A Red Thread You Won’t Forget
I really enjoyed watching S Line. It’s a fresh, daring take on privacy and human connection wrapped in a dark thriller. The core concept is striking: people’s past sexual partners appear as glowing red lines above their heads, visible through special glasses. The show uses this premise to explore how society reacts when intimacy is suddenly public, and how obsession and judgment spiral into violence.
Hyun-heup (played by A Rin), who can naturally see these red lines without glasses, offers a unique perspective. Lee Soo-hyuk’s Han Ji-wook, a calm and emotionally restrained detective, grounds the narrative as the chaos intensifies. The production is visually compelling, especially with the symbolic use of the red lines and a haunting soundtrack that builds suspense throughout.
That said, the series struggles with pacing, especially from Episode 3 onwards. The suspense and momentum dip noticeably, and I found myself watching at 1.5x speed just to maintain the thriller’s intensity. This mid-series slowdown makes the story feel uneven, even though the tension returns toward the end.
One common criticism I’ve seen is disbelief that so many people in the story would resort to murder over the red lines. But in the show, it’s clear that the violence isn’t a spontaneous societal breakdown. It happens because Lee Da-hee’s character is handing these glasses to people who are already unstable or dangerous—those who would kill to protect their secrets or gain control. This explains the high death toll and violent conflicts, making it a story less about universal chaos and more about how dangerous tools fall into dangerous hands.
The finale divides viewers. Some felt it shifted too suddenly toward a dystopian, almost cult-like tone, which didn’t sit well with the build-up. This tonal shift felt jarring and left some narrative threads unresolved, leaving fans frustrated. It also felt like the final episode was less about wrapping up the story and more about setting up a possible second season.
Hyun-heup (played by A Rin), who can naturally see these red lines without glasses, offers a unique perspective. Lee Soo-hyuk’s Han Ji-wook, a calm and emotionally restrained detective, grounds the narrative as the chaos intensifies. The production is visually compelling, especially with the symbolic use of the red lines and a haunting soundtrack that builds suspense throughout.
That said, the series struggles with pacing, especially from Episode 3 onwards. The suspense and momentum dip noticeably, and I found myself watching at 1.5x speed just to maintain the thriller’s intensity. This mid-series slowdown makes the story feel uneven, even though the tension returns toward the end.
One common criticism I’ve seen is disbelief that so many people in the story would resort to murder over the red lines. But in the show, it’s clear that the violence isn’t a spontaneous societal breakdown. It happens because Lee Da-hee’s character is handing these glasses to people who are already unstable or dangerous—those who would kill to protect their secrets or gain control. This explains the high death toll and violent conflicts, making it a story less about universal chaos and more about how dangerous tools fall into dangerous hands.
The finale divides viewers. Some felt it shifted too suddenly toward a dystopian, almost cult-like tone, which didn’t sit well with the build-up. This tonal shift felt jarring and left some narrative threads unresolved, leaving fans frustrated. It also felt like the final episode was less about wrapping up the story and more about setting up a possible second season.
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