Dramas like
Signal

The closest match in both premise and quality. A 1986 detective chasing a serial killer walks into 2017 and has to keep working the same case alongside the people it damaged. Same discipline about consequences, same conviction that a cold case is a moral debt. Difference: it is warmer and far kinder to its characters, which is either a relief or a loss depending on why you loved Signal.

Hooks early Episode 1. A 1986 detective lands in 2017 inside the first twenty minutes.

The other Kim Eun-hee, and the better-written show by most measures. A prosecutor who cannot feel and a police officer who feels everything, dismantling institutional corruption without a single wasted scene across sixteen hours. Difference: no genre element at all. The pleasure is procedural and cerebral rather than the ache of two timelines missing each other.

Hooks early Episode 2, once the first autopsy contradicts the official story.

For the plotting. Twenty episodes that rebuild themselves completely around episode twelve, off a serial-killer premise considerably nastier than Signal's. Difference: it is genuinely upsetting rather than merely tense, and it is more interested in grief than in the chase.

Hooks early Episode 2, once the killer and the two men chasing him are locked into the same story.

If what gripped you was not the radio but the men. Two policemen investigating each other in a town that would rather nothing were found, with a script that keeps relocating your suspicion. Difference: slower, smaller, entirely character-driven. There is no mechanism to solve, only people to finally understand.

Slow start Episode 3, the point at which you stop trusting both leads at once.

A modern profiler stranded in a 1988 precinct where nobody has heard of procedure. Same tension between two eras of policing and the same argument about whether justice actually improved. Difference: the mechanism that put him in 1988 is load-bearing rather than a given, so the fantasy asks more of you.

Hooks early Episode 2, once the 1988 precinct stops being a joke to him and starts being a place.

The historical-record version. Korea's first criminal profilers building a discipline against institutional contempt, in twelve cold, careful episodes. Difference: no gimmick, no time travel, no weekly payoff. It is restrained to the point of austerity, and the truest of these picks.

Hooks early Episode 2, once the first interview subject starts talking and the method becomes visible.

For the part of you that watched Signal wanting somebody punished properly. Episodic revenge on behalf of victims the system failed, delivered with real style. Difference: it is a fantasy in which the answer is violence, not an argument that the system could work. Much pulpier and much less careful.

Hooks early Episode 1. The format is fully established inside the first case.