When her closest friend goes missing amid a series of gruesome wire-wrapped murders, a determined student struggles to uncover the truth behind the killings and the mysterious black substance left at each scene. As detectives hit dead ends and the body count rises, she must expose the dark secrets threatening Seoul in order to save her friend's life.

SYNOPSIS:

Haeri Min is a university student in Seoul living an ordinary life until her closest friend, Mina, vanishes without a trace. When Haeri reports her missing, the police dismiss her concerns, but Haeri knows something is deeply wrong.

Her fears are confirmed when news breaks of a horrific murder: a local man found wrapped in wire, his body discovered alongside a strange black substance that investigators cannot identify. Leading the investigation are Detective Kim and Detective Jaewha, seasoned Detectives who quickly realize this case is unlike anything they've encountered. As more bodies appear across Seoul, each victim bound in wire, each crime scene marked by the same inexplicable black residue the detectives find themselves at a complete dead end. The killer leaves no forensic evidence, no witnesses, no patterns they can trace.

And what is this strange Black ink?

Haeri becomes convinced that Mina's disappearance is connected to these murders. Unable to sit idle while the police investigation stalls, Haeri enlists her friends: Jaemin, Chaesoo and Yeonjun.

As the group retraces Mina's steps, they begin to notice strange events. Detective Kim and Detective Jaewha form an uneasy alliance with Haeri's group. Together, they discover the black substance isn't random; it's a signature connected to something nobody expected.

The investigation leads them into Seoul's hidden underbelly—abandoned subway tunnels, unground tunnels, and the dark corners where the city's past bleeds into its present. They uncover whispers of a secret that is just about to come alive.

As the body count rises and the wire-wrapped murders grow bolder, Haeri and her friends find themselves in the killer's crosshairs. Detective Kim and Detective Jaewha must decide how far they're willing to go to protect these students while pursuing a truth that could destroy their careers, or their lives. With Mina still missing, Haeri realizes that exposing Seoul's darkest secrets may be the only way to save her friend, even if it means none of them will survive to see justice served.

Silence in Seoul isn't golden, it's deadly.