0
Synopsis
Seeking vengeance for the events that lead to the death of his daughter, Kyung-tae commits a kidnapping after getting out of prison for burglary.
Guest stars: Choi Woo-ri (Shin Yeo-jin), Kim Myeong-joong (Prison Guard), Jeong Seok-yong (Oh Gyung-tae), Park Si-eun (Oh Eun-ji), Yoo Ha-bok (Shin Dong-hoon), Sun Yul-woo (Detective), Im Cheol-soo (Informant), Lee Dong-ha (Han Se-gyu)
E7 We Must Dig DeeperFeb 12, 2016 · 67 min · ★ 7.8
Synopsis
Jae-han arrests Se-kyu for the serial burglary case, but the culprit is freed after serving a short sentence; Kyung-tae still commits murder.
Guest stars: Choi Woo-ri (Shin Yeo-jin), Son Hyun-joo (Jang Young-cheol), Jeong Seok-yong (Oh Gyung-tae), Park Si-eun (Oh Eun-ji), Yoo Ha-bok (Shin Dong-hoon), Im Cheol-soo (Informant), Lee Dong-ha (Han Se-gyu), Yoon Bok-sung (Attorney)
E8 How Are You Alive?Feb 13, 2016 · 74 min · ★ 8.6
Synopsis
Soo-hyun and Hae-young notice a connection between the burglary case and Da-hye, the woman who killed herself twenty years ago.
Guest stars: Lee Dong-ha (Han Se-gyu), Lee Na-ra (Shin Da-hye), Kim Ryeo-eun (Kim Ji-hee), Yoo Jae-ik (Oh Seung-joon), Yang Eun-yong (Sin Jeong-hye), Hyun Sung (Min Sung)
E9 Hongwon-dong CaseFeb 19, 2016 · 74 min · ★ 8.4
Synopsis
Hae-young learns that Chi-soo and Jae-han met in 1999 during a case in Inju. After serving time for the crime, Hae-young's brother had killed himself.
Guest stars: Im Cheol-soo (Informant), Park Seong-hoon (Detective Jung), Im Yong-soon (Workshop Owner), Lee Sang-yeob (Kim Jin-woo), Seo Eun-ah (Yoo Seung-yeon), Yang Seung-geol (Street Cleaner)
E10 Someone Has to Stop the Bad GuysFeb 20, 2016 · 72 min · ★ 7.8
Synopsis
The bodies discovered in the mountains appear to be more victims of the 1997 serial murder case. Jae-han learns that Soo-hyun became team leader.
Guest stars: Lee Sang-yeob (Kim Jin-woo), Seo Eun-ah (Yoo Seung-yeon), Lee Chae-kyung (Jin-woo's Mother), Song Kyung-hwa (Convenience Store Owner)
E11 The One Last CaseFeb 26, 2016 · 78 min · ★ 7.8
Synopsis
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.
Guest stars: Son Hyun-joo (Jang Young-cheol), Ji Hye-in (Girl 3), Lee Sang-yeob (Kim Jin-woo), Seo Eun-ah (Yoo Seung-yeon), Park Eun-young (Student's Mother), Kim Hak-sun (Park Myung-hoon), Hong Boo-hyang (Farmer's Wife), Jeon Su-ji (Kang Hye-seung)
E12 The Case Was ManipulatedFeb 27, 2016 · 78 min · ★ 8.2
Synopsis
Hae-young becomes a suspect for the murder of Chi-soo. Jae-han realizes who the principle offender of the attack on Hye-seung is.
Guest stars: Kim Hak-sun (Park Myung-hoon), Hong Boo-hyang (Farmer's Wife), Jeon Su-ji (Kang Hye-seung), Shin Yi-Joon (Kang Hye-seung (Young)), Seo Ji-hoon (Jang Tae-jin), Kim Woo-seok (Lee Dong-jin), Lee Jin-kwon (Bully), Sung Ki-yoon (Hae-yeong's Father)
E13 The Real AssailantMar 4, 2016 · 74 min · ★ 8.0
Synopsis
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.
Guest stars: Jeon Su-ji (Kang Hye-seung), Shin Yi-Joon (Kang Hye-seung (Young)), Seo Ji-hoon (Jang Tae-jin), Kim Woo-seok (Lee Dong-jin), Lee Jin-kwon (Bully), Hwang Seung-eon (Han Do-yeon), Lee Jae-eun (Market Stall Owner), Kang Chan-yang (Woman Going to Work)
E14 Not Now, but Maybe in the PastMar 5, 2016 · 74 min · ★ 8.0
Synopsis
Hae-young realizes the possibility that his brother could have been murdered after learning from Hye-seung that Sun-woo was not guilty.
Guest stars: Son Hyun-joo (Jang Young-cheol), Jeon Su-ji (Kang Hye-seung), Shin Yi-Joon (Kang Hye-seung (Young)), Seo Ji-hoon (Jang Tae-jin), Kim Woo-seok (Lee Dong-jin), Shin Mun-sung (Detective), Sung Ki-yoon (Hae-yeong's Father)
E15 Is It Really You?Mar 11, 2016 · 72 min · ★ 8.0
Synopsis
Hae-young is arrested for the murder of Chi-soo. Soo-hyun hears Jae-han apologizing over the radio for not being able to prevent Sun-woo's death.
Guest stars: Son Hyun-joo (Jang Young-cheol), Jeon Su-ji (Kang Hye-seung), Shin Yi-Joon (Kang Hye-seung (Young)), Seo Ji-hoon (Jang Tae-jin), Kim Woo-seok (Lee Dong-jin), Oh Ki-hwan (Detective)
E16 If You Don't Give UpMar 12, 2016 · 89 min · ★ 8.4
Synopsis
Hae-young is in critical condition after being shot while meeting with Sung-bum. In 2000, Jae-han has been captured by Bum-joo.
Guest stars: Son Hyun-joo (Jang Young-cheol), Jeong Jong-yeol (Police Sergeant), Jeon Su-ji (Kang Hye-seung), Shin Yi-Joon (Kang Hye-seung (Young)), Seo Ji-hoon (Jang Tae-jin), Kim Woo-seok (Lee Dong-jin), Sung Ki-yoon (Hae-yeong's Father)