Detective Yifei finds herself ensnared in a relentless pursuit of the Red Ribbon Killer, a serial murderer who leaves their victims with crimson ribbons bound around their wrists. When another body surfaces bearing the killer's signature mark, Yifei's investigation takes an unexpected turn—she crosses paths with Leo, an enigmatic photographer shrouded in mystery and untold secrets. Despite his guarded nature, Leo's feelings for Yifei become undeniable, and he confesses his love with unexpected vulnerability. Yifei yields to his affections, yet her circle of trusted friends grows increasingly convinced that Leo himself may be the killer they're hunting. Torn between her convictions and mounting doubts, Yifei struggles to reconcile the man she's fallen for with the sinister possibility that he could be guilty. As suspicion creeps into her heart, Yifei must confront the dangerous question: can she trust her feelings, or has she fallen for a murderer?