Number of Episodes: 16

Released Year: 2016

Main Plot:

Signal is a Korean crime-thriller drama inspired by real-life unsolved cases. The story follows detectives from different timelines who communicate through a mysterious walkie-talkie. By connecting the past and present, they attempt to prevent crimes and catch culprits who had escaped justice for years. With suspense, emotions, and moral dilemmas, Signal delivers a powerful narrative about justice and fate.

Main cast:

• Lee Je-hoon as Park Hae-young (Profiler, present timeline)
• Kim Hye-soo as Cha Soo-hyun (Detective, present timeline)
• Cho Jin-woong as Lee Jae-han (Detective, past timeline)

Episodes Summary

Episode 1: The Mysterious Walkie-Talkie

One day in 2000, Park Hae-young, a little child, waited outside the Seoul elementary school for his classmate Kim Yoon-jung after class.Yoon-Jung was never seen outside after class. Later, Yoon-jung and an unidentified woman leave the elementary school, and Hae-young bolted to the police station because he feared he was going to die after witnessing the woman shove Yoon-jung out of the school. The officers dismissed him because they had arrested a suspect.

The actual kidnapper eludes detection, but Yoon-jung’s body is discovered a few days later. This terrible event causes Hae-young to lose faith in law enforcement and think that the police are not trustworthy when it comes to safeguarding the weak.

Hae-young was elevated to lieutenant and profiler in the police force in 2015, fifteen years after the incident. His encounter with Yoon-jung’s former schoolmate while investigating a case of celebrity abuse brings back painful memories of her unsolved murder. On the same night, a walkie-talkie that had been stored in the police junkyard and left there springs to life. At the other end there is a man’s voice, essential, strong and foreigner. With a live hearing air, the man presents himself as Lee Jae-Han and begins to interrogate him about her kidnapping.

Startled but intrigued, Hae-young initiates a second investigation into the crime right away. He considers the odd woman he had seen with Yoon-jung in 2000 while following this course. His discovery of the old CCTV footage suggests that the woman was present with the victim, confirming that the wrong man was arrested. Due to the persistence of Hae-Young, the case is reopened and the falsely accused defendant, who had been imprisoned for years, eventually is excluded.

Cha Soo-hyun, a devoted detective who served under Jae-Han and spent years attempting to resolve his esoter disappearance, is interested in a fresh case. She initially finds the direct and disobedient conduct of Hae-young disappointing, but she eventually comes to appreciate his deep profiling abilities and penance.

The walkie-talkie is restarted at the same time. The exact fact is that JaeHan’s voice was telling at that time, only one could be known by those who were part of the first investigation. Ultimately, Hae-Young learns that the voice is actually of a detective Jae-han from the year 2000 instead of the present. Despite his dissatisfaction with the unavailable link, he is determined to pay attention.

The reason for Yoon-jung’s death is ultimately revealed at the end of Episode 1: she was abducted by the lady Hae-young had seen years before, but the original investigation disregarded her. Hae-young is very troubled by the unfairness of the wrongfully convicted guy receiving a fifteen-year sentence. But at the same time, he starts to worry that the strange link to Jae-Han could reveal the outcome of other cases.  As the show ends, the walkie-talkie returns to life and the voice of Jae-Han breaks peace, serving as a chilling reminder, the past and present are unwavering.

Episode 2: Clues Across Time

It is almost time to wrap up the 2015 kidnapping case of Yoon Jung. Yoon Soo Ah, the suspect, is being pressured by the police to confess because the statute of limitations is about to expire. There is an obvious sense of stress since they know that this is their only chance. Soo Ah is approached by Detective Cha Soo-hyun, the lead investigator, who subtly suggests that the DNA found on a second victim’s glasses could establish her guilt. Soo Ah remains calm despite being under a lot of stress and refuses to recognize anything.

In an attempt to secure a breakthrough, Park Hae-young takes a chance by creating DNA evidence to persuade her that the police can prove her involvement. The scheme fails despite his meticulous preparation. As the clock strikes the end, Soo Ah remains steadfast, officially ending the statute of limitations. Disappointed and helpless, the team looks on in frustration as the culprit escapes.

Hae-young is sent to a newly created cold case investigation section, which is headed by Detective Soo-hyun, following this failure. They started with horrific Hwaseong serial killings, which took place decades ago and are still unresolved. To find out what the first investigation ignored, the team gathers to go through old reports, images and assistant documentation.

Hae-young is going through the cold case files that night when the abandoned walkie-talkie comes to life. The voice of Detective Lee Jae-Han has been immediate and familiar since 2000. A missing woman who may be the next victim of the Hwaseong Killer is focused on frustration.

As Jae-han describes the pitch-black fields and roads, Hae-young listens in shock, calling her name and frantically attempting to get to her in time. The radio waves appear to bring the past and present together, creating an instant tension.

Jae-han does his hardest, but he can’t save the woman. Another victim was added to the list of serial killers in 2000 when her body was found the next morning. Hae-young is seated in 2015, speechless and in shock at what he has witnessed.

A melancholy note ends the show. The regretful and melancholy tone of Jae-han’s voice wanes over the walkie-talkie.  The sound of Jae- han’s voice and sadness is on the tone walkie-talkie. Their pain on their failure to protect the woman through time. As Hae-Young hears in 2015 in a calm form, he is shaken by the weight of these unresolved cases and odd, inexplicable connections that bind it to their past. Although the investigation of cold cases has begun, the reality of failure and loss still allows work, creating a stressful and emotional environment.

