Ten years ago, a brutal, unsolved murder shook the life of Yoon Yi-na, leaving her as the sole witness to a horrific crime. Trapped in the shadow of that unresolved trauma, Yi-na grows up determined to uncover the truth, ultimately forging a career as a top-tier criminal profiler for the police force. Her sharp intellect and uncanny ability to peer into the twisted minds of perpetrators make her an invaluable asset, yet her obsession with her past remains her driving, sometimes dangerous, motivation.Her meticulous world is suddenly upended when a series of bizarre, highly orchestrated murders begins terrorizing the city. Each gruesome crime scene is deliberately left with a cryptic, puzzle-like piece of evidence—a direct, taunting challenge addressed specifically to Yi-na. As the body count rises, the killer forces her to play a high-stakes psychological game where every solved riddle inches her closer to a terrifying reality.Enter Kim Han-saem, a tenacious, sharp-witted
homicide detective known for his unorthodox methods and fierce determination. Han-saem is initially assigned to partner with Yi-na, but he harbors deep skepticism regarding her emotional involvement in the case. Believing her personal history compromises her objectivity, Han-saem watches her every move. However, as the duo dives deeper into the labyrinthine investigation, they realize the current murders are inextricably linked to the unsolved tragedy of Yi-na’s youth.Together, Yi-na and Han-saem form an uneasy alliance, navigating a treacherous path filled with red herrings, psychological torment, and institutional corruption. The killer’s riddles do not merely point to physical clues; they expose dark secrets buried deep within the police department and Yi-na’s own fragmented memory. Every revelation blurs the line between hunter and hunted, forcing Yi-na to confront the horrific possibility that the person pulling the strings has been intimately close to her all along.As the final pieces of the puzzle converge, Yi-na must face her ultimate fear. The climax delivers a shocking confrontation that shatters her perception of the past. In a breathless
race against time, Yi-na and Han-saem must outsmart a mastermind whose ultimate endgame threatens not only their lives, but the very concept of justice itself, leading to a harrowing resolution that forever changes them both.