Signal ~ Echoes Across Time That Help Solve Crime

By cmoneyspinner - February 26, 2026

“Signal” is a 2016 Korean drama, 16 episodes, categorized as Time Travel, Crime, Thriller, Police Procedural, Fantasy, Science Fiction (Sci Fi), and Mystery, streaming on Netflix, Tubi TV, The Roku Channel, and Amazon Prime.

Memorable Quote: “We can still save them.”

SUMMARY: A profiler in 2015 communicates with a detective in 1989 through a mysterious walkie-talkie. Together, they solve cold cases and expose corruption. Their collaboration alters timelines, reshaping the lives of everyone connected to the investigations.

♦“If we can change the past, does that mean we can save the future?”

In “Signal”, the story begins with Park Hae-Young, a criminal profiler in 2015 who has long distrusted the police due to a traumatic childhood incident. A classmate was kidnapped and murdered, and the case was mishandled by authorities. His skepticism and mistrust of the institutions shape his career and how he approaches investigations.

One day, Park Hae-Young discovers an old, battered walkie-talkie that inexplicably connects him to Detective Lee Jae-Han. Everything “unbelievable” in his world changes. WHY? Lee Jae-Han is a dedicated but often overlooked officer. He is earnest, stubborn, and driven by a deep sense of justice. Those traits often put him at odds with corrupt superiors. He sounds normal. What’s so unbelievable about him? Uuhh … he happens to be working in 1989.

So? The year is 2015, but through the walkie-talkie, Park Hae-Young is speaking to Lee Jae-Han in 1989. OK! Let’s work together. We’re both in law enforcement. The two men begin exchanging information, each unaware at first of the full consequences of altering timelines. They collaborate to solve cold cases that have haunted Korea for decades.

♦ The Butterfly Effect

Cha Soo-Hyun is a present-day detective who once trained under Lee Jae-Han. He mysteriously disappeared, and she has never stopped searching for him. As Park Hae-Young and Lee Jae-Han exchange clues across time, they prevent tragedies, expose corruption, and reveal long-buried truths. But every change in the past ripples into the present. The altered timelines begin to shift the memories and experiences of Cha Soo-Hyun. The series explores the butterfly effect, showing how even small interventions can reshape lives.

As Lee Jae-Han digs deeper into systemic corruption, he becomes a target within his own department. His fate becomes a mystery. Is he alive, dead, or trapped in a timeline altered beyond recognition?

Park Hae-Young, meanwhile, evolves from a cynical profiler into someone who believes change is possible, even across time. His partnership with Lee Jae-Han becomes a surrogate mentor-student relationship. Both men bridge decades and reshape their destinies.

Ultimately, the crime-solving trio must confront the consequences of their time-altering actions. When they changed the past, did they save the future?

♦ The Trio Complement Each Other

Park Hae-Young: a lifetime of disappointment made him a skeptic.

“I don’t believe easily, but I can’t ignore the truth.”

Lee Jae-Han: uncompromising moral clarity when it comes to right and wrong.

“If no one else will do it, I will.”

Cha Soo-Hyun: steadfast and loyal, but rarely says what she feels directly; even when she’s breaking.

“I’ll endure it, because someone has to.”

They fill each other’s emotional gaps.

Park Hae-Young’s skepticism keeps the team grounded.
Lee Jae-Han’s idealism pushes the others to act.
Cha Soo-Hyun’s loyalty binds the timeline together.

Main Characters:

Park Hae-Young (played by Lee Je-Hoon, “The Art of Negotiation”, “Time to Hunt”, “Chief Detective 1958”, “Taxi Driver 1, 2 and 3”, “Move to Heaven”, “My Paparotti”, “An Ethics Lesson”, “Tomorrow With You”, “Escape”, “Collectors”, “Noryang: Deadly Sea”)
Lee Jae-Han (played by Cho Jin-Woong, “Believer 1 and 2”, “No Way Out: The Roulette”, ”’The Policeman’s Lineage”, “The Spy Gone North”, “Bluebeard“, “Nameless Gangster: Rules of The Time”, “Tree With Deep Roots”, “Chuno (The Slave Hunters)”)
Cha Soo-Hyun (played by Kim Hye-Soo, “Coin Locker Girl”, “Unmasked”, “Under The Queen’s Umbrella”, “Juvenile Justice”, “Hyena”, “Dr. Romantic”, “The Face Reader”, “The Thieves” )

Where to Watch: Netflix, Tubi TV, The Roku Channel, and Amazon Prime

Viewership and Rating:

IMDb: 8.5 out of 10 stars
My Drama List: 8.8 out of 10 stars
Common Sense Media: 4 out of 5 stars
Letterboxd: 4.2 out of 5 stars

My personal rating is the same as Letterboxd.

“Signal” is inspired by real-life criminal cases in South Korea, including the infamous Hwaseong serial murders. The K-drama is a masterfully woven crime-thriller that blends time-bending communication with gritty realism, anchored by three compelling leads whose lives intersect across decades. Is it any surprise there’s a sequel?