Episode 3 : A Path through Time

The episode starts with another devastating loss. The two detectives; Lee Jae-han from 2000 and Park Hae-young from 2015 have both failed to prevent the missing woman from being killed by the Hwaseong serial killer in their own way. Despite fifteen years passing, their sense of pain, frustration, guilt and their drive to protect any more innocents from being killed stays the same. They must find a way to prevent such a thing from happening.

The investigation continues in 2015 with Hae-young looking over all of the evidence collected against the case such as reports, pictures and evidence from witnesses and finds new details in the investigation which were overlooked before. He continues to find evidence proving the police investigation in the Hwaseong murders was a mishandling case.

The investigation also takes a turn in 2000 with Jae-han who believes he is able to gather his own evidence against the case, he is not persuaded that the evidence has already been gathered and takes new leads that are being looked over. The more he gets on the case and gets close to the true killer, the more he is in conflict with other police investigators and even his own team.

 Later that evening the strange walkie talkie re-connects with both detectives. Following both messages, they have decided they must stick with their connection in order to finally solve the case. By communicating with each other over time, they start to gather bits of information together which none of them would have ever thought to get before.

As the investigation becomes more and more intense, shocking new evidence is presented and begins to challenge everything they believe to be true. The evidence gives them a new lead in the investigation with a major breakthrough, the episode is extremely intense in anticipation to see where this breakthrough leads to and for what is to come for the detectives with their operation as the cases get much more dangerous and complex.

Episode 4 : The Killer’s Secret Unveiled

In Episode 4 we see an extreme turn in the investigation as Park Hae-young and Lee Jae-han get closer to the truth surrounding the Hwaseong serial murders. The detectives believe there is something still amiss, though the police think they have finally got their man, Hae-young has a gut feeling the investigation is not over and more is to come.

In 2000, Lee Jae-han was deeply distressed after Kim Won-kyung’s appalling murder. Still unable to forgive himself for failing to protect her he is more determined to capture her murderer and still attempts to find proof other than the official story, which doesn’t appease him though his superiors would be inclined to believe he is wasting his time.

Meanwhile the Cold Case Team discovers Bus 95 and its driver Lee Chun-goo is directly linked to the killings in 2015, he eventually confesses his sins, although his quick confession leaves the police with few questions the team cannot quite accept that it is over and there must be something that isn’t right, they don’t believe that Chun-goo could be the killer alone.

When investigating Chun-goo’s son, Detective Cha Soo-hyun finds new evidence leading her into a dangerous situation with some worrying connections to the case. The truth slowly begins to unravel.

When Park Hae-young discovers evidence which directly links Chun-goo to protecting his son from the charges it becomes clear the real killer of the Hwaseong serial murders was Lee Jin-hyung who evaded the police for many years as he got his father arrested instead. The episode concludes sadly but positively with all the victims and families getting the justice they deserve, leaving Jae-han troubled with all those who have been killed.

Episode 5 : Altering the past changes the future

The episode starts as the Cold Case Team is praised for finding out who was behind one of Korea’s most notorious crimes, Park Hae-young can no longer bring himself to celebrate and remains fixated on Detective Lee Jae-han’s disappearance. His investigation soon leads to his own set of troubling questions about the case.

Hae-young discovers an alarming document within previous police records which states that Lee Jae-han had already officially been declared missing for years. What is also disturbing is the documents suggest that he was somehow involved with police corruption, Hae-young refuses to believe it was true and decides to take a look into his background.

The storyline then travels back to 1995 where a younger Cha Soo-hyun meets Lee Jae-han for the first time since she has joined the police department, a very awkward but memorable first meeting. At the same time Lee Jae-han finds himself entangled in a number of bizarre robbery cases, with no leads left to follow, he is desperate to solve the cases.

Later in 2015 when Park Hae-young is still researching further, a new kidnap case involving a wealthy professor occurs, and once there are a number of links connecting a former thief known as Oh Kyung-tae to the case, he is quickly arrested as a suspect, however Park Hae-young finds certain discrepancies in the evidence and believe that the truth behind the case is more complex than it first appears.

Their walkie-talkie then makes another appearance, and after revealing the vital information from each time, it is clear that the changing of events in the past may be creating unforeseen problems for the future, the episode ends with a chilling end with Lee Jae-han realizing how serious everything has gotten.

Episode 6 – The Past Fights Back

Episode 6 is kicked off as Park Hae-young and Lee Jae-han scramble to find out what is happening with the kidnap case and discover more to what was originally perceived. Oh Kyung-tae is still being portrayed as a criminal but both detectives begin to realize that this isn’t necessarily the truth as more facts about the crime and the victim come to light.

They soon uncover the traumatic experience which has changed Kyung-tae’s life forever, the death of his young daughter during the fatal collapse of the Seongsu Bridge and he could no longer accept that nothing was being done and he felt he had been left to suffer. This pain is what eventually led him down the path to committing the crimes.

Meanwhile Jae-han learns that there are claims that Kyung-tae may not have been guilty in a previous robbery case, he uncovers that a number of key pieces of evidence have been manipulated and this is why he could not forgive what he thought had happened, this leads him to realize there are clearly people who are desperate to get what they are doing hidden.

Back in 2015, they rush to save the kidnapped girl before it is too late, but before they can get to her the police team and the girl’s life are completely shattered by a devastating explosion, Park Hae-young realizes that this is another consequence to the alterations made in the past.

The two detectives begin to piece together the events and slowly uncover a much larger conspiracy, the case has now become significantly more dangerous. By the end of the episode they begin to unravel what has happened but find there are still many secrets to uncover regarding who is behind all of these events and why.

Check this another thriller Korean drama with full of suspense.